Early this morning (my time) I got a notification from the Pacific Tsunami Warning Center that there was no tsunami threat from an M 7.2 earthquake in the Vanuatu Islands.
Tsunami Info Stmt: M7.2 Vanuatu Islands 0433PST Jan 8: Tsunami NOT expected; CA,OR,WA,BC,and AK
— NWS Tsunami Alerts (@NWS_NTWC) January 8, 2023
Later, as I woke up I checked the USGS website to see that there was an M7.0 earthquake offshore of the Vanuatu Islands.
https://earthquake.usgs.gov/earthquakes/eventpage/us7000j2yw/executive
Based on the depth of the hypocenter (the 3-D location of the earthquake) it appears that this M 7.0 ruptured a thrust fault within the Australia plate. Given the uncertainty of the location of the megathrust fault, it is possible that this actually was on the megathrust subduction zone fault (so is what we call an “interface” event). I don’t think that the USGS finite fault model is correct (it seems unlikely that this earthquake ruptured a fault within the Australia plate and slipped up into the upper plate). But I could be wrong (which is quite common).
I don’t always have the time to write a proper Earthquake Report. However, I prepare interpretive posters for these events.
Because of this, I present Earthquake Report Lite. (but it is more than just water, like the adult beverage that claims otherwise). I will try to describe the figures included in the poster, but sometimes I will simply post the poster here. (UPDATE: I could not resist spending a little time looking at updated papers from this region, so have included some figures below.)
Below is my interpretive poster for this earthquake
- I plot the seismicity from the past month, with diameter representing magnitude (see legend). I include earthquake epicenters from 1921-2021 with magnitudes M ≥ 3.0 in one version.
- I plot the USGS fault plane solutions (moment tensors in blue and focal mechanisms in orange), possibly in addition to some relevant historic earthquakes.
- A review of the basic base map variations and data that I use for the interpretive posters can be found on the Earthquake Reports page. I have improved these posters over time and some of this background information applies to the older posters.
- Some basic fundamentals of earthquake geology and plate tectonics can be found on the Earthquake Plate Tectonic Fundamentals page.
I include some inset figures.
Some Supporting Information
- Here is the USGS poster showing the seismicity for this region from 1900-2010 (Benz et al., 2011). Below I include the legend (not the correct scale; click on this link for the entire poster (65 MB pdf)). Note the cross section F-F’ which I plot on the poster above.
- Here is the cross section F-F’ again, with the legend below.
- Here are some figures from Bergeot et al., 2009.
- This first figure shows the tectonic setting and the plate convergence rates (the rates, in mm/year, that the Australia plate is converging relative to the North Fiji Basin.
- This figure shows the horizontal motion rates (in mm/year) for the GPS sites in the region.
- This figure shows a map where they plot, in the next figure, a comparison between their modeled vertical velocities with the observed vertical velocities.
- This figure shows the comparison between their modeled velocities and the observed velocities.
(a) Geodynamic setting of the VSZ, with block motions relative to the North Fiji Basin [from Calmant et al., 2003]. The Vanuatu arc is split into three blocks, with anticlockwise rotation (north), convergence (center), and clockwise rotation (south). Dashed line is the BATB; solid lines are the spreading ridge; bold line is the VSZ. Bathymetry data are from Calmant et al. [2002]. The black rectangle is the central part of the Vanuatu arc. White arrows are velocities (millimeters per year) with respect to the Australian plate (AP); black arrows are block motion with respect to the North Fiji Basin. Dotted line is the cross section of Figure 2b. (b) Schematic of the central part of the VSZ [from Lagabrielle et al., 2003]. The direction of this cross section is west to east, and it intersects the Santo and Maewo Islands (dotted line in Figure 2a). Abbreviations are as follows: IAB, Aoba Intra-arc Basin; BATB, back-arc thrust belt; NFB, North Fiji Basin.
Horizontal interseismic GPS velocities for the VSZ in an Australia-fixed reference frame. The Australian motion is estimated as a rigid rotation from our GPS results with a least squares inversion. Abbreviations are as follows: WTP, West Torres Plateau; DER, D’Entrecasteaux Ridge. Lines are (1) BATB, (2) spreading ridge, (3) VSZ, (4) discontinuity supposed between TGOA and Epi island, and (5) transition zone.
Transects and GPS stations used to assess the locked zone parameters in this study. Shaded triangles represent the A-A0 (TNMR, LVMP, LMBU, WLRN, SWBY, VMVS, NSUP, RNSR, and AMBR) transect GPS stations, and solid triangles represent the B-B0 transect GPS stations (LISB, TASM, AVNA, RATA, RATU, SANC, AOBA, PNCT, and MAWO). The bold lines represent the A-A0 and B-B0 transects. The white arrows show the convergence direction. Abbreviations are as follows: DER, D’Entrecasteaux Ridge; WTP, Wet Torres Plateau. The stars indicate the edge of the locked zone as deduced from the GPS velocity interpretation (Figure 12). Lines are (1) BATB and (2) VSZ.
(top) Vertical and (bottom) horizontal (perpendicular to the trench) velocity profiles for the GPS stations of the A-A0 (open circle) and B-B0 (filled circle) transects. Distances are given with respect to the trench. The bold curves represent the best fit of the locked zone and long-term convergence rate model (dip, 20; width, 50 km; slip, 54 mm a1) estimated from observed velocities. Lines 2 and 3 represent the effect of the width variation in the model (45 and 60 km, respectively). See Figure 11 for the transect location.
- Here are the two figures from Cleveland et al. (2014).
- Figure 1. I include the figure caption below as a blockquote.
- Figure 17. I include the figure caption below as a blockquote.
- Figure 17. I include the figure caption below as a blockquote.
(left) Seismicity of the northern Vanuatu subduction zone, displaying all USGS-NEIC earthquake hypocenters since 1973. The Australian plate subducts beneath the Pacific in nearly trench-orthogonal convergence along the Vanuatu subduction zone. The largest events are displayed with dotted outlines of the magnitude-scaled circle. Convergence rates are calculated using the MORVEL model for Australia Plate relative to Pacific Plate [DeMets et al., 2010]. (right) All GCMT moment tensor solutions and centroids for Mw ≥ 5 since 1976, scaled with moment. This region experiences abundant moderate and large earthquakes but lacks any events with Mw >8 since at least 1900.
One hundred day aftershock distributions of all earthquakes listed in the ISC catalog for the 1966 sequence and in the USGS-NEIC catalog for the 1980, 1997, 2009, and 2013 sequences in northern Vanuatu. The 1966 main shocks are plotted at locations listed by Tajima et al. [1990]. Events of the 1997 and 2009 sequences were relocated using the double difference method [Waldhauser and Ellsworth, 2000] for P wave first arrivals based on EDR picks. The event symbol areas are scaled relative to the earthquake magnitudes based on a method developed by Utsu and Seki [1954]. Hypocenters of most aftershock events occurred at <50 km depth.
(right) Space-time plot of shallow (≤ 70 km) seismicity M ≥ 5.0 in northern Vanuatu recorded in the NEIC catalog as a function of distance south of ~10°N, 165.25°E. (left) The location of the seismicity on a map rotated to orient the trench vertically.
- Craig et al. (2014) evaluated the historic record of seismicity for subduction zones globally. In particular, the evaluated the relations between upper and lower plate stresses and earthquake types (cogent for the southern New Hebrides trench). Below is a figure from their paper for this part of the world. I include their figure caption below in blockquote.
Outer-rise seismicity along the New Hebrides arc. (a) Seismicity and focal mechanisms. Seismicity at the southern end of the arc is dominated by two major outer-rise normal faulting events, and MW 7.6 on 1995 May 16 and an MW 7.1 on 2004 January 3. Earthquakes are included from Chapple & Forsyth (1979); Chinn & Isacks (1983); Liu & McNally (1993). (b) Time versus latitude plot.
- Here is a summary figure from Craig et al. (2014) that shows different stress configurations possibly existing along subduction zones.
Schematic diagram for the factors influencing the depth of the transition from horizontal extension to horizontal compression beneath the outer rise. Slab pull, the interaction of the descending slab with the 660 km discontinuity (or increasing drag from the surround mantle), and variations in the interface stress influence both the bending moment and the in-plane stress. Increases in the angle of slab dip increases the dominance of the bending moment relative to the in-plane stress, and hence moves the depth of transition towards the middle of the mechanical plate from either an shallower or a deeper position. A decrease in slab dip enhances the influence of the in-plane stress, and hence moves the transition further from the middle of the mechanical plate, either deeper for an extensional in-plane stress, or shallower for a compressional in-plane stress. Increased plate age of the incoming plate leads to increases in the magnitude of ridge push and intraplate thermal contraction, increasing the in-plane compressional stress in the plate prior to bending. Dynamic topography of the oceanic plate seawards of the trench can result in either in-plane extension or compression prior to the application of the bending stresses.
- Here are the figures from Richards et al. (2011) with their figure captions below in blockquote.
- Here is the map showing the current configuration of the slabs in the region.
- This is the cross section showing the megathrust fault configuration based on seismic tomography and seismicity.
- Here is their time step interpretation of the slabs that resulted in the second figure above.
- Here are two great figures from Deng et al. (2022). This article focuses on the influence of the D’Entrecasteaux Ridge on subduction here in Vanuatu. They focus on geochemical data from magmatic rocks in the area.
- This one shows a variety of processes going on in this area.
- Here is a video that shows a simulation from Deng et al. (2022).
- Baillard et al. (2015) provide some insight into the geometry of the Australia plate slab. I am adjusting my hypothesis to be that this M 7.0 probably was on the megathrust, based on their work.
- This first figure shows a map and some cross sections.
- Note how cross section 4 is really close to the M 7.0. This geometry places the top of the slab below the M 7.0 hypocenter.
- This figure shows how they interpret the seismicity in this area.
- This figure shows some specific earthquakes they used in their analyses. Earthquake 1 (pink) is really close to the M 7.0. They interpret that event to be in the upper part of the Australia plate. At this point, I suggest that it is equivocal, about whether or not the M 7.0 was an interface event or a slab or crustal event.
Map showing distribution of slab segments beneath the Tonga-Vanuatu region. West-dipping Pacifi c slab is shown in gray; northeast-dipping Australian slab is shown in red. Three detached segments of Australian slab lie below the North Fiji Basin (NFB). HFZ—Hunter Fracture Zone. Contour interval is 100 km. Detached segments of Australian plate form sub-horizontal sheets located at ~600 km depth. White dashed line shows outline of the subducted slab fragments when reconstructed from 660 km depth to the surface. When all subducted components are brought to the surface, the geometry closely approximates that of the North Fiji Basin.
Previous interpretation of combined P-wave tomography and seismicity from van der Hilst (1995). Earthquake hypocenters are shown in blue. The previous interpretation of slab structure is contained within the black dashed lines. Solid red lines mark the surface of the Pacifi c slab (1), the still attached subducting Australian slab (2a), and the detached segment of the Australian plate (2b). UM—upper mantle;
TZ—transition zone; LM—lower mantle.
Simplifi ed plate tectonic reconstruction showing the progressive geometric evolution of the Vanuatu and Tonga subduction systems in plan view and in cross section. Initiation of the Vanuatu subduction system begins by 10 Ma. Initial detachment of the basal part of the Australian slab begins at ca. 5–4 Ma and then sinking and collision between the detached segment and the Pacifi c slab occur by 3–4 Ma. Initial opening of the Lau backarc also occurred at this time. Between 3 Ma and the present, both slabs have been sinking progressively to their current position. VT—Vitiaz trench; dER—d’Entrecasteaux Ridge.
Geological and geophysical constraints regarding the evolution of the Vanuatu arc. (a) Bathymetric map showing the locations of islands for which samples were included in our geochemical compilation. Slab dip contours below the Vanuatu arc are displayed every 20° (from Hayes et al., 2018). (b) Bathymetric map of the Vanuatu arc and an inset showing depth-to-slab versus distance-from-trench for each of the sample localities included in our compilation (Table S1 in Supporting Information S1). Slab depth contours beneath the Vanuatu arc are displayed every 20 km (from Hayes et al., 2018). The orange lines show the chosen cross sections (i.e., Sections A, B, C) across the different blocks of the Vanuatu arc, which were used to estimate slab dips. Orange dots denote the location of Deep Sea Drilling Project Site 286 and Ocean Drilling Program Legs 134 Sites 828 and 831. (c) Interpreted geodynamic setting of the Vanuatu arc based on modern global positioning system velocity measurements (observed, black arrows; modeled, white arrows; from Bergeot et al., 2009). The Vanuatu arc can be divided into three tectonic blocks that are separated by two strike-slip faults (magenta dashed lines; Calmant et al., 2003; Taylor et al., 1995), which are the counterclockwise rotated Northern Block, the eastward migrated Central Block and the clockwise rotated Southern Block. Orange arrows indicate plate convergence velocities (in mm/year) with respect to the Australian plate (Bergeot et al., 2009). (d) Intermediate-depth seismicity distribution (50–170 km) since 1972 with magnitudes in the range of 4–7, from USGS Earthquake Catalog (https://earthquake.usgs.gov/earthquakes/search/). The seismic gap is highlighted by a solid polygon. The wide red arrow depicts the influx of hot sub-slab mantle to the forearc mantle wedge through a slab tear.
Schematic of the Vanuatu subduction zone to illustrate the model proposed by this study. The conceptual model highlights the role that the subducting buoyant D’Entrecasteaux ridge plays in the dynamic evolution of the Vanuatu arc. The introduction of D’Entrecasteauz Ridge causes shallow subduction and the development of a slab tear south of the ridge and the segmentation of the Vanuatu arc into the Northern Block, Central Block and Southern Block. Shallow slab subduction beneath the Central Block results in (a) squeezing out of the asthenospheric mantle; (b) scraping off the bottom of the ancient continental lithospheric mantle beneath the forearc, which then migrates ahead of the advancing slab and forms a bulldozed keel underneath the main-arc and (c) transmitting compressional stresses in the over-riding plate, which inhibits the formation of backarc spreading and instead produces a backarc thrust belt. Additionally, the ingression of hot subslab mantle causes partial melting of the cold forearc mantle and produces magmatism anomalously close to the trench (i.e., the Efate, Nguna, and Pele volcanoes that are situated in the forearc).
Geometry of the subduction interface and updip/downdip extents of the seismogenic zone. (a) Map view. The green contour is at 27 km depth and marks the intersection with the fore-arc Moho. The dashed contours present the updip and downdip extents of the seismogenic zone. The numbered lines showthe location of cross sections plotted to the right. NDR: north d’Entrecasteaux ridge; BS: Bougainville seamount. (b) Geometric cross sections of the subduction interface (depth as a function of distance from the subduction front). (c) Dip cross sections (dip angle as a function of distance from the subduction front).
Cross section of seismic activity through the center of our total catalog (only events with residuals <0.2 s are plotted). Three clusters of activity are observed: (1) around the subduction interface (green), (2) within the subducting plate beneath the subduction interface (red), and (3) at intermediate depths (blue). The dotted line is our interpretation of the subduction interface.
Clusters and focal mechanisms in the local catalog. Simple focal mechanisms are illustrated in black, composite focal mechanisms in colors corresponding to the cluster events (circles). P axes indicated in red. (a) Map view. The boxes indicate the orientation and dimensions of the cross sections. (b) Cross section beneath Santo Island. (c) Cross section between Santo and Malekula Islands. The cross sections also show the picked subduction interface (thick black curve), the Australian Plate Moho (dotted line, assuming a 8 km thick crust), and the North Fiji Basin Moho (dotted line, assuming a 27 km thick fore-arc crust).
- 2023.01.08 M 7.0 Vanuatu Islands (poster)
- 2022.11.22 M 7.0 Solomon Isles
- 2022.11.11 M 7.3 Tonga
- 2022.09.10 M 7.6 Papua New Guinea
- 2021.03.04 M 8.1 Kermadec
- 2021.02.10 M 7.7 Loyalty Islands
- 2019.06.15 M 7.2 Kermadec
- 2019.05.14 M 7.5 New Ireland
- 2019.05.06 M 7.2 Papua New Guinea
- 2018.12.05 M 7.5 New Caledonia
- 2018.10.10 M 7.0 New Britain, PNG
- 2018.09.09 M 6.9 Kermadec
- 2018.08.29 M 7.1 Loyalty Islands
- 2018.08.18 M 8.2 Fiji
- 2018.03.26 M 6.9 New Britain
- 2018.03.26 M 6.6 New Britain
- 2018.03.08 M 6.8 New Ireland
- 2018.02.25 M 7.5 Papua New Guinea
- 2018.02.26 M 7.5 Papua New Guinea Update #1
- 2017.11.19 M 7.0 Loyalty Islands Update #1
- 2017.11.07 M 6.5 Papua New Guinea
- 2017.11.04 M 6.8 Tonga
- 2017.10.31 M 6.8 Loyalty Islands
- 2017.08.27 M 6.4 N. Bismarck plate
- 2017.05.09 M 6.8 Vanuatu
- 2017.03.19 M 6.0 Solomon Islands
- 2017.03.05 M 6.5 New Britain
- 2017.01.22 M 7.9 Bougainville
- 2017.01.03 M 6.9 Fiji
- 2016.12.17 M 7.9 Bougainville
- 2016.12.08 M 7.8 Solomons
- 2016.10.17 M 6.9 New Britain
- 2016.10.15 M 6.4 South Bismarck Sea
- 2016.09.14 M 6.0 Solomon Islands
- 2016.08.31 M 6.7 New Britain
- 2016.08.12 M 7.2 New Hebrides Update #2
- 2016.08.12 M 7.2 New Hebrides Update #1
- 2016.08.12 M 7.2 New Hebrides
- 2016.04.06 M 6.9 Vanuatu Update #1
- 2016.04.03 M 6.9 Vanuatu
- 2015.03.30 M 7.5 New Britain (Update #5)
- 2015.03.30 M 7.5 New Britain (Update #4)
- 2015.03.29 M 7.5 New Britain (Update #3)
- 2015.03.29 M 7.5 New Britain (Update #2)
- 2015.03.29 M 7.5 New Britain (Update #1)
- 2015.03.29 M 7.5 New Britain
- 2015.11.18 M 6.8 Solomon Islands
- 2015.05.24 M 6.8, 6.8, 6.9 Santa Cruz Islands
- 2015.05.05 M 7.5 New Britain
New Britain | Solomon | Bougainville | New Hebrides | Tonga | Kermadec Earthquake Reports
General Overview
Earthquake Reports
- Frisch, W., Meschede, M., Blakey, R., 2011. Plate Tectonics, Springer-Verlag, London, 213 pp.
- Hayes, G., 2018, Slab2 – A Comprehensive Subduction Zone Geometry Model: U.S. Geological Survey data release, https://doi.org/10.5066/F7PV6JNV.
- Holt, W. E., C. Kreemer, A. J. Haines, L. Estey, C. Meertens, G. Blewitt, and D. Lavallee (2005), Project helps constrain continental dynamics and seismic hazards, Eos Trans. AGU, 86(41), 383–387, , https://doi.org/10.1029/2005EO410002. /li>
- Jessee, M.A.N., Hamburger, M. W., Allstadt, K., Wald, D. J., Robeson, S. M., Tanyas, H., et al. (2018). A global empirical model for near-real-time assessment of seismically induced landslides. Journal of Geophysical Research: Earth Surface, 123, 1835–1859. https://doi.org/10.1029/2017JF004494
- Kreemer, C., J. Haines, W. Holt, G. Blewitt, and D. Lavallee (2000), On the determination of a global strain rate model, Geophys. J. Int., 52(10), 765–770.
- Kreemer, C., W. E. Holt, and A. J. Haines (2003), An integrated global model of present-day plate motions and plate boundary deformation, Geophys. J. Int., 154(1), 8–34, , https://doi.org/10.1046/j.1365-246X.2003.01917.x.
- Kreemer, C., G. Blewitt, E.C. Klein, 2014. A geodetic plate motion and Global Strain Rate Model in Geochemistry, Geophysics, Geosystems, v. 15, p. 3849-3889, https://doi.org/10.1002/2014GC005407.
- Meyer, B., Saltus, R., Chulliat, a., 2017. EMAG2: Earth Magnetic Anomaly Grid (2-arc-minute resolution) Version 3. National Centers for Environmental Information, NOAA. Model. https://doi.org/10.7289/V5H70CVX
- Müller, R.D., Sdrolias, M., Gaina, C. and Roest, W.R., 2008, Age spreading rates and spreading asymmetry of the world’s ocean crust in Geochemistry, Geophysics, Geosystems, 9, Q04006, https://doi.org/10.1029/2007GC001743
- Pagani,M. , J. Garcia-Pelaez, R. Gee, K. Johnson, V. Poggi, R. Styron, G. Weatherill, M. Simionato, D. Viganò, L. Danciu, D. Monelli (2018). Global Earthquake Model (GEM) Seismic Hazard Map (version 2018.1 – December 2018), DOI: 10.13117/GEM-GLOBAL-SEISMIC-HAZARD-MAP-2018.1
- Silva, V ., D Amo-Oduro, A Calderon, J Dabbeek, V Despotaki, L Martins, A Rao, M Simionato, D Viganò, C Yepes, A Acevedo, N Horspool, H Crowley, K Jaiswal, M Journeay, M Pittore, 2018. Global Earthquake Model (GEM) Seismic Risk Map (version 2018.1). https://doi.org/10.13117/GEM-GLOBAL-SEISMIC-RISK-MAP-2018.1
- Zhu, J., Baise, L. G., Thompson, E. M., 2017, An Updated Geospatial Liquefaction Model for Global Application, Bulletin of the Seismological Society of America, 107, p 1365-1385, https://doi.org/0.1785/0120160198
- Baillard, C., W. C. Crawford, V. Ballu, M. Régnier, B. Pelletier, and E. Garaebiti (2015), Seismicity and shallow slab geometry in the central Vanuatu subduction zone, J. Geophys. Res. Solid Earth,120,5606–5623, https://doi.org/10.1002/2014JB011853
- Benz, H.M., Herman, Matthew, Tarr, A.C., Furlong, K.P., Hayes, G.P., Villaseñor, Antonio, Dart, R.L., and Rhea, Susan, 2011. Seismicity of the Earth 1900–2010 eastern margin of the Australia plate: U.S. Geological Survey Open-File Report 2010–1083-I, scale 1:8,000,000.
- Bergeot, N., M. N. Bouin, M. Diament, B. Pelletier, M. Re´gnier, S. Calmant, and V. Ballu (2009), Horizontal and vertical interseismic velocity fields in the Vanuatu subduction zone from GPS measurements: Evidence for a central Vanuatu locked zone, J. Geophys. Res., 114, B06405, https://doi.org/10.1029/2007JB005249
- Cleveland, K.M., Ammon, C.J., and Lay, T., 2014. Large earthquake processes in the northern Vanuatu subduction zone in Journal of Geophysical Research: Solid Earth, v. 119, p. 8866-8883, doi:10.1002/2014JB011289.
- Deng, C., Jenner, F. E., Wan, B., & Li, J.-L. (2022). The influence of ridge subduction on the geochemistry of Vanuatu arc magmas. Journal of Geophysical Research: Solid Earth, 127, e2021JB022833. https://doi.org/10.1029/2021JB022833
- Hayes, G. P., D. J. Wald, and R. L. Johnson, 2012. Slab1.0: A three-dimensional model of global subduction zone geometries, J. Geophys. Res., 117, B01302, doi:10.1029/2011JB008524.
- Richards, S., Holm., R., Barber, G., 2011. When slabs collide: A tectonic assessment of deep earthquakes in the Tonga-Vanuatu region, Geology, v. 39, pp. 787-790.
- Bumba Crossing Kevin MacLeod (incompetech.com) | Licensed under Creative Commons: By Attribution 3.0 License | http://creativecommons.org/licenses/by/3.0/
References:
Basic & General References
Specific References
Oceanic-Oceanic Subduction Zone Figure
Music Reference (in 1900-2016 seismicity video)
Social Media
#EarthquakeReport for M7.0 #Earthquake in #Vanuatu
Felt intensity MMI 7
Read more about regional tectonics in 2017 reporthttps://t.co/Nvbes3IH0Lhttps://t.co/DbR3abwbKC pic.twitter.com/0Yjc8ywQVA
— Jason "Jay" R. Patton (@patton_cascadia) January 8, 2023
#EarthquakeReport for the M 7.0 #Earthquake offshore of #Vanuatu
high intensity felt (MMI 7.8)
no observed tsunami on tide gages
read more in the reporthttps://t.co/gcdHfboaF5 pic.twitter.com/ySQT4lXgQS
— Jason "Jay" R. Patton (@patton_cascadia) January 8, 2023
Notable quake, preliminary info: M 7.2 – 38 km WSW of Port-Olry, Vanuatu https://t.co/35aMQ7mTt7
— USGS Earthquakes (@USGS_Quakes) January 8, 2023
The waves from the M7.0 earthquake near Vanuatu are passing under me on the east coast of the US right now!
Look carefully at the scale on the 2nd image – by the time they reach VA these waves are about 1/2 the width of a human hair so far too small to feel. 1/n pic.twitter.com/q56UWKN6WA
— Wendy Bohon, PhD 🌏 (@DrWendyRocks) January 8, 2023
Waves from the M7.0 earthquake in Vanuatu shown on a nearby station using Station Monitor. https://t.co/Tir0KZELXN pic.twitter.com/JUey79Uizv
— EarthScope Consortium (@EarthScope_sci) January 8, 2023
Back projection for the M7.0 earthquake in Vanuatuhttps://t.co/j6otX26QHa pic.twitter.com/wiVXSX7iop
— EarthScope Consortium (@EarthScope_sci) January 8, 2023
One hour ago, M7.0 #earthquake in the Espiritu Santo island, Vanuatu. Very shallow!https://t.co/2cwp078v1N pic.twitter.com/wqrjbGSwMN
— José R. Ribeiro (@JoseRodRibeiro) January 8, 2023
Preliminary M6.9 #Earthquake
ID: #rs2023anvawm
90km/56miles from #Luganville, in #VanuatuIslands
2023-01-08 12:32 UTC@raspishake networkJoin the largest #CitizenScience #seismograph community ➡ https://t.co/Y5O0dgJqJF
EVENT ➡ https://t.co/wk0tSVfL2i pic.twitter.com/NjEfzppBQE
— Raspberry Shake Earthquake Channel (@raspishakEQ) January 8, 2023
No #tsunami threat to Australia from magnitude 6.9 #earthquake near Vanuatu Islands. Latest advice at https://t.co/Tynv3ZQpEq. pic.twitter.com/eoxJwLiQbo
— Bureau of Meteorology, Australia (@BOM_au) January 8, 2023
The eastern margin of the Australia plate is so sesimically active due to high rates of convergence between the Australia and Pacific plates. You can view earthquakes in this area (and around the world) in 3D using the IRIS Earthquake Browser, like I’ve done here. pic.twitter.com/KBRtwCagcl
— Wendy Bohon, PhD 🌏 (@DrWendyRocks) January 8, 2023
Schweres gefährliches Erdbeben im Norden von Vanuatu: Tsunami-Warnung https://t.co/1RRYtpqeKx pic.twitter.com/3I6S2KfGCA
— Erdbebennews (@Erdbebennews) January 8, 2023
Today 7.0 Mw Central #VANUATU🇻🇺, ruptured at ~23 km depth along the subduction\megathrust fault (associated to the d'Entrecasteaux Zone).
Tecto-schematic 3D figure from :
🔹The Influence of Ridge Subduction on the Geochemistry of Vanuatu Arc Magmas (2022)https://t.co/ykBd2L4myK pic.twitter.com/mFNDdrTkvY— Abel Seism🌏Sánchez (@EQuake_Analysis) January 8, 2023
The M7.0 earthquake in Vanuatu occurred at a depth of ~28 km in a seismically active area that experiences frequent large earthquakes. Earthquakes in this region are caused by the Australian Plate subducting under the Pacific Plate.https://t.co/OM7bvJKw7W pic.twitter.com/xq9NfDJTiX
— EarthScope Consortium (@EarthScope_sci) January 8, 2023
Global surface and body wave sections from the M7.0 earthquake in Vanuatuhttps://t.co/60idTVV9BN pic.twitter.com/6gJaLM01LZ
— EarthScope Consortium (@EarthScope_sci) January 8, 2023
I cannot confirm this is from today’s earthquake:
Return to the Earthquake Reports page.
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- Sorted By Region
Well, it has been a very busy week. I had gotten back from the American Geophysical Union Fall Meeting in Chicago late Saturday night. I had one day to hang out with my cats before I was to head down to Santa Cruz to meet with the city there to discuss installing a tide gage. Santa Cruz lacks a gage yet receives large tsunami inundations. So, I drove down and got there about 10pm Monday evening. I was up for an hour or two and went to sleep. At shortly after 2:30am I got a text message about a M 6.4 earthquake near Ferndale. I immediately got up and texted my colleague Cynthia Pridmore. We are tasked to prepare Earthquake Quick Reports that we (California Geological Survey, CGS) provide to the California Governor’s Office of Emergency Services (Cal OES). These reports provide technical information that helps them provide resources to local first responders during times following natural hazards impacts. https://earthquake.usgs.gov/earthquakes/eventpage/nc73821036/executive These reports are reviewed by the head of the Seismic Hazards Program (Tim Dawson) and by the State Geologist prior to being provided to the leadership in our organization and parent organizations. Reports for larger earthquakes and tsunami sometimes end up on the Governor’s desk. We got our report submitted within about 45 minutes and we prepared for a long couple of days. We at CGS met at 8am to discuss our field response activities. CGS and the U.S. Geological Survey (USGS) work closely together to document field evidence from earthquakes and tsunami. Kate Thomas (CGS) and Luke Blair (USGS) have a database ready to go within about 15 minutes after an earthquake. This database is used on mobile devices to collect observational information that include photos and other information. We use the ESRI Field Maps app for this purpose. We decided to send CGS staff from the Eureka office out to collect information. I was to drive back to Humboldt and then join the field teams the following day. Something that also happens following significant or damaging earthquakes is the activation of the California Earthquake Clearinghouse. Pridmore (CGS) is the chair of the EQCH and works with our partners (USGS, EERI, etc.) to decide when to activate the EQCH. Data from these CGS/USGS field observations, along with data from other field teams, are posted onto the EQCH page for this event. Here is where those data are made available for this M 6.4 Ferndale Earthquake. The dataset of field observations are posted on that page are found by clicking on the “Resources” tab, also linked here. When I returned to my home, the power was still out. We (CGS) had a scheduled meeting at 6pm and the EQCH meeting at 7pm. So, I went to the Eureka National Weather Service (NWS) Office on Woodley Island. They have electric power backup and satellite internet access. I work closely with the NWS and Cal OES and have been granted access to set up my workstation there during natural hazard emergencies like earthquake and tsunami. This was we can all better coordinate our actions without the burden of having power or internet outages at our residences. We are thankful for these relationships between CGS, the NWS (Ryan Aylward, Troy Nicolini) and Cal OES Eureka (Todd Becker). So, I got up very early to work with my co-workers to continue the field investigations. There was little geological evidence from the earthquake. We identified some landslides and cracks in road fill. We did not locate any evidence for liquefaction, even though the USGS liquefaction susceptibility data suggested a high chance for that phenomena. This earthquake is in a tectonically complicated region of the western United States, the Mendocino triple junction. Here, three plate boundary fault systems meet (the definition of a triple junction): the San Andreas fault from the south, the Cascadia subduction zone from the north, and the Mendocino fault from the west. These plate boundary fault systems all overlap like fingers do when we fold our hands together. The Cascadia subduction zone is a convergent (moving together) plate boundary where the Gorda and Juan de Fuca plates dive into the Earth beneath the North America plate. The fault formed here is called the megathrust subduction zone fault. Earthquakes on subduction zone faults generate the largest magnitude earthquakes of all fault types and also generate tsunami that can impact the local area and also travel across the ocean to impact places elsewhere. The most recent known Cascadia megathrust subduction zone fault earthquake was in January 1700. The San Andreas and Mendocino fault systems are strike-slip (plates move side by side) fault systems. Many are familiar with the 1906 San Francisco Earthquake. While the largest source of annual seismicity are intraplate Gorda plate earthquakes, the two largest contributors to seismic hazards in California are the Cascadia subduction zone (CSZ) and the San Andreas fault (SAF) systems. These sources overlap in the region of the Mendocino triple junction (MTJ) and may interact in ways we are only beginning to understand as evidenced by the 2016 M7.8 Kaikōura earthquake in New Zealand (Clark et al., 2017 Litchfield et al., 2018), which occurred along a similar subduction/transform boundary, and included co-seismic rupture of more than 20 faults. The M 6.4 earthquake was a strike-slip earthquake within the downgoing Gorda plate (an intra plate earthquake). The earthquake started offshore and then the fault slipped to the east. There is modest evidence that this earthquake generated focused seismic waves in the direction of fault slip (this is called directivity). In addition, the area of the lower Eel River Valley is a sedimentary basin. Sedimentary basins are known for amplifying ground shaking and trapping seismic waves, further increasing the ground shaking. The lower Eel River Valley is formed by tectonic folding caused by the northward migration of the Mendocino triple junction (read my contributions in the 2022 Pacific Cell Friends of the Pleistocene guidebook for more information about the structure of the Eel River and Van Duzen River valleys and surrounding regions. So the seismic waves could have been trapped in the sedimentary basin formed within the Eel River Valley. However, there is an even older sedimentary basin here in which the Eel/Van Duzen river sediments are deposited within. These older sedimentary rocks have different seismic velocity properties that could also affect how seismic waves are transmitted here. There is a terrane bounding fault that separates these older rocks (Cretaceous Franciscan Formation) to the south from the younger rocks (Quaternary-Tertiary Wildcat Group) to the north. Also, any of the large crustal fault systems (e.g., the Russ fault, the Little Salmon or Table Bluff faults, etc.) could guide seismic waves (a.k.a. act as wave guides), directing them in orientations relative to the fault systems. My leading hypothesis is that the younger (latest Pleistocene to Holocene) river sediments that form the younger sedimentary basin and the crustal faults are both responsible for modifying the seismic wave transmission from this earthquake. One thing people alkmost always ask si about whether or not ther eis a higher chance that there wil eb a Cascadia subduciton zone earthquake. This is currently impossible to tell. However, we can make some estimates of how forces within the Earth might have changed after a given earthquake. There was a Gorda plate earthquake sequence in 2018 that allowed us to consider these changes in the crust to see if the megathrust was brought more close to rupture. Here is the report from that Gorda plate earthquake sequence. I will update this report further in the future, as we collect additional information. One last thing for now. Bob McPherson formed a research group that we call Team Gorda. Team Gorda, supported by Connie Stewart at Cal Poly Humboldt, is using recently constructed fiber cables as a seismic instrument (called distributed acoustic seismic, DAS) to learn more about the underlying tectonic structures in the region. This fiber cable acts as thousands of little seismometers. Jeff McGuire and his team just installed the interrogator in our office at the Arcata City Hall. Horst from the Berkeley Seismic Lab is also working with Bob to install seismometers along the fiber cable so that we can calibrate the DAS observations. We ran our first DAS experiment earlier this year and plan on doing more experiments far into the future, including fiber cables that are installed from here into the Pacific Ocean (on their way to Asia). What is an earthquake? What causes earthquakes and where do they happen? How are earthquakes recorded and measured? Learn more about 'The Science of Earthquakes' at: https://t.co/JAQv4cc2KC pic.twitter.com/pJ2IfQ76bs — USGS Earthquakes (@USGS_Quakes) January 4, 2023
Block rotation model for the central Cascadia forearc. SeaBeam bathymetry shaded from the north. The Wecoma and Daisy Bank faults are show, with the Daisy Bank fault exposed in the foreground. Well-mapped fault traces are in solid; discontinuous traces are dashed. The arc-parallel component of oblique subduction creates a dextral share couple, which is accommodated by WNW trending left-lateral strike-slip faults. We propose that shearing of the slab due to oblique subduction is responsible for the fault involving oceanic crust. WF, Wecoma fault; DBF, Daisy bank fault; FF, Fulmar fault, “pr,” pressure ridge; “DB,” Daisy Bank; “OT?,” possible old left-lateral fault strand. Arrow heads and tails show strike-slip motion. White arrows at western end of Wecoma fault show eastward increasing slip calculated from isopach offsets.
Coseismic displacements from the 15-Jun-2005 M7.2 Gorda plate earthquake located (off the map) 156 km (97 miles) W (280°) from Trinidad, CA and 157 km (98 miles) WSW (251°) from Crescent City, CA. Note the similarity to the deformation pattern of the 1994 event. Continuously operating GPS stations shown here are operated and maintained through the Plate Boundary Observatory component (pboweb.unavco. org) of the National Science Foundation’s EarthScope project
The Gorda and Juan de Fuca plates subduct beneath the North America plate to form the Cascadia subduction zone fault system. In 1992 there was a swarm of earthquakes with the magnitude Mw 7.2 Mainshock on 4/25. Initially this earthquake was interpreted to have been on the Cascadia subduction zone (CSZ). The moment tensor shows a compressional mechanism. However the two largest aftershocks on 4/26/1992 (Mw 6.5 and Mw 6.7), had strike-slip moment tensors. In my mind, these two aftershocks aligned on what may be the eastern extension of the Mendocino fault. However, looking at their locations, my mind was incorrect. These two earthquakes were not aftershocks, but were either left-lateral or right-lateral strike-slip Gorda plate earthquakes triggered by the M 7.1 thrust event. These two quakes appear to be aligned with the two northwest trends in seismicity and the 18 March 2020 M 5.2. The orientation of the mechanisms are not as perfectly well aligned, but there are lots of reasons for this (perhaps the faults were formed in a slightly different orientation, but have rotated slightly). There have been several series of intra-plate earthquakes in the Gorda plate. Two main shocks that I plot of this type of earthquake are the 1980 (Mw 7.2) and 2005 (Mw 7.2) earthquakes. I place orange lines approximately where the faults are that ruptured in 1980 and 2005. These are also plotted in the Rollins and Stein (2010) figure above. The Gorda plate is being deformed due to compression between the Pacific plate to the south and the Juan de Fuca plate to the north. Due to this north-south compression, the plate is deforming internally so that normal faults that formed at the spreading center (the Gorda Rise) are reactivated as left-lateral strike-slip faults. In 2014, there was another swarm of left-lateral earthquakes in the Gorda plate. I posted some material about the Gorda plate setting on this page.
Tectonic configuration of the Gorda deformation zone and locations and source models for 1976–2010 M ≥ 5.9 earthquakes. Letters designate chronological order of earthquakes (Table 1 and Appendix A). Plate motion vectors relative to the Pacific Plate (gray arrows in main diagram) are from Wilson [1989], with Cande and Kent’s [1995] timescale correction.
A: Mapped faults and fault-related ridges within Gorda plate based on basement structure and surface morphology, overlain on bathymetric contours (gray lines—250 m interval). Approximate boundaries of three structural segments are also shown. Black arrows indicated approximate location of possible northwest- trending large-scale folds. B, C: uninterpreted and interpreted enlargements of center of plate showing location of interpreted second-generation strike-slip faults and features that they appear to offset. OSC—overlapping spreading center.
Models of brittle deformation for Gorda plate overlain on magnetic anomalies modified from Raff and Mason (1961). Models A–F were proposed prior to collection and analysis of full-plate multibeam data. Deformation model of Gulick et al. (2001) is included in model A. Model G represents modification of Stoddard’s (1987) flexural-slip model proposed in this paper.
There are many different ways in which a landslide can be triggered. The first order relations behind slope failure (landslides) is that the “resisting” forces that are preventing slope failure (e.g. the strength of the bedrock or soil) are overcome by the “driving” forces that are pushing this land downwards (e.g. gravity). The ratio of resisting forces to driving forces is called the Factor of Safety (FOS). We can write this ratio like this: FOS = Resisting Force / Driving Force When FOS > 1, the slope is stable and when FOS < 1, the slope fails and we get a landslide. The illustration below shows these relations. Note how the slope angle α can take part in this ratio (the steeper the slope, the greater impact of the mass of the slope can contribute to driving forces). The real world is more complicated than the simplified illustration below. Landslide ground shaking can change the Factor of Safety in several ways that might increase the driving force or decrease the resisting force. Keefer (1984) studied a global data set of earthquake triggered landslides and found that larger earthquakes trigger larger and more numerous landslides across a larger area than do smaller earthquakes. Earthquakes can cause landslides because the seismic waves can cause the driving force to increase (the earthquake motions can “push” the land downwards), leading to a landslide. In addition, ground shaking can change the strength of these earth materials (a form of resisting force) with a process called liquefaction. Sediment or soil strength is based upon the ability for sediment particles to push against each other without moving. This is a combination of friction and the forces exerted between these particles. This is loosely what we call the “angle of internal friction.” Liquefaction is a process by which pore pressure increases cause water to push out against the sediment particles so that they are no longer touching. An analogy that some may be familiar with relates to a visit to the beach. When one is walking on the wet sand near the shoreline, the sand may hold the weight of our body generally pretty well. However, if we stop and vibrate our feet back and forth, this causes pore pressure to increase and we sink into the sand as the sand liquefies. Or, at least our feet sink into the sand. Below is a diagram showing how an increase in pore pressure can push against the sediment particles so that they are not touching any more. This allows the particles to move around and this is why our feet sink in the sand in the analogy above. This is also what changes the strength of earth materials such that a landslide can be triggered. Below is a diagram based upon a publication designed to educate the public about landslides and the processes that trigger them (USGS, 2004). Additional background information about landslide types can be found in Highland et al. (2008). There was a variety of landslide types that can be observed surrounding the earthquake region. So, this illustration can help people when they observing the landscape response to the earthquake whether they are using aerial imagery, photos in newspaper or website articles, or videos on social media. Will you be able to locate a landslide scarp or the toe of a landslide? This figure shows a rotational landslide, one where the land rotates along a curvilinear failure surface.
Source models for earthquakes S and T, 10 January 2010, M = 6.5, and 4 February 2010, Mw = 5.9.
Coulomb stress changes imparted by the 1980 Mw = 7.3 earthquake (B) to a matrix of faults representing the Mendocino Fault Zone, the Cascadia subduction zone, and NE striking left‐lateral faults in the Gorda zone. The Mendocino Fault Zone is represented by right‐lateral faults whose strike rotates from 285° in the east to 270° in the west; Cascadia is represented by reverse faults striking 350° and dipping 9°; faults in the Gorda zone are represented by vertical left‐lateral faults striking 45°. The boundary between the left‐lateral “zone” and the reverse “zone” in the fault matrix is placed at the 6 km depth contour on Cascadia, approximated by extending the top edge of the Oppenheimer et al.
Coulomb stress changes imparted by the Shao and Ji (2005) variable slip model for the 15 June 2005 Mw = 7.2 earthquake (P) to the epicenter of the 17 June 2005 Mw = 6.6 earthquake (Q). Calculation depth is 10 km.
Coulomb stress changes imparted by the D. Dreger (unpublished report, 2010, [no longer] available at http://seismo.berkeley.edu/∼dreger/jan10210_ff_summary.pdf) model for the January 2010 M = 6.5 shock (S) to nearby faults. East of the dashed line, stress changes are resolved on the Cascadia subduction zone, represented by a northward extension of the Oppenheimer et al. [1993] rupture plane for the 1992 Mw = 6.9 Cape Mendocino earthquake. West of the dashed line, stress changes are resolved on the NW striking nodal plane for the February 2010 Mw = 5.9 earthquake (T) at a depth of 23.6 km.
#EarthquakeReport for M 6.4 #Earthquake in Mendocino triple junction (Triangle of Doom) region early to tell (if we learned from last year) left or right lateral strike-slip prob in Gorda plate read more from last year's reporthttps://t.co/aS9ySr9YIPhttps://t.co/9HKHnpuwE9 pic.twitter.com/YZeimi6AC9 — Jason "Jay" R. Patton (@patton_cascadia) December 20, 2022 #EarthquakeReport for M 6.4 #Earthquake in Mendocino triple junction (Triangle of Doom) region aftershocks suggest left-lateral strike-slip in Gorda plate felt broadly, about 92%g in Ferndale read more from last year's reporthttps://t.co/aS9ySrs7WXhttps://t.co/9HKHnpMFSh pic.twitter.com/wt4UduAuvt — Jason "Jay" R. Patton (@patton_cascadia) December 20, 2022 #EarthquakeReport for M 6.4 #Earthquake offshore of #HumboldtCounty #California intensity summary: @USGS_Quakes model vs Did You Feel It? observations PGA in g units from https://t.co/KM7lTGSzX7 report forthcoming, 2021 review: https://t.co/aS9ySr9YIPhttps://t.co/9HKHnpuwE9 pic.twitter.com/K2JiOEKJTm — Jason "Jay" R. Patton (@patton_cascadia) December 22, 2022 #EarthquakeReport for M 6.4 #Earthquake in #Humboldt County #California interpretive poster showing aftershocks and comparison with '22 sequence no foreshocks@USGS_Quakes slip/GNSS model compared with GNSS observations report forthcoming, '22 report: https://t.co/aS9ySr9YIP pic.twitter.com/NfYkUuW13J — Jason "Jay" R. Patton (@patton_cascadia) December 22, 2022 #EarthquakeReport for M6.4 #Earthquake offshore northern #California#FerndaleEarthquake hypocenters from @USGS_Quakes read report herehttps://t.co/0rRNL3TfNk pic.twitter.com/Mni4dbD8Oo — Jason "Jay" R. Patton (@patton_cascadia) December 24, 2022 #EarthquakeReport for M6.4 #Earthquake in #HumboldtCounty #California Gorda intraplate left-lateral strike-slip earthquake some tensional mechanisms possibly 2 main faults involved (?) outlined in white read report herehttps://t.co/0rRNL3TfNk pic.twitter.com/FQripjzAa0 — Jason "Jay" R. Patton (@patton_cascadia) December 26, 2022 #EarthquakeReport for M 6.4 #Earthquake in northern @California updated plot: hypocenters compared to Gorda crust and the @USGS_Quakes Finite Fault Model showing that most of the slip occurred in the NAP (not sure this is correct) read more herehttps://t.co/0rRNL3TfNk pic.twitter.com/Nca4IimQ3z — Jason "Jay" R. Patton (@patton_cascadia) December 26, 2022 #EarthquakeReport for M6.4 #Earthquake in northern #California geology from CDMG '99 and McLaughlin et al. '00. units are labeled, so no legend (abt 30 units in each data set) lack of upper plate structures oriented with 6.4 seismicity read report here:https://t.co/0rRNL3TfNk pic.twitter.com/iyCQBCsxf4 — Jason "Jay" R. Patton (@patton_cascadia) December 26, 2022 a triple junction is defined as where three plate boundaries meet, not where three plates meet (though that is also true). the types of triple junctions (e.g., RRR, TTT, RFF) refer to the types of faults that meet there. https://t.co/zfP2DidN6Ihttps://t.co/CLUfzwNanj pic.twitter.com/t9O5RFstfY — Jason "Jay" R. Patton (@patton_cascadia) December 30, 2022 #EarthquakeReport for M6.4 & 5.4 #Earthquakes in the #Triangleofdoom #Mendocinotriplejunction M6.4 – left-lateral strike-slip (in crust?) updated aftershock map and hypocenter profile read the report herehttps://t.co/0rRNL3TfNk pic.twitter.com/HNpiZRBP8a — Jason "Jay" R. Patton (@patton_cascadia) January 3, 2023 The #earthquake stopped campus clocks at 2:34 AM. pic.twitter.com/PeQNwvL4I0 — Cal Poly Humboldt (@humboldtcalpoly) December 22, 2022 Good morning Redwood Coast CA. Did you feel the magnitude 6.4 quake about 7.5 miles southwest of Ferndale at 2:34 am? The #ShakeAlert system was activated. See: https://t.co/zwOapjTWaA pic.twitter.com/eMSUAT3inw — USGS ShakeAlert (@USGS_ShakeAlert) December 20, 2022 A M6.4 earthquake has occurred south of Eureka, CA in northern CA (Humboldt Co.). Additional shaking from aftershocks is expected in the region. We are continuing to monitor this event, so check back for additional information. #Humboldt #earthquake pic.twitter.com/DpaIlz3RGV — California Geological Survey (@CAGeoSurvey) December 20, 2022 A M6.4 earthquake & several aftershocks hit the coast near Ferndale, CA. Epicenter is close enough to land that strong shaking & some ground/structure damage is expected. #earthquake #Humboldt pic.twitter.com/YcO3mVEJCI — Brian Olson (@mrbrianolson) December 20, 2022 #EarthquakeReport for M 6.4 #Earthquake in Mendocino triple junction (Triangle of Doom) region felt broadly at least intensity MMI 8 read more from last year's reporthttps://t.co/aS9ySr9YIPhttps://t.co/9HKHnpuwE9 pic.twitter.com/8qAaSK6i9y — Jason "Jay" R. Patton (@patton_cascadia) December 20, 2022 #EarthquakeReport for M 6.4 #Earthquake in Mendocino triple junction (Triangle of Doom) region modest chance for eq triggred landslides read more from last year's reporthttps://t.co/aS9ySr9YIPhttps://t.co/RXs6q07wjX pic.twitter.com/zI9cPfnRUG — Jason "Jay" R. Patton (@patton_cascadia) December 20, 2022 A few more clean signals pic.twitter.com/53tL2Rixkb — Brendan Crowell (@bwcphd) December 20, 2022 That was a big one. Power is now out in #ferndaleca. House is a mess. #earthquake pic.twitter.com/YEmcv1Urhp — Caroline Titus (@caroline95536) December 20, 2022 About 50,000 PG&E customers are without power in Humboldt after that earthquake, which was a preliminary magnitude 6.4.https://t.co/TLWiUpfEGp — North Coast Journal (@ncj_of_humboldt) December 20, 2022 Road Closure: State Route 211 at Fernbridge, Humboldt County is CLOSED. The bridge is closed while we conduct safety inspections due to possible seismic damage. pic.twitter.com/601oOQRz2o — Caltrans District 1 (@CaltransDist1) December 20, 2022 FERNBRIDGE EARTHQUAKE DAMAGE: Damage to Fernbridge following the 6.2 magnitude #earthquake in Humboldt County. Main road to Ferndale currently closed off by CalTrans as crews inspect for additional damage. pic.twitter.com/4BPOSvZrN9 — Austin Castro (@AustinCastroTV) December 20, 2022 Auto solution FMNEAR (Géoazur/OCA) with regional records for the M 6.3 – OFFSHORE NORTHERN CALIFORNIA – 2022-12-20 10:34:25 UTC (Loc EMSC used to trigger inversion).https://t.co/UHDsc1hVXA — Bertrand Delouis (@BertrandDelouis) December 20, 2022 Mw=6.4, NEAR COAST OF NORTHERN CALIF. (Depth: 9 km), 2022/12/20 10:34:25 UTC – Full details here: https://t.co/nC4QZqppm0 pic.twitter.com/QW0ggaT4dE — Earthquakes (@geoscope_ipgp) December 20, 2022 strong #Earthquake offshore California, United States Of America — CATnews (@CATnewsDE) December 20, 2022 The area where this quake occurred is quite active. These images from @EarthScope_sci IRIS Earthquake Browser show earthquakes in the area of M4+, M5+, M6+ and M7+. pic.twitter.com/y3xafBrCfd — Wendy Bohon, PhD 🌏 (@DrWendyRocks) December 20, 2022 In fact, there have already been 20+ aftershocks of M2.5+! Again, this is normal and expected. PSA: aftershocks are just smaller earthquakes that occur after a larger quake. Here’s more info https://t.co/byWunrqSqZ — Wendy Bohon, PhD 🌏 (@DrWendyRocks) December 20, 2022 — Robert Martin (@NordBob) December 20, 2022 Following the M6.4 mainshock, there have been well over 20 recorded aftershocks above M2.5. pic.twitter.com/Gej6rRNDlG — EarthScope Consortium (@EarthScope_sci) December 20, 2022 Saw this on Facebook from someone in Eureka after tonight's quake. A reminder to "Secure Your Space" by tethering heavy furniture to the wall for this exact reason. #earthquake pic.twitter.com/1CiYbLOQcE — Brian Olson (@mrbrianolson) December 20, 2022 Some people in Los Angeles and Tacoma really need to chill out and have less caffeine before bed 🧐🤔 https://t.co/5zIRhUR6eq pic.twitter.com/iURHlVVuOS — Austin Elliott (@TTremblingEarth) December 20, 2022 Just took a cruise down Main Street #ferndaleca. Couldn’t see one broken window. Many store owners replaced broken ones after 6.2 on this same day in 2021. Also today’s #earthquake shook north/south. #earthquakeca pic.twitter.com/Ua1nMx0UuJ — Caroline Titus (@caroline95536) December 20, 2022 Ferndale M6.4 strike-slip earthquake and aftershocks so far, all lining up along the left-lateral nodal plane of the focal mechanism. pic.twitter.com/lfWX5Qz4FF — Harold Tobin (@Harold_Tobin) December 20, 2022 M6.4 #earthquake near Ferndale, CA: Seismicity for today (red), the past year (orange) and back to 1982 (green-blue-purple). Views from above/south/east. Today's events may be in upper part of down-going, Gorda plate. pic.twitter.com/WdvPq85LJP — Anthony Lomax 😷🇪🇺🌍🇺🇦 (@ALomaxNet) December 20, 2022 Cal OES is coordinating with local and tribal governments to assess the impacts of the Earthquake and supporting with resources, mutual aid and damage assessment. State Agency response including Cal OES, Cal Fire, Cal Trans, Cal CGS, CHP in support of local efforts — California Governor's Office of Emergency Services (@Cal_OES) December 20, 2022 Peak ground acceleration plot of seismic stations that recorded shaking from last night's M6.4 earthquake in Humboldt County. Notably, several values are *WELL* above the predicted envelope given distance from the epicenter. Is this real? Any explanations? Near-field effect? pic.twitter.com/QHdAMlglbM — Brian Olson (@mrbrianolson) December 20, 2022 A brief explainer about the M6.4 earthquake near Ferndale in Northern California pic.twitter.com/3Ar03QFlC3 — Wendy Bohon, PhD 🌏 (@DrWendyRocks) December 20, 2022 Gov. Newsom & State officials provide updates on the M6.4 earthquake today near Ferndale in Humboldt County. #earthquake #Eureka @Cal_OES @GovPressOffice https://t.co/xHAkna9UYw — California Geological Survey (@CAGeoSurvey) December 20, 2022 Cindy Pridmore representing CGS at today's press conference on the M6.4 Ferndale earthquake. She noted quakes of this size aren't uncommon here & people should be aware of continuing aftershocks, especially if they are in structures already damaged by the quake. @CAGeoSurvey pic.twitter.com/hRrJkLT7Tz — Brian Olson (@mrbrianolson) December 20, 2022 Small teams of CGS geologists are currently out in the Ferndale, Rio Dell, & Eureka areas documenting structural & ground damage from this morning's M6.4 earthquake. Seeing where damage occurs helps us understand how shaking intensity & damage are related. #earthquake #humboldt — California Geological Survey (@CAGeoSurvey) December 20, 2022 The @USGS_Quakes aftershock forecast for the M6.4 event in Northern California is out. MOST LIKELY – “There will likely be smaller aftershocks within the next week with up to 24 M3+ aftershocks. M3+ aftershocks are large enough to be felt nearby.” https://t.co/7o2iJhozp0 — Wendy Bohon, PhD 🌏 (@DrWendyRocks) December 20, 2022 Important info for folks that live in Earthquake country 👇🏻 https://t.co/ZGWNf1zYpr — Wendy Bohon, PhD 🌏 (@DrWendyRocks) December 20, 2022 Sadly, two reported deaths. — Jason "Jay" R. Patton (@patton_cascadia) December 20, 2022 This Magnitude 6.4 earthquake in California and subsequent power outage got me wanting to share this new video guide on small scale solar back up now. This is the short version of the video based on this step-by-step guide – https://t.co/af5okVx2P7#photovoltaics #prepper pic.twitter.com/oxmYbiNQ9i — Lonny Grafman (@LonnyGrafman) December 20, 2022 Seismicity map of today's Ferndale earthquakes with red outline (suggesting EW plane may be fault), and the events from exactly a year ago in purple. A bit confusing, since the M6.2 from a year ago appears to have been relocated significantly from its original offshore location. pic.twitter.com/K3HvECUt4l — Jascha Polet (@CPPGeophysics) December 20, 2022 Still not seeing many images of damage, but based on anecdotes from folks in quake zone it does sound like there was damage to some structures & especially to infrastructure. I suspect that ongoing widespread regional power outages are reason we haven't heard more yet.#earthquake https://t.co/ACvlDpvqJR pic.twitter.com/ejHBRaMOHJ — Daniel Swain (@Weather_West) December 20, 2022 Before (May 2018) & After (today) photos of the old Humboldt Creamery building in Loleta (across from the Cheese Factory). Old brick buildings perform so badly during earthquakes. I hope the cheese factory is safe.🧀🥛 #FerndaleEarthquake #earthquake pic.twitter.com/aMbbpsrsz6 — Brian Olson (@mrbrianolson) December 20, 2022 Some excellent 5-Hz GNSS velocities for the Ferndale EQ showing some strong site amplification at @EarthScope_sci site P168 (peak 35 cm/s). Closest seismic site KNEE is in good agreement. pic.twitter.com/OSskpMEMjX — Brendan Crowell (@bwcphd) December 21, 2022 Wow! Extreme ground accelerations, well above 1 g, during the recent M6.4 earthquake near Ferndale, Caifornia, recorded in Rio Dell: https://t.co/HmJa5feZ3g — Pablo Ampuero (@DocTerremoto) December 20, 2022 Governor @GavinNewsom proclaimed a state of emergency for Humboldt County to support the emergency response to today’s 6.4 magnitude earthquake near the City of Ferndale. https://t.co/EieUtBovqT — Office of the Governor of California (@CAgovernor) December 21, 2022 'Significant' Damages in Rio Dell Area, Says Humboldt Office of Emergency Services; 11 Injuries, Two Dead from Medical Emergencies https://t.co/ruNr3ma5tN — Lost Coast Outpost (@LCOutpost) December 20, 2022 Road damage from Northern California earthquake, in Rio Dell pic.twitter.com/P9eSSX4kRU — EthanBaron (@ethanbaron) December 21, 2022 Over 3 million people in California & Oregon received #ShakeAlert-powered alerts during today’s M6.4 quake near Ferndale, CA. #ShakeAlert is success because of: @Cal_OES @OregonOEM @waEMD @waDNR @CAGeoSurvey @OregonGeology @OHAZ_UO @UW @PNSN1 @CaltechSeismo @BerkeleySeismo @USGS pic.twitter.com/wWL4N6aMxI — USGS ShakeAlert (@USGS_ShakeAlert) December 20, 2022 Watching observations from this morning’s #earthquake come in: Some from our @CAGeoSurvey geologists and others gleaned from news reports and social media by our GIS professionals. Most of these are damage reports so far. Incredibly valuable spatial data! pic.twitter.com/JUPIV2AAtR — Tim Dawson (@timblor) December 20, 2022 Real-time GNSS displacements recorded by GSeisRT for the Ferndale M6.4 event on Dec. 20th. @EarthScope_sci pic.twitter.com/HZz6F758l5 — Jianghui Geng (@GengJianghui) December 21, 2022 Our field teams were out documenting structural & ground damage yesterday to help us understand the shaking effects from yesterday's M6.4 Ferndale earthquake. — California Geological Survey (@CAGeoSurvey) December 21, 2022 Learn more about the M6.4 earthquake near Ferndale, CA in this @USGS featured story : https://t.co/T5EYMvlKK5 @USGS_Quakes @CAGeoSurvey @Cal_OES @OregonOEM @OHAZ_UO @PNSN1 @waDNR @waShakeOut @ShakeOut @ECA @CalConservation @CaltechSeismo @BerkeleySeismo @ListosCA @FEMARegion9 pic.twitter.com/mgPPGQeM54 — USGS ShakeAlert (@USGS_ShakeAlert) December 21, 2022 Regarding the North Coast earthquake, my undergrad Geography advisor, Eugenie Rovai (Rio Dell local), did social geography research after the 1994 earthquake, and wrote about how history affected the capacity for each community to recover. https://t.co/eY4LXrGekl pic.twitter.com/HuWTkzyjVJ — Zeke Lunder ~ The Lookout (@wildland_zko) December 22, 2022 The earthquake waves from the M6.4 Ferndale quake were recorded by seismic stations across North America. By the time the waves move away from the region where the earthquake occurred they are much too small to feel but not too small to measure. pic.twitter.com/s7UYGUjPey — Wendy Bohon, PhD 🌏 (@DrWendyRocks) December 22, 2022 The supercomputer has finished chugging. Here is a preliminary simulation of how yesterday’s M6.4 earthquake might have focused shaking in specific areas. Event page here: https://t.co/UA9LAh0bJ2 pic.twitter.com/bdR9ZFYapn — USGS Earthquakes (@USGS_Quakes) December 21, 2022 What’s the difference between geologic hazard and risk? What are the USGS National Seismic Hazard Maps, and how are they used? Find out in this introduction to the National Seismic Hazard Maps: https://t.co/biDoY1ewWx#SeismicHazards #Earthquakes pic.twitter.com/T48ytJ7gKJ — USGS (@USGS) December 22, 2022 CA worked night and day and — less than 48 hours after a strong earthquake in Humboldt County — power has been restored to all communities. Thank you @Cal_OES, @CaltransHQ, @CAL_FIRE, @CA_EMSA, and @CHP_HQ for helping recovery efforts.https://t.co/JIaFUWJO9A — Office of the Governor of California (@CAgovernor) December 23, 2022 And the corresponding map view. High-precision relocations of M≥2 1982 to 2021/12 done with NLL-SSST-coherence (https://t.co/EwE8DRzwvU), past year done with NLL-SSST. Earthquake arrival data from https://t.co/7TWxvNHnee pic.twitter.com/KVN606rFfC — Anthony Lomax 😷🇪🇺🌍🇺🇦 (@ALomaxNet) December 22, 2022 The 12/20/22 M6.4 earthquake has produced a nice aftershock sequence that illuminates the fault that likely ruptured. A nice zone northeast of the epicenter. @CAGeoSurvey found no surface rupture, so this is a seismologist’s earthquake with lots to learn. pic.twitter.com/XJB8MuJPno — Tim Dawson (@timblor) December 24, 2022 ARIA has processed interferograms with 23 December Copernicus Sentinel-1 covering M6.4 Ferndale earthquake. Geocoded UNWrapped (GUNW) interf. files available from NASA ASF archive. @iamgracebato did InSAR time-series with MintPy to mitigate atmosphere in attached map. pic.twitter.com/6zqOpGFzD0 — Advanced Rapid Imaging & Analysis (ARIA) (@aria_hazards) December 24, 2022 HUMBOLDT OES: Around 70 Local Buildings Deemed Unsafe in the Wake of the Quakes, in Total; Here is the Big List of Resources for People Who Need Help https://t.co/yTizDPCnE5 — Lost Coast Outpost (@LCOutpost) January 3, 2023
While I was travelling back from a USGS Powell Center Workshop on the recurrence of earthquakes along the Cascadia subduction zone, there was an earthquake (gempa) offshore of Sumatra. https://earthquake.usgs.gov/earthquakes/eventpage/us7000iqpn/executive There was actually a foreshock (more than one): https://earthquake.usgs.gov/earthquakes/eventpage/us7000iq2d/executive OK, sunset led to nap, led to bed. The plate boundary offshore of Sumatra, Indonesia, is a convergent (moving together) plate boundary. Here, the Australia plate subducts northwards beneath the Sunda plate (part of the Eurasia plate) along a megathrust subduction zone fault. This subduction forms a deep sea trench, the Sunda trench. This was a shallow event near the trench formed by the subduction here. The magnitude was a little small for generating a large tsunami. However, it was shallow, so the deformation reached the sea floor and generated tsunami recorded on several tide gages in the region. These gages are operated by the Indonesian Geospatial Reference System, though there are some gages that are posted on the European Union World Sea Levels website. The water surface elevation data was a little noisy on these tide gage plots, but two of them had sufficient signal to justify my interpretation that these are tsunami. My interpretations could be incorrect and I include two plots below. Many are familiar with the Boxing Day Earthquake and Tsunami from December 2004. This is one of the most deadly events in modern history, almost a quarter million people perished (mostly from the tsunami). These lives lost did lead to changes in how tsunami risk is managed worldwide. So, these lives lost were not lost in vain (though it would be better if they were not lost, we can all agree to that). The southern Sumatra subduction zone has an excellent record of prehistoric and historic earthquakes. For example, there is a couplet where earthquake slips overlapped slightly, the 1797 and 1833 earthquakes. Many think that this area is the next place a large tsunamigenic earthquake may occur. Below we can see the analysis from Chlieh et al. (2008) where they suggest that there is considerable tectonic strain accumulated since these 1797 and 1833 earthquakes. There have been several large earthquakes in this area but they may not have released this strain. If we look at the Chlieh et al. (2008) study, we will notice that this M 6.9 earthquake happened in an area thought to be in an area that is not accumulating much tectonic strain. I post a figure showing this later in the report. There are millions of people who live in the coastal lowlands of Padang who may have difficulty evacuating in time should an earthquake like the 2004 Sumatra-Andaman subduction zone earthquake were to occur in this area. For those that live along the coast here, the ground shaking from the earthquake is their natural notification to evacuate to high ground. For those that live across the ocean, they will get warning notifications to help them learn to evacuate since they won’t have the ground shaking as a warning. This is what happened to many people in December 2004 along the east coast of India and along the coast of Sri Lanka. Here are some of the larger historic earthquakes in this area, ordered by magnitude:
Sumatra core location and plate setting map with sedimentary and erosive systems figure. A. India-Australia plate subducts northeastwardly beneath the Sunda plate (part of Eurasia) at modern rates (GPS velocities are based on regional modeling of Bock et al, 2003 as plotted in Subarya et al., 2006). Historic earthquake ruptures (Bilham, 2005; Malik et al., 2011) are plotted in orange. 2004 earthquake and 2005 earthquake 5 meter slip contours are plotted in orange and green respectively (Chlieh et al., 2007, 2008). Bengal and Nicobar fans cover structures of the India-Australia plate in the northern part of the map. RR0705 cores are plotted as light blue. SRTM bathymetry and topography is in shaded relief and colored vs. depth/elevation (Smith and Sandwell, 1997). B. Schematic illustration of geomorphic elements of subduction zone trench and slope sedimentary settings. Submarine channels, submarine canyons, dune fields and sediment waves, abyssal plain, trench axis, plunge pool, apron fans, and apron fan channels are labeled here. Modified from Patton et al. (2013 a).
Map of Southeast Asia showing recent and selected historical ruptures of the Sunda megathrust. Black lines with sense of motion are major plate-bounding faults, and gray lines are seafloor fracture zones. Motions of Australian and Indian plates relative to Sunda plate are from the MORVEL-1 global model [DeMets et al., 2010]. The fore-arc sliver between the Sunda megathrust and the strike-slip Sumatran Fault becomes the Burma microplate farther north, but this long, thin strip of crust does not necessarily all behave as a rigid block. Sim = Simeulue, Ni = Nias, Bt = Batu Islands, and Eng = Enggano. Brown rectangle centered at 2°S, 99°E delineates the area of Figure 3, highlighting the Mentawai Islands. Figure adapted from Meltzner et al. [2012] with rupture areas and magnitudes from Briggs et al. [2006], Konca et al. [2008], Meltzner et al. [2010], Hill et al. [2012], and references therein.
Recent and ancient ruptures along the Mentawai section of the Sunda megathrust. Colored patches are surface projections of 1-m slip contours of the deep megathrust ruptures on 12–13 September 2007 (pink to red) and the shallow rupture on 25 October 2010 (green). Dashed rectangles indicate roughly the sections that ruptured in 1797 and 1833. Ancient ruptures are adapted from Natawidjaja et al. [2006] and recent ones come from Konca et al. [2008] and Hill et al. (submitted manuscript, 2012). Labeled points indicate coral study sites Sikici (SKC), Pasapuat (PSP), Simanganya (SMY), Pulau Pasir (PSR), and Bulasat (BLS).
Distribution of coupling on the Sumatra megathrust derived from the formal inversion of the coral and of the GPS data (Tables 2, 3, and 4) prior to the 2004 Sumatra-Andaman earthquake (model I-a in Table 7). (a) Distribution of coupling on the megathrust. Fully coupled areas are red, and fully creeping areas are white. Three strongly coupled patches are revealed beneath Nias island, Siberut island, and Pagai island. The annual moment deficit rate corresponding to that model is 4.0 X 10^20 N m/a. (b) Observed (black vectors) and predicted (red vectors) horizontal velocities appear. Observed and predicted vertical displacements are shown by color-coded large and small circles, respectively. The Xr^2 of this model is 3.9 (Table 7).
Distribution of coupling on the Sumatra megathrust derived from the formal inversion of the horizontal velocities and uplift rates derived from the CGPS measurements at the SuGAr stations (processed at SOPAC). To reduce the influence of postseismic deformation caused by the March 2005 Nias-Simeulue rupture, velocities were determined for the period between June 2005 and October 2006. (a) Distribution of coupling on the megathrust. Fully coupled areas are red and fully creeping areas are white. This model reveals strong coupling beneath the Mentawai Islands (Siberut, Sipora, and Pagai islands), offshore Padang city, and suggests that the megathrust south of Bengkulu city is creeping at the plate velocity. (b) Comparison of observed (green) and predicted (red) velocities. The Xr^2 associated to that model is 24.5 (Table 8).
Distribution of coupling on the Sumatra megathrust derived from the formal inversion of all the data (model J-a, Table 8). (a) Distribution of coupling on the megathrust. Fully coupled areas are red, and fully creeping areas are white. This model shows strong coupling beneath Nias island and beneath the Mentawai (Siberut, Sipora and Pagai) islands. The rate of accumulation of moment deficit is 4.5 X 10^20 N m/a. (b) Comparison of observed (black arrows for pre-2004 Sumatra-Andaman earthquake and green arrows for post-2005 Nias earthquake) and predicted velocities (in red). Observed and predicted vertical displacements are shown by color-coded large and small circles (for the corals) and large and small diamonds (for the CGPS), respectively. The Xr^2 of this model is 12.8.
Comparison of interseismic coupling along the megathrust with the rupture areas of the great 1797, 1833, and 2005 earthquakes. The southernmost rupture area of the 2004 Sumatra-Andaman earthquake lies north of our study area and is shown only for reference. Epicenters of the 2007 Mw 8.4 and Mw 7.9 earthquakes are also shown for reference. (a) Geometry of the locked fault zone corresponding to forward model F-f (Figure 6c). Below the Batu Islands, where coupling occurs in a narrow band, the largest earthquake for the past 260 years has been a Mw 7.7 in 1935 [Natawidjaja et al., 2004; Rivera et al., 2002]. The wide zones of coupling, beneath Nias, Siberut, and Pagai islands, coincide well with the source of great earthquakes (Mw > 8.5) in 2005 from Konca et al. [2007] and in 1797 and 1833 from Natawidjaja et al. [2006]. The narrow locked patch beneath the Batu islands lies above the subducting fossil Investigator Fracture Zone. (b) Distribution of interseismic coupling corresponding to inverse model J-a (Figure 10). The coincidence of the high coupling area (orange-red dots) with the region of high coseismic slip during the 2005 Nias-Simeulue earthquake suggests that strongly coupled patches during interseismic correspond to seismic asperities during megathrust ruptures. The source regions of the 1797 and 1833 ruptures also correlate well with patches that are highly coupled beneath Siberut, Sipora, and Pagai islands.
Latitudinal distributions of seismic moment released by great historical earthquakes and of accumulated deficit of moment due to interseismic locking of the plate interface. Values represent integrals over half a degree of latitude. Accumulated interseismic deficits since 1797, 1833, and 1861 are based on (a) model F-f and (b) model J-a. Seismic moments for the 1797 and 1833 Mentawai earthquakes are estimated based on the work by Natawidjaja et al. [2006], the 2005 Nias-Simeulue earthquake is taken from Konca et al. [2007], and the 2004 Sumatra-Andaman earthquake is taken from Chlieh et al. [2007]. Postseismic moments released in the month that follows the 2004 earthquake and in the 11 months that follows the Nias-Simeulue 2005 earthquake are shown in red and green, respectively, based on the work by Chlieh et al. [2007] and Hsu et al. [2006].
Free-air gravity anomaly map derived from satellite altimetry [Sandwell and Smith, 2009] over the Wharton Basin area.
Structure and age of the Wharton Basin deduced from free-air gravity anomaly [Sandwell and Smith, 2009; background colors] for the fracture zones (thin black longitudinal lines), and marine magnetic anomaly profiles (not shown) for the isochrons (thin black latitudinal lines). The plain colors represent the oceanic lithosphere created during normal geomagnetic polarity intervals (see legend for the ages of Chrons 20 to 34 according to the time scale of Gradstein et al. [2004]). Compartments separated by major fracture zones are labeled A to H. Grey areas: oceanic plateaus, thick black line: Sunda Trench subduction zone.
Reconstitution of the subducted magnetic isochrons and fracture zones of the northern Wharton Basin using the finite rotation parameters deduced from our two- and three-plate reconstructions. (a) First the geometry is restored on the Earth surface, then (b) it is draped on the top of the subducting plate as derived from seismic tomography [Pesicek et al., 2010] shown by the thin dotted lines at intervals of 100 km (b). Colored dots: identified magnetic anomalies; colored triangles: rotated magnetic anomalies, solid lines; observed fracture zones and isochrons, dashed lines: uncertain or reconstructed fracture zones, dotted lines: reconstructed isochrons from rotated magnetic anomalies (two-plate and three-plate reconstructions), colored area: oceanic lithosphere created during normal geomagnetic polarity intervals (see legend for the ages; the colored areas without solid or dotted lines have been interpolated), grey areas: oceanic plateaus, thick line: Sunda Trench subduction zone.
The deviation of the Sunda Trench from a regular arc shape (dotted lines) off Sumatra is explained by the presence of the younger, hotter and therefore lighter lithosphere in compartments C–F, which resists subduction and form an indentor (solid line). The very young compartment G was probably part of this indentor before oceanic crust formed at slow spreading rate near the Wharton fossil spreading center approached subduction: The weaker rheology of outcropping or shallow serpentinite may have favored the restoration of the accretionary prism in this area. Further south, the deviation off Java is explained by the resistance of the thicker Roo Rise, an oceanic plateau entering the subduction.
Annual probability of experiencing a tsunami with a height at the coast of (a) 0.5m (a tsunami warning) and (b) 3m (a major tsunami warning).
EarthquakeReport for M6.9 #Gempa #Earthquake offshore of #Sumatra #Indonesia Appears to be on the megathrust subduction zone fault Read more about the regional tectonics herehttps://t.co/sjXP2RmtVuhttps://t.co/bglPVLQUDt pic.twitter.com/KSdUDVh9HD — Jason "Jay" R. Patton (@patton_cascadia) November 18, 2022 #EarthquakeReport for M 6.9 #Gempa #Earthquake offshore of #Sumatra #Indonesia appears to be a megathrust subduction zone fault earthquake generated a small tsunami recorded on tide gages read more here:https://t.co/KKizpqJuSa pic.twitter.com/W4gCCJ9bKY — Jason "Jay" R. Patton (@patton_cascadia) November 20, 2022 #EarthquakeReport for M 6.9 #Gempa #Earthquake offshore of #Sumatra #Indonesia probably slip along megathrust subduction zone where Chlieh modeled low seismogenic coupling https://t.co/nuGY5m9iGD *in area absent of GPS/microatoll data read more here:https://t.co/KKizpqsrQa pic.twitter.com/oZP5u7JgiK — Jason "Jay" R. Patton (@patton_cascadia) November 20, 2022 #EarthquakeReport #TsunamiReport for M 6.9 #Gempa #Earthquake offshore of #Sumatra #Indonesia Cocos Isle gage updated due to twitter peer review from @Harold_Tobin thanks! also added Bintuhan record interp poster and plots updated in report herehttps://t.co/KKizpqsrQa pic.twitter.com/TGgCZeA1MV — Jason "Jay" R. Patton (@patton_cascadia) November 20, 2022 Effects of the magnitude 6.9 #earthquake off #Sumatra #Indonesia was felt in my apartment over 776 km away in #Singapore. Managed to record this lamp swaying. #gempa #seismology #sismo #terremoto #geology pic.twitter.com/b1CdcxrCLm — GeoGeorge (@GeoGeorgeology) November 18, 2022 Preliminary M6.9 #Earthquake – Learn more about us at https://t.co/ojzht2DDAL – EVENT: https://t.co/WbAhjnStUl pic.twitter.com/W5SOXtMdjn — Raspberry Shake Earthquake Channel (@raspishakEQ) November 18, 2022 I love this figure by Kyle Bradley – really highlights the Mentawai Seismic Gap, a region at high risk of a large tsunamigenic earthquake offshore Sumatra. https://t.co/DJ1MSuKGVa pic.twitter.com/j8A0LjReNO — Dr. Judith Hubbard (@JudithGeology) March 18, 2022 No #tsunami threat to Australia from magnitude 6.8 #earthquake near Southwest of Sumatra, Indonesia. Latest advice at https://t.co/Tynv3Zygqi. pic.twitter.com/ISugUTXpVm — Bureau of Meteorology, Australia (@BOM_au) November 18, 2022 NO TSUNAMI THREAT! An earthquake occurred in South Sumatra region with following preliminary parameters 👇🏼 There is no tsunami threat to SL at present & coastal areas of SL are declared safe.#Tsunami #NoThreat #SriLanka #LKA pic.twitter.com/CPQMp12dqD — Department of Meteorology Sri Lanka (@SLMetDept) November 18, 2022 Earthquakes commonly occur near Sumatra, as the Indo-Australian Plate subducts under the Sunda Plate. The M6.9 earthquake occurred at a depth of 25 km, likely on the subduction interface.https://t.co/OM7bvJsmTO pic.twitter.com/NS3rGVd8hR — EarthScope Consortium (@EarthScope_sci) November 18, 2022 Surface waves from a M6.9 earthquake near Bengkulu, Indonesia at 18/11/2022 13:37:09UTC, received in the UK approximately an hour after the earthquake on @BGS and @raspishake devices. The frequency of these waves is shown on a plot from the BGS Elmsett seismometer. @rdlarter pic.twitter.com/OQkXOm5K1o — Mark Vanstone (@wmvanstone) November 19, 2022 Waves from the M6.9 earthquake southwest of Sumatra shown on a nearby station using Station Monitor. https://t.co/Tir0KZmCJF pic.twitter.com/H5AjBzaKRH — EarthScope Consortium (@EarthScope_sci) November 18, 2022 Location and First-motion mechanism: Mwp6.8 #earthquake Southwest of Sumatra, Indonesia https://t.co/kCIw9Vypa6 https://t.co/xebYrDiQ5S pic.twitter.com/May21uExD6 — Anthony Lomax 😷🇪🇺🌍🇺🇦 (@ALomaxNet) November 18, 2022 Watch the waves from the M6.9 earthquake in Sumatra, Indonesia roll across seismic stations in North America. (THREAD 🧵) pic.twitter.com/JMolvkAy4b — EarthScope Consortium (@EarthScope_sci) November 18, 2022 Global surface and body wave sections from the M6.9 earthquake southwest of Sumatra, Indonesiahttps://t.co/a0ciLbpC9x pic.twitter.com/T4HDlrwvjy — EarthScope Consortium (@EarthScope_sci) November 18, 2022 Back projection for the M6.9 earthquake southwest of Sumatra, Indonesiahttps://t.co/SLKRaU3oUA pic.twitter.com/glLYRXLj7X — EarthScope Consortium (@EarthScope_sci) November 18, 2022 Earthquakes commonly occur near Sumatra, as the Indo-Australian Plate subducts under the Sunda Plate. The M6.9 earthquake occurred at a depth of 25 km, likely on the subduction interface.https://t.co/OM7bvJsmTO pic.twitter.com/NS3rGVd8hR — EarthScope Consortium (@EarthScope_sci) November 18, 2022 Mw=6.9, SOUTHWEST OF SUMATRA, INDONESIA (Depth: 19 km), 2022/11/18 13:37:06 UTC – Full details here: https://t.co/uLuj3Ztf0a pic.twitter.com/3V9bk1wFaq — Earthquakes (@geoscope_ipgp) November 18, 2022 Preliminary M6.9 #Earthquake – Learn more about us at https://t.co/ojzht2DDAL – EVENT: https://t.co/WbAhjnStUl pic.twitter.com/W5SOXtMdjn — Raspberry Shake Earthquake Channel (@raspishakEQ) November 18, 2022
Early this morning I received some notifications of earthquakes along the Tonga trench (southwestern central Pacific Ocean). It was about 2am my local time. I work on the tsunami program for the California state tsunami program (CTP) and we respond to tsunami to (1) help local communities do their first response activities so that they can help reduce suffering and to (2) document the impact of these tsunami. Because of this work, our team is “at the ready” 24 hours a day, 7 days a week, to respond to these events. Luckily, this event was unlikely to generate a tsunami that would impact California. I went back to sleep. This morning I put together a report and checked to see if there was a tsunami generated. Here is one place that I check for tsunami records as observed on tide gages http://www.ioc-sealevelmonitoring.org/map.php. I did not see anything convincing. This earthquake, from last night my time, has a magnitude of M 7.3. https://earthquake.usgs.gov/earthquakes/eventpage/us7000ip0l/executive This area of the Earth has a plate boundary fault system called a subduction zone. A subduction zone is a convergent plate boundary, which means that the plates on either side of the boundary move towards each other. Here, the Pacific plate dives westwards beneath the Australia plate, forming the Tonga trench. Below is a schematic illustration showing what these plates may look like if we cut into the Earth and viewed this subduction zone from the side. Note the Pacific plate on the right and the Australia plate on the left, with the megathrust subduction zone fault where they meet. This illustration shows where earthquakes may happen along this plate boundary. There could be interface earthquakes along the megathrust fault (megathrust earthquakes). These are what most people are familiar with when they are thinking about tsunami (e.g., the 2011 Great East Japan Earthquake and Tsunami). In the upper plate (the Australia plate), there can be crustal fault earthquakes. In the lower plate (the Pacific plate) there can be slab earthquakes (events within the crust, aka the slab), and there can be outer rise earthquakes). The outer rise is a part of the plate that is warping up and down because of the forces adjacent to the subduction zone. This warping can cause extension in the upper part, and compression in the lower part, of this plate. This 11 Nov 2022 M 7.3 earthquake was a compressional (reverse) earthquake in the outer rise region of this plate boundary. It was pretty deep (for oceanic crust) so fits nicely in the correct place in this illustration: But megathrust earthquakes are not the only type of earthquake that can cause a tsunami. The 2009 magnitude M 8.1 extensional (normal) fault earthquake near Samoa and American Samoa caused a tsunami that inundated the nearby islands (causing lots of damage and human suffering). This tsunami also travelled across the Pacific Ocean to impact California! (This is why the California Tsunami Program monitors tsunami across the Pacific Basin, so that we can help reduce suffering through the evacuation of coastal areas. Remember, the entire coast of California is a Tsunami Hazard Area.)
Bathymetric map of the Tonga–Kermadec arc system. Map showing the depth of the subducted slab beneath the Tonga–Kermadec arc system. Louisville seamount ages are after Koppers et al.49 ELSC, eastern Lau-spreading centre; DSDP, Deep Sea Drilling Programme; NHT, Northern Havre Trough; OT, Osbourn Trough; VFR, Valu Fa Ridge. Arrows mark total convergence rates.
Earthquakes and subducted slabs beneath the Tonga–Fiji area. The subducting slab and detached slab are defined by the historic earthquakes in this region: the steeply dipping surface descending from the Tonga Trench marks the currently active subduction zone, and the surface lying mostly between 500 and 680 km, but rising to 300 km in the east, is a relict from an old subduction zone that descended from the fossil Vitiaz Trench. The locations of the mainshocks of the two Tongan earthquake sequences discussed by Tibi et al. are marked in yellow (2002 sequence) and orange (1986 series). Triggering mainshocks are denoted by stars; triggered mainshocks by circles. The 2002 sequence lies wholly in the currently subducting slab (and slightly extends the earthquake distribution in it),whereas the 1986 mainshock is in that slab but the triggered series is located in the detached slab,which apparently contains significant amounts of metastable olivine
bathymetry, and major tectonic element map of the study area. The Tonga and Vanuatu subduction systems are shown together with the locations of earthquake epicenters discussed herein. Earthquakes between 0 and 70 km depth have been removed for clarity. Remaining earthquakes are color-coded according to depth. Earthquakes located at 500–650 km depth beneath the North Fiji Basin are also shown. Plate motions for Vanuatu are from the U.S. Geological Survey, and for Tonga from Beavan et al. (2002) (see text for details). Dashed line indicates location of cross section shown in Figure 3. NFB—North Fiji Basin; HFZ—Hunter Fracture Zone.
Map showing distribution of slab segments beneath the Tonga-Vanuatu region. West-dipping Pacifi c slab is shown in gray; northeast-dipping Australian slab is shown in red. Three detached segments of Australian slab lie below the North Fiji Basin (NFB). HFZ—Hunter Fracture Zone. Contour interval is 100 km. Detached segments of Australian plate form sub-horizontal sheets located at ~600 km depth. White dashed line shows outline of the subducted slab fragments when reconstructed from 660 km depth to the surface. When all subducted components are brought to the surface, the geometry closely approximates that of the North Fiji Basin.
Previous interpretation of combined P-wave tomography and seismicity from van der Hilst (1995). Earthquake hypocenters are shown in blue. The previous interpretation of slab structure is contained within the black dashed lines. Solid red lines mark the surface of the Pacifi c slab (1), the still attached subducting Australian slab (2a), and the detached segment of the Australian plate (2b). UM—upper mantle;
Simplified plate tectonic reconstruction showing the progressive geometric evolution of the Vanuatu and Tonga subduction systems in plan view and in cross section. Initiation of the Vanuatu subduction system begins by 10 Ma. Initial detachment of the basal part of the Australian slab begins at ca. 5–4 Ma and then sinking and collision between the detached segment and the Pacifi c slab occur by 3–4 Ma. Initial opening of the Lau backarc also occurred at this time. Between 3 Ma and the present, both slabs have been sinking progressively to their current position. VT—Vitiaz trench; dER—d’Entrecasteaux Ridge.
Map of the Southwest Pacific Ocean showing the regional tectonic setting and location of the two dredged profiles. Depth contours in kilometres. The presently active arcs comprise New Zealand–Kermadec Ridge–Tonga Ridge, linked with Vanuatu by transforms associated with the North Fiji Basin. Colville Ridge–Lau Ridge is the remnant arc. Havre Trough–Lau Basin is the active backarc basin. Kermadec–Tonga Trench marks the site of subduction of Pacific lithosphere westward beneath Australian plate lithosphere. North and South Fiji Basins are marginal basins of late Neogene and probable Oligocene age, respectively. 5.4sK–Ar date of dredged basalt sample (Adams et al., 1994).
Large subduction-zone interplate earthquakes (large open gray stars) labeled with event date, Mw, GCMT focal mechanisms, and GPS velocity vectors (gray arrows and black triangles labeled with station name). GPS velocities are listed in Table 3. Black lines indicate the Tonga–Kermadec and Vanuatu trenches. Note that the 2009/09/29 Samoa–Tonga outer trench-slope event (Mw 8.1) triggered large interplate doublets (both of Mw 7.8; Lay et al., 2010). The Pacific plate subducts westward beneath the Australian plate along the Tonga–Kermadec trench, whereas the Australian plate subducts eastward beneath the Vanuatu arc and North Fiji basin. The opposite orientation between the Tonga–Kermadec and Vanuatu subduction systems is due to complex and broad back-arc extension in the Lau and North Fiji basins (Pelletier et al., 1998).
Regional map of moderate-sized (mb > 4:7) shallow-focus repeating earthquakes and background seismicity along the (a) Tonga–Kermadec and (b) Vanuatu (former New Hebrides) subduction zones. Shallow repeating earthquakes (black stars) and their available Global Centroid Moment Tensor (GCMT; Dziewoński et al., 1981; Ekström et al., 2003) are labeled with event date and doublet/cluster id where applicable. Colors of GCMT are used to distinguish nearby different repeaters. Source parameters for the clusters and doublets are listed in Tables 1 and 2. Background seismicity is shown as gray dots and large interplate earthquakes (moment magnitude, Mw > 7:3) since 1976 are shown as large open gray stars. Black lines indicate the trench (Bird, 2003) and slab contour at 50-km depth (Gudmundsson and Sambridge, 1998). Repeating earthquake clusters in the (a) T1 and T2 plate-interface regions in Tonga and (b) V3 plate-interface region in Vanuatu are used to study the fault-slip rate ( _d). A regional map of the Tonga–Kermadec–Vanuatu subduction zones is #EarthquakeReport for M 7.3 #Earthquake along outer rise near the Tonga trench reverse (compressional) mechanism south of analogues incl tsunamigenic 2009 M 8.1 (tho that was extensional)https://t.co/gQEdISt9eD learn more abt regional tectonics herehttps://t.co/eDsUON2Mly pic.twitter.com/DvMnY4rWck — Jason "Jay" R. Patton (@patton_cascadia) November 11, 2022 #EarthquakeReport for M 7.3 #Earthquake near the Tonga trench thrust (compressional) earthquake along the outer rise no #Tsunami observed on tide gages report here includes my interpretation and a regional tectonic summary:https://t.co/ze2s3bb7Vn pic.twitter.com/2M3SZaYE19 — Jason "Jay" R. Patton (@patton_cascadia) November 11, 2022 The region near todays M7.3 earthquake is incrediblely active due to the high rates of convergence between the Australian and Pacific Plates. Since 1900, 40 M7.5+ earthquakes have been recorded, as well as at least 3 M8+ events. https://t.co/avVOX0LcGH pic.twitter.com/dN9mIrwgwN — Wendy Bohon, PhD 🌏 (@DrWendyRocks) November 11, 2022 Fri Nov 11 10:48:00 2022 UTC * HAZARDOUS TSUNAMI WAVES FROM THIS EARTHQUAKE ARE POSSIBLE WITHIN 300 KM OF THE EPICENTER ALONG THE COASTS OF — よっしみ~☆🌏 (@yoshimy_s) November 11, 2022 Seismic waves from the Tonga 7.3 #earthquake, as arriving at a @raspishakEQ station of the @GEO3BCN_CSIC educational network in NE Iberia pic.twitter.com/K6YZPQf1JU — Jordi Diaz Cusi (@JDiazCusi) November 11, 2022 Recent Earthquake Teachable Moment for the M7.3 Tonga earthquake https://t.co/PJBT5jgOTy pic.twitter.com/h0kTCejygS — IRIS Earthquake Sci (@IRIS_EPO) November 11, 2022 Global surface and body wave sections from the M7.3 earthquake near Tongahttps://t.co/mz6A6vgD9F pic.twitter.com/0psyiRcDum — IRIS Earthquake Sci (@IRIS_EPO) November 11, 2022 Mw=7.3, TONGA ISLANDS REGION (Depth: 43 km), 2022/11/11 10:48:42 UTC – Full details here: https://t.co/vqxit49tby pic.twitter.com/m16qoCB5wK — Earthquakes (@geoscope_ipgp) November 11, 2022 Watch the waves from the M7.3 earthquake near Tonga roll across seismic stations in North America (THREAD 🧵) pic.twitter.com/hupVx0WfpQ — IRIS Earthquake Sci (@IRIS_EPO) November 11, 2022 Section from today's M7.3 earthquake in the Tonga region at 2022-11-11 10:48:45UTC recorded on the worldwide @raspishake network. See: https://t.co/LS1S4JlAqX. Uses @obspy and @matplotlib. pic.twitter.com/Jdz1FlEZN2 — Mark Vanstone (@wmvanstone) November 11, 2022 A cross-section of seismicity, with the focal mechanisms projected into the vertical plane, shows the three deep quakes with purple outlines. These events were close to the deepest quakes in this area, where the subducted slab possibly is deflected by the 670 km discontinuity. pic.twitter.com/V09EYGWJRd — Jascha Polet (@CPPGeophysics) November 11, 2022
I don’t always have the time to write a proper Earthquake Report. However, I prepare interpretive posters for these events. There was a magnitude M 7.6 earthquake in Mexico on 1 September 2022. https://earthquake.usgs.gov/earthquakes/eventpage/us7000i9bw/executive I am catching up on some Earthquake Reports that I did not yet post since my website was being migrated to a more secure and reliable server (and more expensive). The tectonics of coastal southwestern Mexico is dominated by the convergent plate boundary between the Cocos plate (to the southwest) and the North America plate (to the northeast). Here, the Cocos plate subducts below (goes underneath) the North America plate. The fault between these plates is called a megathrust subduction zone fault and the plate boundary forms the Middle America trench. This M 7.6 earthquake mechanism (the “moment tensor”) shows that this event was a compressional earthquake (reverse or thrust). Based on it’s location, the event probably happened along the megathrust fault. This earthquake even generated a tsunami recorded on tide gages in the region!
Development of the Tepic–Zacoalco (TZ), Colima, and Chapala rifts. The TZ rift is formed by the Rivera slab rollback, enhanced by the toroidal flow around the slab edges. The Colima rift is probably related with the oblique convergence between Rivera and NAM plates at ~5 Ma.
Tectonic setting of the Caribbean Plate. Grey rectangle shows study area of Fig. 2. Faults are mostly from Feuillet et al. (2002). PMF, Polochic–Motagua faults; EF, Enriquillo Fault; TD, Trinidad Fault; GB, Guatemala Basin. Topography and bathymetry are from Shuttle Radar Topography Mission (Farr&Kobrick 2000) and Smith & Sandwell (1997), respectively. Plate velocities relative to Caribbean Plate are from Nuvel1 (DeMets et al. 1990) for Cocos Plate, DeMets et al. (2000) for North America Plate and Weber et al. (2001) for South America Plate.
A. Geodynamic and tectonic setting alongMiddle America Subduction Zone. JB: Jalisco Block; Ch. Rift—Chapala rift; Co. rift—Colima rift; EGG—El Gordo Graben; EPR: East Pacific Rise; MCVA: Modern Chiapanecan Volcanic Arc; PMFS: Polochic–Motagua Fault System; CR—Cocos Ridge. Themain Quaternary volcanic centers of the TransMexican Volcanic Belt (TMVB) and the Central American Volcanic Arc (CAVA) are shown as blue and red dots, respectively. B. 3-D view of the Pacific, Rivera and Cocos plates’ bathymetrywith geometry of the subducted slab and contours of the depth to theWadati–Benioff zone (every 20 km). Grey arrows are vectors of the present plate convergence along theMAT. The red layer beneath the subducting plate represents the sub-slab asthenosphere.
Marine magnetic anomalies and fracture zones that constrain tectonic reconstructions such as those shown in Figure 4 (ages of anomalies are keyed to colors as explained in the legend; all anomalies shown are from University of Texas Institute for Geophysics PLATES [2000] database): (1) Boxed area in solid blue line is area of anomaly and fracture zone picks by Leroy et al. (2000) and Rosencrantz (1994); (2) boxed area in dashed purple line shows anomalies and fracture zones of Barckhausen et al. (2001) for the Cocos plate; (3) boxed area in dashed green line shows anomalies and fracture zones from Wilson and Hey (1995); and (4) boxed area in red shows anomalies and fracture zones from Wilson (1996). Onland outcrops in green are either the obducted Cretaceous Caribbean large igneous province, including the Siuna belt, or obducted ophiolites unrelated to the large igneous province (Motagua ophiolites). The magnetic anomalies and fracture zones record the Cenozoic relative motions of all divergent plate pairs infl uencing the Central American subduction zone (Caribbean, Nazca, Cocos, North America, and South America). When incorporated into a plate model, these anomalies and fracture zones provide important constraints on the age and thickness of subducted crust, incidence angle of subduction, and rate of subduction for the Central American region. MCSC—Mid-Cayman Spreading Center.
Rupture zones (ellipses) and epicenters (triangles and circles) of large shallow earthquakes (after KELLEHER et al., 1973) and bathymetry (CHASE et al., 1970) along the Middle America arc. Note that six gaps which have earthquake histories have not ruptured for 40 years or more. In contrast, the gap near the intersection of the Tehuantepec ridge has no known history of large shocks. Contours are in fathoms.
The study area encompasses Guerrero and Oaxaca states of Mexico. Shaded ellipse-like areas annotated with the years are rupture areas of the most recent major thrust earthquakes (M≥6.5) in the Mexican subduction zone. Triangles show locations of permanent GPS stations. Small hexagons indicate campaign GPS sites. Arrows are the Cocos-North America convergence vectors from NUVEL-1A model (DeMets et al., 1994). Double head arrow shows the extent of the Guerrero seismic gap. Solid and dashed curves annotated with negative numbers show the depth in km down to the surface of subducting Cocos plate (modified from Pardo and Su´arez, 1995, using the plate interface configuration model for the Central Oaxaca from this study, the model for Guerrero from Kostoglodov et al. (1996), and the last seismological estimates in Chiapas by Bravo et al. (2004). MAT, Middle America trench.
FOS = Resisting Force / Driving Force #EarthquakeReport for the M 7.6 (likely) subduction zone #Earthquake in #Mexico on 19 Sept 2022 catching up on reports that happened after my website went down generated 0.6-1.7m wave height #Tsunami — Jason "Jay" R. Patton (@patton_cascadia) November 9, 2022
I don’t always have the time to write a proper Earthquake Report. However, I prepare interpretive posters for these events. Because of this, I present Earthquake Report Lite. (but it is more than just water, like the adult beverage that claims otherwise). I will try to describe the figures included in the poster, but sometimes I will simply post the poster here. https://earthquake.usgs.gov/earthquakes/eventpage/us7000ilwt/executive This is possibly one of the most mysterious earthquakes of the year. I forgot to write this up at the time so need to fill in more details after I am done working up my annual summary.
I don’t always have the time to write a proper Earthquake Report. However, I prepare interpretive posters for these events. There was a magnitude M 6.9 earthquake in Taiwan on 18 September 2022. https://earthquake.usgs.gov/earthquakes/eventpage/us7000i90q/executive Taiwan is an interesting place, from a tectonic perspective. There is an intersection of several plate boundary fault systems here. Along the western boundary of Taiwan the Eurasia plate subducts (dives beneath) the Philippine Sea plate forming the Manila trench. This megathrust subduction zone fault system terminates somewhere in central-northern Taiwan. Intersecting central Taiwan from the east is another subduction zone where the Philippine Sea plate subducts beneath the Eurasia plate, forming the Ryukyu trench. There was an earthquake in Taiwan in 1999 that has been commemorated by creating a park and museum that preserves some of the evidence of the earthquake. This Chi-Chi earthquake cause lots of damage and, sadly, lots of suffering. In addition, because of the dominance of the computer chip manufacturing industry in Taiwan at the time, the price of computer chips was greatly inflated. The global economy suffered following this earthquake. This 18 September 2022 M 6.9 earthquake occurred on a crustal fault that strikes (trends) parallel to the coast. Because of the mapped faults, I interpret this to have been a left-lateral strike slip earthquake. There was a foreshock, a mag M 6.5 earthquake, nearby, the day before.
Geologic map of the Coastal Range on shaded relief (after Wang and Chen, 1993). The Longitudinal Valley Fault (LVF) can be subdivided into the Linding and Juisui locked Fault and the Chihshang and Lichi creeping Fault. Vertical cross-sections of VS perturbation tomography along the AeA0 and BeB0 profiles denote the Central Range, the Coastal Range, and the LVF. EU: Eurasian Plate; PH: Philippine Sea Plate.
A neotectonic snapshot of Taiwan and adjacent regions. (a) Taiwan is currently experiencing a double suturing. In the south the Luzon volcanic arc is colliding with the Hengchun forearc ridge, which is, in turn, colliding with the Eurasian continental margin. In the north both sutures are unstitching. Their disengagement is forming both the Okinawa Trough and the forearc basins of the Ryukyu arc. Thus, in the course of passing through the island, the roles of the volcanic arc and forearc ridge flip along with the flipping of the polarity of subduction. The three gray strips represent the three lithospheric pieces of Taiwan’s tandem suturing and disarticulation: the Eurasian continental margin, the continental sliver, and the Luzon arc. Black arrows indicate the suturing and disarticulation. This concept is discussed in detail by Shyu et al. [2005]. Current velocity vector of the Philippine Sea plate relative to the Eurasian plate is adapted from Yu et al. [1997, 1999]. Current velocity vector of the Ryukyu arc is adapted from Lallemand and Liu [1998]. Black dashed lines are the northern and western limits of the Wadati-Benioff zone of the two subducting systems, taken from the seismicity database of the Central Weather Bureau, Taiwan. DF, deformation front; LCS, Lishan-Chaochou suture; LVS, Longitudinal Valley suture; WF, Western Foothills; CeR, Central Range; CoR, Coastal Range; HP, Hengchun Peninsula. (b) Major tectonic elements around Taiwan. Active structures identified in this study are shown in red. Major inactive faults that form the boundaries of tectonic elements are shown in black: 1, Chiuchih fault; 2, Lishan fault; 3, Laonung fault; 4, Chukou fault. Selected GPS vectors relative to the stable Eurasian continental shelf are adapted from Yu et al. [1997]. A,Western Foothills; B, Hsueshan Range; C, Central Range and Hengchun Peninsula; D, Coastal Range; E, westernmost Ryukyu arc; F, Yaeyama forearc ridge; G, northernmost Luzon arc; H, western Taiwan coastal plains; I, Lanyang Plain; J, Pingtung Plain; K, Longitudinal Valley; L, submarine Hengchun Ridge; M, Ryukyu forearc basins.
Map of major active faults and folds of Taiwan (in red) showing that the two sutures are producing separate western and eastern neotectonic belts. Each collision belt matures and then decays progressively from south to north. This occurs in discrete steps, manifested as seven distinct neotectonic domains along the western belt and four along the eastern. A distinctive assemblage of active structures defines each domain. For example, two principal structures dominate the Taichung Domain. Rupture in 1999 of one of these, the Chelungpu fault, caused the disastrous Chi-Chi earthquake. The Lishan fault (dashed black line) is the suture between forearc ridge and continental margin. Thick light green and pink lines are boundaries of domains.
Proposed major sources for future large earthquakes in and around Taiwan. Thick red lines are proposed future ruptures, and the white patches are rupture planes projected to the surface. Here we have selected only a few representative scenarios from Table 1. Earthquake magnitude of each scenario is predicted value from our calculation.
#EarthquakeReport for M 6.9 #Earthquake in Taiwan on 18 September 2022 there was lots of damage and some casualties :-( landslides and liquefaction models show that there was a high likelihood for these.https://t.co/3tzXgvQl26 damage informationhttps://t.co/I95RUCSWkh pic.twitter.com/TPKL95vqHI — Jason "Jay" R. Patton (@patton_cascadia) November 9, 2022
There have not been that many large earthquakes this year. This is good for one main reason, there is a lower potential for human suffering. Therefore, there are fewer Earthquake Reports for this year. This morning (my time) there was a magnitude M 6.9 earthquake along the Romanche transform fault, a right-lateral strike-slip fault system that offsets the Mid Atlantic Ridge in the equatorial Atlantic Ocean. The fault is part of the Romanche fracture zone. https://earthquake.usgs.gov/earthquakes/eventpage/us7000i53f/executive The transform faults in this part of the Mid Atlantic Ridge plate boundary have a pattern of earthquakes that seem to max out in the lower 7 magnitudes. This may be (at least partly) due to the maximum length of these faults (?). The Romanche fault is about 900 kilometers long. The Chain fault is about 250 km long. The St. Paul fault is about 350 km long. Using empirical (data) based relations between earthquake subsurface rupture length and earthquake magnitude (Wells and Coppersmith, 1994), I calculate the maximum earthquake magnitude we may get on these three faults listed above. Here are the data that Wells and Coppersmith use to establish these relations.
(a) Regression of subsurface rupture length on magnitude (M). Regression line shown for all-slip-type relationship. Short dashed line indicates 95% confidence interval. (b) Regression lines for strike-slip relationships. See Table 2 for regression coefficients. Length of regression lines shows the range of data for each relationship.
Here are the magnitude estimates for each of these fault systems. Looking at the interpretive poster, we can see that there have not been any temblors that approach the sizes listed in this table. The largest historic earthquake was M 7.1 (there were several). So, we may ask ourselves one of the most common questions people ask regarding earthquakes. Was this M 6.9 a foreshock to a larger earthquake? Obviously, we cannot yet know this. Nobody can predict the future (at least not yet). However, based on the incredibly short historic record of earthquakes, we may answer this question: “no, probably not.” This answer is tempered by the very short seismic record. If magnitude 8 earthquakes occur, on average, every 1000 years, then our ~100 year record might be too short to “notice” one of these M 8 events. So, given the historic record, it sure seems likely that there may be another M6-7 earthquakes in the region of the fault sometime in the next couple of months. And, given our lack of knowledge about the long term behavior of these faults, it is also possible that there could be a larger M 8 event.
A: Multibeam topography of Romanche region, showing north-south profiles where sampling was carried out. Black dots and red numbers indicate estimated age (in million years) of lithosphere south of Romanche Transform, assuming spreading half-rate of 17 mm/yr within present-day ridge and transform geometry. White dots indicate epicenters of teleseismically recorded 1970–1995 events (magnitude . 4). FZ is fracture zone. B: Topography and petrology at eastern intersection of Romanche Fracture Zone with Mid-Atlantic Ridge. Data were obtained during expeditions S-16, S-19, and G-96 (Bonatti et al., 1994, 1996). C: Location of A along Mid-Atlantic Ridge.
Seismotectonic context. The map location is given by the red rectangle on the inset globe. Focal mechanisms are shown for events with Mw > 6 (ref. 30). Mw > 7.0 events are labelled. Stations of the PI-LAB ocean bottom seismometer network are indicated by triangles. Our relocated hypocentre and low-frequency RMT of the 2016 earthquake are shown by the red star and red beach ball, respectively. The orange beach ball is a colocated Mw 5.8 used for the Mach cone analysis. The black rectangle shows the location of the map in Fig. 2. ISC Bulletin, Bulletin of the International Seismological Centre.
Interpretation of rupture dynamics for the 2016 Romanche earthquake. Top: perspective view of bathymetry along the Romanche FZ. Bottom: interpretive cross-section along the ruptured fault plane. Colours show a thermal profile based on half-space cooling. The green line denotes the predicted transition between velocity-strengthening and velocity-weakening frictional regimes (as expressed by the a – b friction rate parameter) from Gabbro data35. The numbers show the key stages of rupture evolution: (1) rupture initiation (star) in the oceanic mantle, (2) initiation phase has sufficient fracture energy to propagate upwards to the locked section of fault, (3) weak subshear rupture front travels east in the lower crust and/or upper mantle, (4) rupture reaches the locked, thinner crustal segment close to the weaker RTI (SE1), (5) sufficient fracture energy for a westward supershear rupture in the crust along the strongly coupled fault segment (SE2) and (6) rupture possibly terminated by a serpentinized and hydrothermally altered fault segment.
#EarthquakeReport for M 6.9 #Earthquake along the equatorial Mid Atlantic Ridge plate boundary a right-lateral strike-slip earthquake along the Romanche transform faulthttps://t.co/LkglWJgBvD read the report herehttps://t.co/8ZGxTJEU9v pic.twitter.com/axcwlSPDSI — Jason "Jay" R. Patton (@patton_cascadia) September 5, 2022 Mw=7.0, CENTRAL MID-ATLANTIC RIDGE (Depth: 25 km), 2022/09/04 09:42:18 UTC – Full details here: https://t.co/MaNnp6eDAU pic.twitter.com/Gv39KoU3KQ — Earthquakes (@geoscope_ipgp) September 4, 2022 Magnitude 6.9 #earthquake on the mid-Atlantic ridge a couple of hours ago (2022-09-04Z09:42) https://t.co/GwKH4H1yON Predominantly strike-slip (as expected there). Amazing T-phases on the Ascension island hydrophones (data via @IRIS_EPO) coming after the weaker converted P-wave. pic.twitter.com/rCwawAet0W — Dr. Steven J. Gibbons (@stevenjgibbons) September 4, 2022 Major M6.9 right lateral fault #eartquake in oceanic Romanche fracture zone, offsetting central Mid-Atlantic Ridge (3cm/y). Large one for geologic setting, but no surface impact; no tsunami. Textbook behavior. #geohazards https://t.co/F3hXqtkikg pic.twitter.com/KcHL6p1nca — 🌎 Prof Ben van der Pluijm ⚒️ (@vdpluijm) September 4, 2022 Magnitude 6.9 earthquake on the Mid-Atlantic ridge, recorded in New England – detected in Maine, Massachusetts and the Westport Observatory's seismic equipment 4,340 miles from the epicenter in the middle of the Atlantic ocean. @Weston_Quakes https://t.co/dS9MJOU3ow pic.twitter.com/wUJwQ8XBqh — WestportAstroSociety (@westportskyguys) September 4, 2022 2022-09-04 strong M6.9 Central Mid-#Atlantic Ridge #earthquake recorded by online high quality data #RaspberryShakes + 3D trace from Canindé de São Francisco, #Brazil (2031.6km away) + area historical seismicity.#Python @raspishake @matplotlib #CitizenScienc pic.twitter.com/QYqq7lJPaW — Giuseppe Petricca (@gmrpetricca) September 4, 2022
I don’t always have the time to write a proper Earthquake Report. However, I prepare interpretive posters for these events. https://earthquake.usgs.gov/earthquakes/eventpage/us6000i5rd/executive 20220727_philippines_interpretation.pdf 16 MB pdf #EarthquakeReport for M7.1 #Lindol #Earthquake in the #Philippines Shaking reported up to MMI 9! See more abt regional tectonics herehttps://t.co/kZy1TFpDgN USGS page herehttps://t.co/GI4mzfeu0Y pic.twitter.com/pzMzWJDmxm — Jason "Jay" R. Patton (@patton_cascadia) July 27, 2022 I don’t always have the time to write a proper Earthquake Report. However, I prepare interpretive posters for these events. Because of this, I present Earthquake Report Lite. (but it is more than just water, like the adult beverage that claims otherwise). I will try to describe the figures included in the poster, but sometimes I will simply post the poster here. https://earthquake.usgs.gov/earthquakes/eventpage/us6000h6nr/executive I will fill in these details a bit more after I complete the annual summary.
Earthquake Report: M 6.4 Gorda plate
Initial Narrative
The Earthquake Report
Below is my interpretive poster for this earthquake
I include some inset figures. Some of the same figures are located in different places on the larger scale map below.
Seismicity Profile
Aftershock Patterns
(www.earthscope.org).
Mapped Geology
Earlier Report Interpretive Posters
Some Relevant Discussion and Figures
I have compiled some literature about the CSZ earthquake and tsunami. Here is a short list that might help us learn about what is contained within the core that I collected.
Mendocino triple junction video
Shaking Intensity
Shaking Intensity and Potential for Ground Failure
Seismic Hazard and Seismic Risk
Stress Triggering
[1993] model for the 1992 Cape Mendocino earthquake (J). Calculation depth is 5 km. The numbered brackets are groups of aftershocks from Hill et al. [1990].
Cascadia subduction zone
General Overview
Earthquake Reports
Gorda plate
Blanco transform fault
Mendocino fault
Mendocino triple junction
North America plate
Explorer plate
Uncertain
Social Media
i plotted USGS Slab2 depths https://t.co/HdW0ZOzted
i traced Gorda slab from Guo 2021 B-B' https://t.co/t8gXg1jaYY
see: https://t.co/t8gXg1jaYY
M5.4 – right-lateral s-s (in mantle?)
high likelihood for eq induced liquefaction
Thanks to the seismic records provided in particular by IRIS, SCEDC pic.twitter.com/VOEflZWynp
Felt by at least 9.0 m. people.
More than 130k people live in regions, where damage can be expected.
Severe damage is expected in an area affecting more than 50k people.https://t.co/9Ku6UPu3gQ pic.twitter.com/6UN4tIasme
https://t.co/s2By2z6zDh
(preliminary data processing) https://t.co/7RGCxkHmZ5 pic.twitter.com/4FiIYo5EDC
Most vulnerable to any strong shaking are "unreinforced masonry" buildings like the old Humboldt Creamery in Loleta. 1/7 pic.twitter.com/ZCInnRJv6k
References:
Basic & General References
Specific References
Return to the Earthquake Reports page.
Earthquake Report: M 6.9 Sumatra
I need to run to catch the sunset and will complete the intro later tonight.
Below is my interpretive poster for this earthquake
I include some inset figures. Some of the same figures are located in different places on the larger scale map below.
Other Report Pages
Some Relevant Discussion and Figures
Seismic Hazard and Seismic Risk
Tsunami Hazard
Indonesia | Sumatra
General Overview
Earthquake Reports
Social Media
ID: #rs2022wsherl
Southwest of Sumatra, Indonesia
2022-11-18 13:37 UTC@raspishake #QuakeView
ID: #rs2022wsherl
Southwest of Sumatra, Indonesia
2022-11-18 13:37 UTC@raspishake #QuakeView
References:
Basic & General References
Specific References
Return to the Earthquake Reports page.
Earthquake Report: M 7.3 Tonga trench outer rise
Below is my interpretive poster for this earthquake
I include some inset figures. Some of the same figures are located in different places on the larger scale map below.
Other Report Pages
Some Relevant Discussion and Figures
TZ—transition zone; LM—lower mantle.
shown in the inset figure, with the gray dotted box indicating the expanded region in the main figure.
New Britain | Solomon | Bougainville | New Hebrides | Tonga | Kermadec Earthquake Reports
General Overview
Earthquake Reports
Social Media
Mag: 7.5 Depth: 33
Coords: 19.322 S 172.01 W
Location: TONGA ISLANDS REGION
NIUE AND TONGA pic.twitter.com/lm1RMEJ0o8
References:
Basic & General References
Specific References
Return to the Earthquake Reports page.
Earthquake Report: M 7.6 Earthquake in Mexico
Because of this, I present Earthquake Report Lite. (but it is more than just water, like the adult beverage that claims otherwise). I will try to describe the figures included in the poster, but sometimes I will simply post the poster here.Below is my interpretive poster for this earthquake
I include some inset figures.
Supportive Figures
Earthquake Triggered Landslides
Social Media:
probably triggered landslides/induced liquefactionhttps://t.co/9zpN2ZlAhw pic.twitter.com/tMDb4mSwCw
Mexico | Central America
General Overview
Earthquake Reports
References:
Basic & General References
Specific References
Return to the Earthquake Reports page.
Earthquake Report: M 6.0 northeast Pacific Ocean
Below is my interpretive poster for this earthquake
I include some inset figures.
Pacific Ocean | Hawai’i’ Earthquake Reports
References:
Basic & General References
Specific References
Return to the Earthquake Reports page.
Earthquake Report for M 6.9 Earthquake in Taiwan
Because of this, I present Earthquake Report Lite. (but it is more than just water, like the adult beverage that claims otherwise). I will try to describe the figures included in the poster, but sometimes I will simply post the poster here.Below is my interpretive poster for this earthquake
I include some inset figures.
Supportive Figures
Social Media:
India | Asia | India Ocean
Earthquake Reports
References:
Basic & General References
Specific References
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Earthquake Report: M 6.9 Mid Atlantic Ridge
Earthquake magnitude is controlled by three things:
If we continue to look at the historic record, we will see that there appear to be three instances where one of these M 6.5-7 earthquakes had a later earthquake of a similar magnitude.
When an earthquake fault slips, the crust surrounding the fault squishes and expands, deforming elastically (like in one’s underwear). These changes in shape of the crust cause earthquake fault stresses to change. These changes in stress can either increase or decrease the chance of another earthquake.
I wrote more about this type of earthquake triggering for Temblor here. Head over there to learn more about “static coulomb stress triggering.”
In the poster, I label these earthquakes as “Linked Earthquakes.” Perhaps the later of each earthquake pair (or triple) was triggered by the change in static coulomb stress.
Here are the three sets of “Linked Earthquakes:”
Since we cannot yet know the real answer to this question, we are reminded of the advice that educators and emergency response people provide: If one lives in Earthquake Country, get earthquake prepared. Just a little effort to get better prepared makes a major difference in the outcome.
Head over to Earthquake Alliance where there are some excellent brochures about how to be better prepared and more resilient to earthquake and tsunami hazards. Living on Shaky Ground is one of my favorites!Below is my interpretive poster for this earthquake
I include some inset figures. Some of the same figures are located in different places on the larger scale map below.
Some Relevant Discussion and Figures
Atlantic
General Overview
Earthquake Reports
Social Media
References:
Basic & General References
Specific References
Return to the Earthquake Reports page.
Earthquake Report M 7.0 Philippines
Because of this, I present Earthquake Report Lite. (but it is more than just water, like the adult beverage that claims otherwise). I will try to describe the figures included in the poster, but sometimes I will simply post the poster here.Below is my interpretive poster for this earthquake
I include some inset figures.
Philippines | Western Pacific
Earthquake Reports
References:
Basic & General References
Specific References
Social Media: Here is my thread for this event.
This has potential to be quite devastatingReturn to the Earthquake Reports page.
Earthquake Report M 6.7 in Taiwan
Below is my interpretive poster for this earthquake
I include some inset figures.
India | Asia Earthquake Reports
Earthquake Reports
References:
Basic & General References
Specific References
Return to the Earthquake Reports page.