Earthquake Report: M 7.7 Panamá

Two weeks ago there was a magnitude M 7.7 earthquake in southern/central Panamá, along the Azuero Peninsula.

The earthquake was shallow and within the crust of the Panama microplate.

https://earthquake.usgs.gov/earthquakes/eventpage/us6000u18k/executive

The earthquake mechanism is strike-slip (the beach ball shaped graphic looks like a checkerboard).

The tectonics of much of central america are dominated by the subduction zone (convergent plate boundary) that forms the Middle America trench. The large magnitude megathrust earthquakes occur on slip along this fault.

This subduction zone appears to cease in activity about in western Panamá/eastern Costa Rica.

South of Panamá there is a series of north-south striking right-lateral strike-slip faults (transform plate boundary faults) associated with the Panama fracture zone.

To the east of the Panama fracture zone, there is a major strike-slip plate boundary fault that runs roughly east-west parallel to the coastline/continental slope.

This left-lateral strike-slip fault separates the Panama microplate to the north from the Nazca plate to the south and is called the South Panama Deformation Belt (SPDB).

In the transition from strike-slip on the east to subduction on the west, the crustal faults include sections of both strike-slip faults and reverse faults (plus some normal faults offshore).

In the region of the Azuero Peninsula, there is a large left-lateral strike-slip fault that strikes west-northwest across the southern peninsula.

Based on the aftershock pattern and the U.S. Geological Survey finite fault slip model, this M 7.7 earthquake suggest that the entire mapped fault slipped.

The aftershock pattern measures a fault length of ~190 km. The USGS finite fault model shows a composite fault length of ~150 km.

Wells and Coppersmith (1994) fault scaling relations are based on empirical correlations between fault slip data (like fault length, slip, etc.) and earthquake magnitude.

Wells and Coppersmith (1994) scaling relations suggest for a magnitude M 7.7 earthquake, the fault would have a subsurface rupture length.

So, basically, this fault fits well into those scaling relations.


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 1926-2026 with magnitudes M ≥ 6.0 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 of the same figures are located in different places on the larger scale map below.

  • Here is the map with a month’s seismicity plotted.


  • Here is the updated map with the updated USGS finite fault slip model.


Other Report Pages

Shaking Intensity

  • Here is a figure that shows a more detailed comparison between the modeled intensity and the reported intensity. Both data use the same color scale, the Modified Mercalli Intensity Scale (MMI). More about this can be found here. The colors and contours on the map are results from the USGS modeled intensity. The DYFI data are plotted as colored dots (color = MMI, diameter = number of reports).
  • In the upper panel is the USGS Did You Feel It reports map, showing reports as colored dots using the MMI color scale. Underlain on this map are colored areas showing the USGS modeled estimate for shaking intensity (MMI scale).
  • In the lower panel is a plot showing MMI intensity (vertical axis) relative to distance from the earthquake (horizontal axis). The models are represented by the green and orange lines. The DYFI data are plotted as light blue dots. The mean and median (different types of “average”) are plotted as orange and purple dots. Note how well the reports fit the green line (the model that represents how MMI works based on quakes in California).
  • Below the map and the lower plot is the USGS MMI Intensity scale, which lists the level of damage for each level of intensity, along with approximate measures of how strongly the ground shakes at these intensities, showing levels in acceleration (Peak Ground Acceleration, PGA) and velocity (Peak Ground Velocity, PGV).


Potential for Ground Failure

  • Below are a series of maps that show the potential for landslides and liquefaction. These are all USGS data products.
    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.


  • Here Dr. Bohon demonstrates the phenomena of liquefaction.
    • @drwendyrocksit #Liquefaction is a process by which water-saturated sediment temporarily loses strength and acts as a fluid. This can happen during #earthquake shaking. #geophysics #geology ♬ Quicksand – Hatchie

  • And, another video demonstration.

  • 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.


  • Below is the liquefaction susceptibility and landslide probability map (Jessee et al., 2017; Zhu et al., 2017). Please head over to that report for more information about the USGS Ground Failure products (landslides and liquefaction). Basically, earthquakes shake the ground and this ground shaking can cause landslides.
  • I use the same color scheme that the USGS uses on their website. Note how the areas that are more likely to have experienced earthquake induced liquefaction are in the valleys. Learn more about how the USGS prepares these model results here.


    •

Some Relevant Discussion and Figures: Regional Tectonics

    • Here is the tectonic overview figure from Hoernle et al. (2002).


      • Gala´pagos Islands and hotspot tracks (Cocos, Coiba, Malpelo, and Carnegie Ridges), igneous complexes in Central America with Gala´pagos geochemical affinities, and western portion of Caribbean plate. Is. is Island, S.C. is spreading
      center.

    • This is another good overview map that shows the spreading center that creates the Nazca and Cocos plates (Coates et al., 2004).


      • Map of southern Central America (dark shading) and the Panama microplate (pale shading). Darien is picked out in pale shading. Dashed lines with teeth mark zones of convergence; zippered line is Panama-Colombia suture. Very heavy dashed line marks location of Neogene volcanic arc; black circles mark Paleogene-Eocene volcanic arc. NPDB – North Panama deformed belt; SPDB – South Panama deformed belt; PFZ – Panama fracture zone. Principal Neogene sedimentary basins located by striped ovals.

    • Here is a map showing an early interpretation of the magnetic anomalies of the Panama Basin (Lonsdale and Klitgord, 1978). The following 2 figures show an example of how shipboard measurements of magnetic intensity are interpreted for the seafloor shown in this figure. The gray bands are parts of the oceanic crust that share a similar magnetic polarity and a similar range in ages. They also present their interpretations of the crustal structures in the region. Recall that this map was prepared long before we had the excellent detailed bathymetry data that we may view in Google Earth (prepared as an inversion of gravity data collected from satellites and the Space Shuttle). Many of the subsequent interpretations of the tectonics in the region is based on this initial analysis.


      • Crustal structure between Malpelo and Panama, showing 1965 to 1975 epicenters (defining present plate boundaries), magnetic anomalies, tracks of profiles shown in Figures 6 and 8, and locations of sampling sites.

    • Here is a map showing the magnetic intensity observations as recorded from research cruises (Lonsdale and Klitgord, 1978). The wiggles are shown along the ship tracklines. The next figure shows one example of these magnetic profiles and how they interpret these data into the magnetic anomaly map of the seafloor.


      • Magnetic anomalies between Malpelo and Carnegie Ridges, numbered according to time scales listed in caption of Figure 2. Note anomaly 5 to 5B sequence along long 81°W, mirrored around extinct Malpelo rift spreading center at lat 1°40’N. Magnetic anomalies on western (Costa Rica rift) segment are from Hey and others (1977). Tracks are labeled for Conrad 11.11 (CON 11) Yaloc 69 (Y 69), Iguana 3, Cocotow 2 (CCTW 2), Cocotow 3 (CCTW 3), F. Drake 3 (FD 3), and some lines of Oceanographer 70 (OC 70). Unlabeled profiles on Costa Rica rift are from Oceanographer 69; those on Malpelo rift are from Oceanographer 70.

    • Here is the profile from Malpelo Ridge to Carnegie Ridge (Lonsdale and Klitgord, 1978). They present the observations compared to their modeled results at the top and a bathymetric profile along with sediment thickness on the bottom.


      • Profile of Cocotow 3 traverse between Malpelo and Carnegie Ridges (see Fig. 4 for location). Synthetic magnetic profile was generated using reversal time scale discussed in Figure 2 caption, spreading rates indicated at top of this figure, magnetization of 4 A/m, and magnetized layer that is 500 m thick and has an upper surface that coincides with basement relief. Note that anomaly match is poor
      within 50 to 100 km of Carnegie and Malpelo Ridges. Fit could have been improved by postulating a somewhat faster spreading rate for this region, but even so, we could not achieve as good a match as for central part of profile.

    • This is the result of their analyses (Lonsdale and Klitgord, 1978). These authors prepared a tectonic reconstruction given their knowledge of crustal structures and magnetic anomaly data.


      • Tectonic reconstructions tracing inferred history of eastern Panama Basin. (A) Middle Oligocene: Farallon plate interacting with Caribbean and South American plates, just before splitting into Nazca and Cocos plates. (B) Middle Miocene: Malpelo and Carnegie Ridges are being formed by hot spot centered on Nazca plate near axis of Nazca-Cocos spreading and are being continuously separated by spreading at boundary. (C) Late Miocene: slowdown of spreading on Malpelo rift, rejuvenation of fracture zone at long 83°W, and cessation of subduction at Panama Trench. (D) Early Pliocene: continued northward migration of Cocos Ridge, stagnation of Malpelo Ridge, and uplift of Coiba Ridge near Nazca-Cocos-Caribbean triple junction. (E) Pleistocene: Cocos and Carnegie Ridges have just arrived at Middle America and Ecuador Trenches, and triple junction has jumped west from Coiba to Panama fracture zone.

    • Here is the map from Meschede and Barchkausem (2000) that shows the complexity of the spreading ridges and the fracture zones in the region.


      • Overview of the eastern Panama Basin (modified from Meschede et al., 1998). Numbers indicate the ages of oceanic crust. The distribution of extinct spreading systems is from Meschede et al. (1998). CNS = Cocos-Nazca spreading system. RSB = rough/smooth boundary.

    • Here is the figure from Camacho (1991) showing their analysis of the faults and earthquake mechanisms from teh 1934 series of earthquakes (and others too). I include their focal mechanism in the posters above.


      • Map depicting lhe southwestern Panama continental manin and lhe Panama-Coiba Fracture Zone wilh some of its characteristic focal mechanisms.

    • Here is the detailed map from Marcaillou et al. (2006) showing the ages of the seafloor for the Panama Basin (the oceanic crust near and east of the PFZ).


      • Interpretation of the pattern of crustal isochrons (Hardy 1991; Lonsdale 2005) and plate boundaries in the Panama Basin (modified from Lonsdale 2005). Earthquakes (black dots) and fault plane solution are from the Harvard University archive of centroid-moment tensor solutions. Plain lines are active spreading axis and transform faults: Costa Rica Rift (CRR) and Panama Fracture Zone (PFZ). Dashed and dotted lines are fossil spreading axis and transform faults: Buenaventura Rift (BR), Malpelo Rift (MR), Coiba Fracture Zone (CFZ) and Yaquina Graben. Possible spreading activity along Sandra Rift (SR) is still in discussion.

      • The interaction of the Cocos Ridge with the MAT appears to be a key part of the tectonics associated with the PFZ. Here is the plate tectonic map from Morell et al. (2012).
      • My original maps included left-lateral strike-slip arrows on the subduction zone east of the PFZ because I had interpreted this as likely given the obliquity of relative plate motion there, but I was unsure if this was reasonable (I had not seen any maps showing this). Given the analysis by Dr. Morell, I have replaced these arrows in the interpretive posters. Sometimes it is good to go with one’s interpretations of their observations, regardless if they find these interpretations elsewhere. Good lesson.


        • (a) Digital elevation model of the plate tectonic setting surrounding the Cordillera de Talamanca (CT), southern Costa Rica and Cordillera Central (CC), western Panama. Tectonic plates shown are the Cocos plate (CO), Nazca plate (NZ), Caribbean plate (CA), Panama microplate (PM), with plate velocities relative to a fixed CA plate [Bird, 2003; DeMets et al., 1990; DeMets, 2001; Jin and Zhu, 2004; Kellogg and Vega, 1995]. MAT, Middle America Trench; EPR, East Pacific Rise; CNS-2, Cocos-Nazca-Spreading; PTJ, Panama Triple Junction; PFZ, Panama Fracture Zone; BFZ, Balboa Fracture Zone; CFZ, Coiba Fracture Zone; NP, Nicoya Peninsula; AG, Aguacate Range; OP, Osa Peninsula; BP, Burica Peninsula; FCTB, Fila Costeña Thrust Belt; NPDB, North Panama Deformed Belt; TV, Tisingal Volcano; IV, Irazú volcano; BV, Barú volcano; YV, La Yeguada volcano; EV, El Valle volcano. Bathymetric data supplied by ETOPO1 combined from Amante and Eakins [2009], Smith and Sandwell [1997], and Ranero et al. [2003]. Topography supplied by CGIR-CSI based on NASA’s SRTM4 data set. White triangles indicate active volcanoes. Yellow dashed lines indicate on-land projection of Cocos Ridge boundaries. (b) Inset showing location of Figure 1a based on ETOPO1 data. SA refers to the South American plate. (c) Velocity triangle for Panama Triple Junction. CR represents the axis of the Cocos Ridge. Red lines denote the PM-CO and PM-NZ vectors, respectively. Numbers shown are in mm/yr.

      • This figure shows how Dr. Morell interprets how the PFZ projects beneath the upper plate (Morell et al. (2013). Note how the faults in the Fila Costeña Thrust Belt terminate where this tear is projected.


        • Map of southern Central America, showing plate tectonic setting surrounding the Panama triple junction (PTJ) and Barú Volcano based on a stable Caribbean plate (DeMets et al., 1990; Kellogg and Vega, 1995; DeMets, 2001; Bird, 2003). MAT—Middle America Trench; CO—Cocos plate; NZ—Nazca plate; CA— Caribbean plate; PM—Panama micro plate; PTJ—Panama triple junction; PFZ—Panama fracture zone; BFZ—Balboa fracture zone; CFZ—Coiba fracture zone; TV—Tisingal Volcano; OP—Osa Peninsula; BP—Burica Peninsula; VG— Valle General. Elevations are based on National Aeronautics and Space Administration’s (NASA) SRTM v4 imagery. Bathymetry is combined from ETOPO1 and Ranero et al. (2003). Thrusts and shortening estimates outlined for Fila Costeña thrust belt are combined from Sitchler et al. (2007), Fisher et al. (2004), and Morell et al. (2008). Fault traces on Burica Peninsula are from Morell et al. (2011a) and back arc is from Brandes et al. (2007). Contour interval for bathymetry is 250 m.

      • The following two figures show the Tertiary to recent tectonic reconstructions from Morell (2015). These reconstructions are based on relative plate motion rates as constrained by magnetic anomalies mapped in the oceanic crust, as well as GPS and plate circuit relative plate motions from other researchers (e.g. MOREVEL from DeMets et al., 2010 and others). Frist we see the Morell (2015) magnetic anomaly map, then the plate history maps.


        • Digital elevation model [Smith and Sandwell, 1997; Amante and Eakins, 2009] showing Panama Basin and seafloor magnetic anomaly data surrounding the southern Central America subduction zone [Lonsdale and Klitgord, 1978; Wilson and Hey, 1995; Barckhausen et al., 2001; Lonsdale, 2005] based on chron time scale of Cande and Kent [1995]. The 22000 m contour is shown for prominent bathymetric features in the region, including Malpelo Ridge (MaR) and Coiba Ridge (CoR). BFZ, Balboa Fracture Zone; CFZ, Coiba Fracture Zone; CNS, Cocos-Nazca spreading center; COL, Colombia; CR, Costa Rica; EC, Ecuador; GHS, Galapagos hot spot; MR, Malpelo Rift; MAT, Middle America Trench; MoR, Morgan Rift; NI, Nicaragua; PA, Panama; PFZ, Panama Fracture Zone; SR, Sandra Rift; YG, Yaquina Graben. Inset: Present day plate boundaries of Cocos (CO), Nazca (NZ), Caribbean (CA), and South American (SA) plates. East Pacific Rise (EPR) and Cocos-Nazca Spreading Center (CNS) are also shown.


        Plate reconstruction models for the Cocos (CO) and Nazca (NZ) plates relative to the Caribbean plate from 4 Ma to recent. BFZ, Balboa Fracture Zone; CaR, Carnegie Ridge; CFZ, Coiba Fracture Zone; CNS, crust derived from the Cocos-Nazca spreading center; CocR, Cocos Ridge; CoR, Coiba Ridge; CR, Costa Rica; EPR, crust derived from the East Pacific Rise; GH, Galapagos hot spot; MaR, Malpelo Ridge; MoR, Morgan Rift; MR, Malpelo Rift; PA, Panama; PFZ, Panama Fracture Zone; PTJ, Panama Triple Junction; RSB, rough-smooth boundary; SMD, seamount domain; SR, Sandra Ridge; YG, Yaquina Graben.


        Plate reconstruction models for the Cocos and Nazca plates relative to the Caribbean plate from 6 to 10 Ma. CaR, Carnegie Ridge; CFZ, Coiba Fracture Zone; CNS, crust derived from the Cocos-Nazca spreading center; CocR, Cocos Ridge; CR, Costa Rica; EPR, crust derived from the East Pacific Rise; GH, Galapagos hot spot; MaR, Malpelo Ridge; MR, Malpelo Rift; PA, Panama; PFZ, Panama Fracture Zone; PTJ, Panama Triple Junction; SMD, seamount domain, SR, Sandra Ridge; YG, Yaquina Graben.

      • Here is a map from Burke et al. (1984) that shows their interpretation of the region through time.
      • Note from C onward, there is a strike-slip fault system that brings the southern Central America into place.
      • This is the strike-slip plate boundary that currently separates the Panama microplate to the north from the Nazca plate to the south, just east of the Panama fracture zone.


        • General outline of Caribbean/Gulf of Mexico evolution in the framework of relative motion rectors (see Fig. 2a and Pindell and Dewey, 1982). Three general phases of geologic development are predicted here from consideration of North America-South America relative plate motion; a fourth is not predicted and is shown in Figure 9. The three phases are: 1) Jurassic-Lower Cretaceous extension sinistral slip and development of predominately stable shelf margins (crosses=evaporites; W=Wiggins Arch; S=Sabine Arch; Y=Yucatan block; C=Chortis block; B=Bahama Platform; CT=Chihuahua Trough; V=volcanic arc; barbed lines=thrusts or subduction zones; barb on hanging wall; arrows=a displacement of points relative to a fixed North America—Fig. 7a); 2) Cretaceous-Paleogene convergence of South America with respect to North America with development of several arc terrains (GA= Greater Antilles; p-cr=Panama-Costa Rica arc) with at least two episodes of arc-continent collisions western Greater Antilles with Yucatan block at Motagua suture zone (MZ) and the Netherlands Antilles (n.a.) with northern South America; B” oceanic plateau may have undergone sinistral shear along faults like the Hess escarpment (h.e.) as a response to oblique motion of the Americas (see vector triangle) (Fig. 7b, c, d); 3) post-Eocene eastward relative motion of the Caribbean plate with respect to the Americas and development of the complex North and South Caribbean strike-slip plate boundary zones (Fig. 7e, f)- Shapes of landmasses, particularly northern South America, have been severely altered by this strike-slip phase, as well as a subsequent collisional phase (Fig. 9) and are shown in earlier time frames only as approximate geographical references.

    Some Relevant Discussion and Figures: Local Tectonics

      • Here is a map from Trenkamp et al. (2002) that shows GPS plate motions.
      • Each GPS site velocity is plotted as a vector showing motion relative to stable South America.


        • Station velocity vectors relative to stable South America at 95% confidence using the data from the 1991, 1994, 1996, and 1998 CASA campaigns. The Cocos Island vector (COCO) was calculated relative to South America using a vector reported in Freymueller et al., (1993). Location of the COCO vector has been shifted to maintain the clarity of the figure.

      • This map from Buchs et al. (2011) shows the regional tectonic setting.
      • The next map is a detailed geologic/fault map designated by the rectangle centered on Azuelo Peninsula.


        • General setting of the Azuero Marginal Complex and Azuero Accretionary Complex (after Buchs et al., 2010).

      • This shows the detailed geologic and fault mapping for Azuero Peninsula (Buchs et al., 2011).


        • Geological Map of the Azuero area modified from the Geologic Map of Panama, scale 1:250,000 (Mapa Geológico República de Panamá, Dirección General de Recursos Minerales, 1991). This map also synthesizes the early work by Terry (1956) and several informal reports produced in the frame of the United Nations Development Program (del Giudice and Recchi, 1969; Metti and Recchi, 1976; Metti et al., 1972; Recchi and Miranda, 1977). Offshore faults are from Kolarsky et al. (1995a).

      • Here is an older map showing the crustal faults throughout the region from Silver et al. (1990).
      • Not much is different on modern maps compared to this older map.


        • Summary tectonic map of Panama and vicinity. Locations of major fault zones indicated: thrusts have triangular teeth on upper plates; other fault types are not distinguished. Locations of seismic lines 11, 26, 48, and 39. Also located are geographic features mentioned in the text.

      • Here is a map from Ortiz Guerrero (2023) that shows the local tectonics of the Panama region.
      • They plot the ages of magmatic rocks by color. These authors use these and other data (geologic mapping, gravity modeling) to interpret the timing of different configurations along this plate boundary (e.g., seamount collision, ophiolite accretion, and whole margin deformation).


        • Regional setting of the Azuero Peninsula. Modified from Montes et al. (2012); bathymetry and shaded topography from Geomapapp. Ages of magmatic rocks (in pattern), coloured by age. See SM1 for compilation of ages and authors.

      • Rockwell and others conducted substantial work to help characterize the seismic hazards for the Panama canal. They published a number of papers, which included the paleoseismic evidence to support the hazards analayses.
      • Here is a map from Rockwell et al. (2010a) that shows relative plate motions using vectors that represent GPS monument relative velocities. Note how the plate motions in Panama, east of the Panama fracture zone, are parallel to the South Panama Deformation Belt (SPDB).


        • Modern tectonic setting of Central America (modified from WLA [2007]). GPS stations used in this paper are indicated by the blue stars, and their names are the same as used by Trenkamp et al. [2002].

      • This is a series of maps that show the Rockwell et al. (2010a) plate model interpretations.


        • (a) Generalized map of principal faults in Panama, including the North Panama Deformation Belt (NPDB), the South Panama Deformation Belt (SPDB), the Azuero‐Sunu fault zone (A‐SFZ), faults in the Darien region, including the Sanson Hills fault (SHF), and the Rio Gatun and Limon‐Pedro Miguel fault zones (RGF, L‐PMF). (b) Primary faults used in the block model. Faults are extended to connect with others to form blocks. Some folding and bending of Panama is also assumed in the northeastern part of the model, which is largely what drives the faults in Darien. (c) Retrodeformed block model of Panama, with the amount of back slippage consistent with the known fault rates for 3 Ma. Eastern Panama is assumed to have buckled northward, resulting in oroclinal flexure of the isthmus and forcing slip on the faults in the Darien region. (d) Simplified fault block model to test the consistency between GPS‐derived motions, fault slip rate estimates, and the general pattern of deformation predicted by the retrodeformed block model. Model rates (red vectors) represent block translations relative to crustal block CPAN. Block ids (explained below) are shown next to the base of the block motion vectors. Residual velocities (green) are relative to a no‐net translation reference frame. Site names are shown next to the base of the residual vectors. Error ellipses represent 95% confidence level. The residual velocity at CARI is 6 mm/yr for scale. Strike slip rate estimates shown next to select fault segments; cyan, right lateral; orange, left lateral. Block ids correspond to geographic regions referred to in the text as follows: CARI, Caribbean; NPAN, North Panama; CPAN, central Panama; SPAN, southern Panama; DARI, Darien; SOAM, South America; COCO, Cocos plate; NAZC, Nazca plate. Fault segment ids are defined in Table 2.

      Social Media

      References:

      Basic & General References

    • 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.
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    • 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
    • Storchak, D. A., D. Di Giacomo, I. Bondár, E. R. Engdahl, J. Harris, W. H. K. Lee, A. Villaseñor, and P. Bormann (2013), Public release of the ISC-GEM global instrumental earthquake catalogue (1900–2009), Seismol. Res. Lett., 84(5), 810–815, doi:10.1785/0220130034.
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      • Specific References

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