Earthquake Report: M 7.8 in Turkey/Syria

We just had a severe earthquake in south eastern Turkey, northwestern Syria. We call this the Kahramanmaraş Earthquake

https://earthquake.usgs.gov/earthquakes/eventpage/us6000jllz/executive

Well, I learned tonight (14 Feb) that these M 7.8 and M 7.5 earthquakes have been named by the Turkey Minister of the Interior. The names are the Pazarcik (M7.7) and Elbistan (M7.5) earthquakes.

This earthquake is the largest magnitude event in Turkey since 1939 and it looks like there will be many many casualties.

Hopefully international aid can rapidly travel there to assist in rescue and recovery. The videos I have seen so far are terrifying.

This is the same magnitude as the 1906 San Francisco earthquake.

There has already been an aftershock with a magnitude M 6.7. This size of an earthquake would be damaging on its own, let alone as it is an aftershock.

I will be updating this page over the next few days.

UPDATE 6 Feb ’23

The East Anatolia fault is a left-lateral strike-slip fault system composed of many faults and is subdivided into different branches and different segments.

The first thing to remember is that people created these names and organized these faults using these names. The faults don’t know this and don’t care. It is possible that the people that organized these faults did not fully understand the reason these faults are here, so they may have organized them incorrectly. It may be centuries to millenia before we really know the real answer to why faults are where they are and how they relate to each other.

The Arabia plate moves north towards the Eurasia plate, forming the Alpide belt (perhaps the longest convergent plate boundary on Earth, extending from Australia/Indonesia in the east to offshore Portugal in the west. This convergence helps form the European Alps and the Asian Himalaya. In the aftershock poster below, we see the Bitlis-Zagros fold and thrust belt, also part of this convergence.

Turkey is escaping this convergence westwards. This escape has developed the right-lateral strike-slip North Anatolia fault system along the northern boundary of Turkey and the left-lateral East Anatolia fault system in southern Turkey.

During the 20th century, there was a series of large, deadly, and damaging earthquakes along the North Anatolia fault (NAF), culminating (for now) with the 1999 M7.6 Izmit Earthquake. The remaining segment of the NAF that has yet to rupture in this series is the section of the NAF that extends near Istanbul and into the Marmara Sea.

The East Anatolia fault (EAF) has a long history of large earthquakes and I include maps that show this history in the posters and in the report below (I have more to add later this week).

Today, I woke up to learn that there was a magnitude M 7.5 earthquake that happened since I posted this report the night before. This was not an aftershock but a newly triggered earthquake on a different fault than that that slipped during the M 7.8. However, there will be some people who will call this an aftershock.

https://earthquake.usgs.gov/earthquakes/eventpage/us6000jlqa/executive

The aftershocks have been filling in to reveal what faults are involved and there are many faults involved in this sequence. I include a larger scale view of these faults in the updated aftershock interpretive poster below. >>>

This M 7.5 earthquake is on a different fault than the main part of the sequence (the Çardak fault). The main sequence appears to be on two segments of the main branch of the East Anatolia fault

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 1922-2022 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 of the same figures are located in different places on the larger scale map below.

  • In the upper right corner is a map from Armijo et al. (1999) that shows the plate boundary faults and tectonic plates in the region. This M 6.7 earthquake, denoted by the blue star, is along the East Anatolia fault, a left-lateral strike-slip plate boundary fault.
  • In the upper left corner is a comparison of the shaking intensity modeled by the USGS and the shaking intensity based on peoples’ “boots on the ground” observations. People felt intensities exceeding MMI 7.
  • To the right of the intensity map is a figure from Duman and Emre (2013). This shows the historic earthquakes along the EAF.
  • In the lower right corner is a map that shows the faults in the region. Note how the topography reflects the tectonics.
  • In the lower center lerft is a plot that shows how the shaking intensity models and reports relate to each other. The horizontal axis is distance from the earthquake and the vertical axis is shaking intensity (using the MMI scale, just like in the map to the right: these are the same datasets).
  • Here is the map with a month’s seismicity plotted.


  • Here is the map with a day’s seismicity plotted (prepared a few hours after the main shock).
  • There are some additional inset figures here:
    • The USGS Finite Fault Model (FFM) is shown on center right. This graphic shows how much the USGS model suggests that the fault slipped during this earthquake. Learn more about the USGS Finite Fault Models here.
    • To the right of the legend are two maps that show (left) liquefaction susceptibility and (right) landslide probability. These are based on empirical models from the USGS that show the chance an area may have experienced these processes that may have happened as a result of the ground shaking from the earthquake. I spend more time explaining these types of models and what they represent in this Earthquake Report for the recent event in Albania.
    • I include a plot of the tide gage data from Erdemli.


    UPDATE: 6 February 2023

    • Here is the map with about a day’s seismicity plotted.
    • I plot the 2023 earthquakes in blue and the 2020 earthquakes in green.


    UPDATE: 8 February 2023

  • Here is the same two maps with about 3 day’s seismicity plotted. There are other modest changes.



    • UPDATE: 14 February 2023

    I updated some of the content below including slip rate estimates, probabilistic seismic hazard assessment for the EAF, stress modeling following the 2020 M 6.7 earthquake, and information about the Dead Sea fault.

    UPDATE: 15 February 2023

  • I updated the aftershock map that now includes about 2 weeks of aftershocks from CSEM-EMSC.
  • This also includes the faults mapped by the USGS (Reitman et a., 2023).


  • Below I also added a comparison of the USGS ground failure and intensity data between the ’20 M 6.7 and the ’22 M 7.5 & M 7.8 earthquakes.

    • UPDATE: 27 February 2023

  • I updated the aftershock map that now includes about 3 weeks of aftershocks from CSEM-EMSC.
  • This also includes the faults mapped by the USGS (Reitman et a., 2023).
  • The USGS does not have a mechanism for the M 6.7, so I am using the INGV focal mechanism from here: https://www.emsc-csem.org/Earthquake/earthquake.php?id=1218449


    Some Relevant Discussion and Figures

    • This is the plate tectonic map from Armijo et al., 1999.


      • Tectonic setting of continental extrusion in eastern Mediterranean. Anatolia-Aegean block escapes westward from Arabia-Eurasia collision zone, toward Hellenic subduction zone. Current motion relative to Eurasia (GPS [Global Positioning System] and SLR [Satellite Laser Ranging] velocity vectors, in mm/yr, from Reilinger et al., 1997). In Aegean, two deformation regimes are superimposed (Armijo et al., 1996): widespread, slow extension starting earlier (orange stripes, white diverging arrows), and more localized, fast transtension associated with later, westward propagation of North Anatolian fault (NAF). EAF—East Anatolian fault, K—Karliova triple junction, DSF—Dead Sea fault,NAT—North Aegean Trough, CR—Corinth Rift.Box outlines Marmara pull-apart region, where North Anatolian fault enters Aegean.

    • Here is the tectonic map from Dilek and Sandvol (2009).


      • Tectonic map of the Aegean and eastern Mediterranean region showing the main plate boundaries, major suture zones, fault systems and tectonic units. Thick, white arrows depict the direction and magnitude (mm a21) of plate convergence; grey arrows mark the direction of extension (Miocene–Recent). Orange and purple delineate Eurasian and African plate affinities, respectively. Key to lettering: BF, Burdur fault; CACC, Central Anatolian Crystalline Complex; DKF, Datc¸a–Kale fault (part of the SW Anatolian Shear Zone); EAFZ, East Anatolian fault zone; EF, Ecemis fault; EKP, Erzurum–Kars Plateau; IASZ, Izmir–Ankara suture zone; IPS, Intra–Pontide suture zone; ITS, Inner–Tauride suture; KF, Kefalonia fault; KOTJ, Karliova triple junction; MM, Menderes massif; MS, Marmara Sea; MTR, Maras triple junction; NAFZ, North Anatolian fault zone; OF, Ovacik fault; PSF, Pampak–Sevan fault; TF, Tutak fault; TGF, Tuzgo¨lu¨ fault; TIP, Turkish–Iranian plateau (modified from Dilek 2006).

    • This is the Woudloper (2009) tectonic map of the Mediterranean Sea. The yellow/orange band represents the Alpide Belt, a convergent plate boundary that extends from western Europe, through the Middle East, beneath northern India and Nepal (forming the Himalayas), through Indonesia, terminating east of Australia.


      •

    • Below is a series of figures from Jolivet et al. (2013). These show various data sets and analyses for Greece and Turkey.
    • Upper Panel (A): This is a tectonic map showing the major faults and geologic terranes in the region. The fault possibly associated with today’s earthquake is labeled “Neo Tethys Suture” on the map, for the Eastern Anatolia fault.
    • Lower Panel (B): This shows historic seismicity for the region. Note the general correlation with the faults in the upper panel.


      • A: Tectonic map of the Aegean and Anatolian region showing the main active structures
      (black lines), the main sutures zones (thick violet or blue lines), the main thrusts in the Hellenides where they have not been reworked by later extension (thin blue lines), the North Cycladic Detachment (NCDS, in red) and its extension in the Simav Detachment (SD), the main metamorphic units and their contacts; AlW: Almyropotamos window; BD: Bey Daglari; CB: Cycladic Basement; CBBT: Cycladic Basement basal thrust; CBS: Cycladic Blueschists; CHSZ: Central Hellenic Shear Zone; CR: Corinth Rift; CRMC: Central Rhodope Metamorphic Complex; GT: Gavrovo–Tripolitza Nappe; KD: Kazdag dome; KeD: Kerdylion Detachment; KKD: Kesebir–Kardamos dome; KT: Kephalonia Transform Fault; LN: Lycian Nappes; LNBT: Lycian Nappes Basal Thrust; MCC: Metamorphic Core Complex; MG: Menderes Grabens; NAT: North Aegean Trough; NCDS: North Cycladic Detachment System; NSZ: Nestos Shear Zone; OlW: Olympos Window; OsW: Ossa Window; OSZ: Ören Shear Zone; Pel.: Peloponnese; ÖU: Ören Unit; PQN: Phyllite–Quartzite Nappe; SiD: Simav Detachment; SRCC: South Rhodope Core Complex; StD: Strymon Detachment; WCDS: West Cycladic Detachment System; ZD: Zaroukla Detachment. B: Seismicity. Earthquakes are taken from the USGS-NEIC database. Colour of symbols gives the depth (blue for shallow depths) and size gives the magnitude (from 4.5 to 7.6).

    • Upper Panel (C): These red arrows are Global Positioning System (GPS) velocity vectors. The velocity scale vector is in the lower left corner. The main geodetic (study of plate motions and deformation of the earth) signal here is the westward motion of the North Anatolian fault system as it rotates southward as it traverses Greece. The motion trends almost south near the island of Crete, which is perpendicular to the subduction zone.
    • Lower Panel (D): This map shows the region of mid-Cenozoic (Oligo-Miocene) extension (shaded orange). It just happens that there is still extension going on in parts of this prehistoric extension.


      • C: GPS velocity field with a fixed Eurasia after Reilinger et al. (2010) D: the domain affected by distributed post-orogenic extension in the Oligocene and the Miocene and the stretching lineations in the exhumed metamorphic complexes.

    • Upper Panel (E): This map shows where the downgoing slab may be located (in blue), along with the volcanic centers associated with the subduction zone in the past.
    • Lower Panel (F): This map shows the orientation of how seismic waves orient themselves differently in different places (anisotropy). We think seismic waves travel in ways that reflects how tectonic strain is stored in the earth. The blue lines show the direction of extension in the asthenosphere, green lines in the lithospheric mantle, and red lines for the crust.


      • E: The thick blue lines illustrate the schematized position of the slab at ~150 km according to the tomographic model of Piromallo and Morelli (2003), and show the disruption of the slab at three positions and possible ages of these tears discussed in the text. Velocity anomalies are displayed in percentages with respect to the reference model sp6 (Morelli and Dziewonski, 1993). Coloured symbols represent the volcanic centres between 0 and 3 Ma after Pe-Piper and Piper (2006). F: Seismic anisotropy obtained from SKS waves (blue bars, Paul et al., 2010) and Rayleigh waves (green and orange bars, Endrun et al., 2011). See also Sandvol et al. (2003). Blue lines show the direction of stretching in the asthenosphere, green bars represent the stretching in the lithospheric mantle and orange bars in the lower crust.

    • Upper Panel (G): This is the map showing focal mechanisms in the poster above. Note the strike slip earthquakes associated with the North Anatolia and East Anatolia faults and the thrust/reverse mechanisms associated with the thrust faults.


      • G: Focal mechanisms of earthquakes over the Aegean Anatolian region.

    • Here are some interesting seismicity plots from Bulut et al., 2012.
    • The upper two panels show the faults, earthquake epicenters, depth profile locations, and the names of the EAF fault segments.
    • The lower panels show the seismicity plotted relative to depth, for each of the 5 profiles.


      • Epicentral map and depth sectional views for seismicity along the EAFZ obtained in this study based on (a, c) absolute locations and (b, d) double-difference derived relative locations, respectively. Black dots represent earthquake locations and the gray lines are presently active faults. Selected NWSE trending transects indicated in Figures 6a and 6b and plotted as depth sections in Figures 6c and 6d.

    Fault Mapping

    • Here is a map showing tectonic domains (Taymaz et al., 2007).


      • Schematic map of the principal tectonic settings in the Eastern Mediterranean. Hatching shows areas of coherent motion and zones of distributed deformation. Large arrows designate generalized regional motion (in mm a21) and errors (recompiled after McClusky et al. (2000, 2003). NAF, North Anatolian Fault; EAF, East Anatolian Fault; DSF, Dead Sea Fault; NEAF, North East Anatolian Fault; EPF, Ezinepazarı Fault; CTF, Cephalonia Transform Fault; PTF, Paphos Transform Fault.

    • Here is a tectonic overview figure from Duman and Emre, 2013.


      • The main fault systems of the AN–AR and TR–AF plate boundaries (modified from Sengor & Yılmaz 1981; Saroglu et al. 1992a, b; Westaway 2003; Emre et al. 2011a, b, c). Arrows indicate relative plate motions (McClusky et al. 2000). Abbreviations: AN, Anatolian microplate; AF, African plate; AR, Arabian plate; EU, Eurasian plate; NAFZ, North Anatolian Fault Zone; EAFZ, East Anatolian Fault Zone; DSFZ, Dead Sea Fault Zone; MF; Malatya Fault, TF, Tuzgo¨lu¨ fault; EF, Ecemis¸ fault; SATZ, Southeast Anatolian Thrust Zone; SS, southern strand of the EAFZ; NS, northern strand of the EAFZ.

    • This is a map that shows the subdivisions of the EAF (Duman and Emre, 2013). Note Lake Hazar for reference.


      • Map of the East Anatolian strike-slip fault system showing strands, segments and fault jogs. Abbreviations: FS, fault Segment; RB, releasing bend; RS, releasing stepover; RDB, restraining double bend; RSB, restraining bend; PB, paired bend; (1) Du¨zic¸i–Osmaniye fault segment; (2) Erzin fault segment; (3) Payas fault segment; (4) Yakapınar fault segment; (5) C¸ okak fault segment; (6) Islahiye releasing bend; (7) Demrek restraining stepover; (8) Engizek fault zone; (9) Maras¸ fault zone.

    • This map shows the fault mapping from Duman and Emre, 2013. Note Lake Hazar for reference. We can see some of the thrust faults mapped as part of the Southeast Anatolia fault zone.


      • Map of the (a) Palu and (b) Puturge segments of the East Anatolian fault. Abbreviations: LHRB, Lake Hazar releasing bend; PS, Palu segment; ES, Erkenek segment; H, hill; M, mountain; C, creek; (1) left lateral strike-slip fault; (2) normal fault; (3) reverse or thrust fault; (4) East Anatolian Fault; (5) Southeastern Anatolian Thrust Zone; (6) syncline;(7) anticline; (8) undifferentiated Holocene deposits; (9) undifferentiated Quaternary deposits; (10) landslide.

    • This is the figure from Duman and Emre (2013) that shows the spatial extent for historic earthquakes on the EAF.


      • Surface ruptures produced by large earthquakes during the 19th and 20th centuries along the EAF. Data from Arpat (1971), Arpat and S¸arog˘lu (1972), Seymen and Aydın (1972), Ambraseys (1988), Ambraseys and Jackson (1998), Cetin et al. (2003), Herece (2008), Karabacak et al. (2011) and this study. Ruptured fault segments are highlighted.

    Slip Rates

    • Aktug et al. (2016) used GPS observations to evaluate the plate motion rates along the EAF.
    • The following two figures show the plate motion vectors and profiles of the plate velocities across the fault zone in three locations (a, b, and c).
    • They used GPS data from different studies, which is the reason the vectors have different colors.


      • The GPS observations employed in this study. The velocity error ellipses are at 95% confidence level. The dashed rectangles show the profiles for investigating the trade-off between the slip rate and the locking depth.

    • These are the 3 GPS velocity profiles from Aktug et al. (2016) shown on the above map.
    • The panels on the left represent their estimates for the slip rate of the EAF relative to the locking depth for the EAF.
    • The panels on the right show how the GPS velocities change across the fault zone in these 3 areas. The velocities are measured parallel to the fault.
    • Using profile a as an example, on the ight side of the fault, the velocity is held to be about 0 mm per year. As we cross the fault, the velocity jumps up to about 10 mm/year. So, the slip rate of the EAF zone across the profiles a, b, and c are about 10, 7, and 12 mm/year. As a reference, the San Andreas fault in California has a slip rate of about 25 mm/year.


      • The variability of the slip rates w.r.t. the locking depth (red) and the χ2 values of the estimation (black). The thick grey bands show 2-s error bounds of the slip rates for profiles a to c (left panel) and the velocity profiles with slip rate and locking depth estimated simultaneously (right panel). The red curve shows the model fit to the GPS data (open circles with error bars at 95% confidence level) and the blue curve is the fault parallel shear strain rate for the best fit model determined from the analysis shown in Figure 3 and described in the text.

    • Ferry et al. (2011) used a 14,000 year long record of prehistoric earthquakes to evaluate the episodic behavior of the Dead Sea fault (DSF).
    • This first map show the DSF, GPS site velocities, and geological slip rates in different locations. The DSF eventually turns into the EAF.


      • a) General map of the Dead Sea Transform system. Numbers are geological slip rates (in black) and geodetic strain rates (in white). Sources: Klinger et al. (2000); Niemi et al. (2001); Meghraoui et al. (2003); Reilinger et al. (2006); Ferry et al. (2007). Pull-apart basins: ab, Amik basin; gb, Ghab basin; hb, Hula basin; ds, Dead Sea. Major fault segments: EAF, East Anatolian fault; AF, Afrin fault; KF, Karasu fault; JSF, Jisr Shuggur fault; MF, Missyaf fault; YF, Yammouneh fault; ROF, Roum fault; RAF, Rachaya fault; SF, Serghaya fault; JVF, Jordan Valley fault; WAF, Wadi Araba fault. (b) Detailed map of the JVF segment between the Sea of Galilee and the Dead Sea. The segment itself is organized as six 15-km to 30-km-long right-stepping subsegments limited by 2-km to 3-km-wide transpressive relay zones. The active trace of the JVF continues for a further ∼10 km northward into the Sea of Galilee (SG) and ∼20 km southward into the northern Dead Sea (DS). The color version of this figure is available only in the electronic edition.

    • This map (Ferry et al., 2011) shows the historic seismicity for this region with earthquake mechanisms for some of the earthquakes.


      • Seismicity of the Dead Sea Transform system. Instrumental events with M ≥4 from 1964 to 2006 (IRIS Data Management Center; see Data and Resources section) in filled circles. Background seismicity is very scarce and mainly restricted to the Lebanese Bend and the Jordan Valley. The 1995 Mw 7.3 Aqaba earthquake and aftershock swarm dominate the seismicity of the Red Sea basin. Historical events with I0 ≥ VII (Ambraseys and Jackson, 1998; Sbeinati et al., 2005) in open circles. Apart from the 1927 Mw 6.2 Jericho earthquake, no significant event has occurred along the JVF since A.D. 1033 (see text for details).

    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 addition to what I write below, the data on the left are from the M 7.5 and the data on the right are from the M 7.8.
    • 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 orange line, or neither line. What reasons can you think that may be explain these real observation deviations from the models.
    • Below 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).


    • Here is a comparison between these three earthquakes from 2020 and 2022.
    • The scale and spatial extent for each map is the same.


      Earthquake Triggered Landslides

    • 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.


    • Here is an excellent educational video from IRIS and a variety of organizations. The video helps us learn about how earthquake intensity gets smaller with distance from an earthquake. The concept of liquefaction is reviewed and we learn how different types of bedrock and underlying earth materials can affect the severity of ground shaking in a given location. The intensity map above is based on a model that relates intensity with distance to the earthquake, but does not incorporate changes in material properties as the video below mentions is an important factor that can increase intensity in places.

    • If we look at the map at the top of this report, we might imagine that because the areas close to the fault shake more strongly, there may be more landslides in those areas. This is probably true at first order, but the variation in material properties and water content also control where landslides might occur.
    • There are landslide slope stability and liquefaction susceptibility models based on empirical data from past earthquakes. The USGS has recently incorporated these types of analyses into their earthquake event pages. More about these USGS models can be found on this page.
    • Below is a figure that shows both landslide probability and liquefaction susceptibility maps for this M 7.8 earthquake.


    • Below is a figure that compares both landslide probability and liquefaction susceptibility maps for these three earthquakes.
    • The scale for each map is the same.


    Fault Scaling Relations

  • There is a seminal paper (Wells and Coppersmith, 1994) where these geologists compiled the existing data from global earthquakes.
  • They extracted different aspects of the physical size of these earthquakes so that they could develop relations between the earthquake size (e.g., length of the fault that ruptured the surface of the Earth) and earthquake magnitude. Since these relations are based on real data from real earthquakes, we call these empirical scaling relations (i.e., the size of the earthquake slip “scales” with the size of the magnitude).
  • Their analyses also subdivided the earthquakes in ways to see if different types of earthquakes (strike-slip, normal, or thrust/reverse) had different scaling relations.
  • Some have updated the database of earthquake observations. However, these updated scaling relations are not that much different than the original Wells and Coppersmith (1994) scaling relations. Perhaps there is sufficient variation in earthquake size that we have yet to deconvolve all the variation in fault ruptures?
  • Below I present the Wells and Coppersmith (1994) scaling relations for subsurface earthquake slip length. I do this because it may be a while until we have a good estimate for other measures (like surface rupture length) but we can estimate the subsurface fault length in different ways with existing data (like the spatial extent of aftershocks).
  • In the upper panel I list the rough length of three fault segments that are part of the East Anatolia fault system.
  • I use the relations represented by the diagonal lines in the center panel to calculate the earthquake magnitude for faults of varying length (100-200km). Based on their relations, a magnitude M 7.8 earthquake may have ruptured a fault with a subsurface length of 200 km.


Seismic Hazard and Seismic Risk

  • These are the two seismic maps from the Global Earthquake Model (GEM) project, the GEM Seismic Hazard and the GEM Seismic Risk maps from Pagani et al. (2018) and Silva et al. (2018).

    • The GEM Seismic Hazard Map:


    • The Global Earthquake Model (GEM) Global Seismic Hazard Map (version 2018.1) depicts the geographic distribution of the Peak Ground Acceleration (PGA) with a 10% probability of being exceeded in 50 years, computed for reference rock conditions (shear wave velocity, VS30, of 760-800 m/s). The map was created by collating maps computed using national and regional probabilistic seismic hazard models developed by various institutions and projects, and by GEM Foundation scientists. The OpenQuake engine, an open-source seismic hazard and risk calculation software developed principally by the GEM Foundation, was used to calculate the hazard values. A smoothing methodology was applied to homogenise hazard values along the model borders. The map is based on a database of hazard models described using the OpenQuake engine data format (NRML). Due to possible model limitations, regions portrayed with low hazard may still experience potentially damaging earthquakes.
    • Here is a view of the GEM seismic hazard map for Europe.


      •

    • The USGS Seismic Hazard Map:

    • Here is a map that displays an estimate of seismic hazard for the region (Jenkins et al., 2010). This comes from Giardini et al. (1999).


      • The Global Seismic Hazard Map. Peak ground acceleration (pga) with a 10% chance of exceedance in 50 years is depicted in m/s2. The site classification is rock everywhere except Canada and the United States, which assume rock/firm soil site classifications. White and green correspond to low seismicity hazard (0%-8%g), yellow and orange correspond to moderate seismic hazard (8%-24%g), pink and dark pink correspond to high seismicity hazard (24%-40%g), and red and brown correspond to very high seismic hazard (greater than 40%g).

    • The GEM Seismic Risk Map:


    • The Global Seismic Risk Map (v2018.1) presents the geographic distribution of average annual loss (USD) normalised by the average construction costs of the respective country (USD/m2) due to ground shaking in the residential, commercial and industrial building stock, considering contents, structural and non-structural components. The normalised metric allows a direct comparison of the risk between countries with widely different construction costs. It does not consider the effects of tsunamis, liquefaction, landslides, and fires following earthquakes. The loss estimates are from direct physical damage to buildings due to shaking, and thus damage to infrastructure or indirect losses due to business interruption are not included. The average annual losses are presented on a hexagonal grid, with a spacing of 0.30 x 0.34 decimal degrees (approximately 1,000 km2 at the equator). The average annual losses were computed using the event-based calculator of the OpenQuake engine, an open-source software for seismic hazard and risk analysis developed by the GEM Foundation. The seismic hazard, exposure and vulnerability models employed in these calculations were provided by national institutions, or developed within the scope of regional programs or bilateral collaborations.
    • Here is a view of the GEM seismic risk map for Europe.


      •

    • Probabilistic Seismic Hazard Assessment – East Anatolia fault

    • Gülerce et al. (2017) conducted a Probabilistic Seismic Hazard Assessment (PSHA) for the EAF. I hope you are keeping up with all the acronyms in this report.
    • A PSHA is basically a way of taking information about earthquake recurrence (from paleoseismology, seismicity rates, geodesy, etc.) for faults in a given region and using this information to make estimates of the likelihood (the chance) of a certain measure of ground shaking that might be exceeded over a period of time.
    • The California Geological Survey has a website that provides an overview of what PSHA is and how it is conducted.
    • A key part of PSHA is the incorporation of all possible and probable earthquakes for the faults in the analysis region. People conducting PSHA use a “logic tree” to organize this variation. Each branch of the logic tree is given a weight that the experts think that that branch is most likely to happen.
    • Here is the logic tree presented by Gülerce et al. (2017).


    • Of the many products that can come from a PSHA, the principal output are a series of maps that show the chance that ground shaking levels will be exceeded. E.g., a map that shows a 10% chance of being exceeded in 50 years (in other words, the chance that this ground shaking might happen in 475 years; aka the 475 year return period ground shaking map).
    • There are lots of parameters that we use to calculate the ground shaking, such as the seismic velocity structure of the Earth (e.g., the Vs30, the seismic velocity of the upper 30 meters of the Earth).
    • Here is the table showing the fault parameters for the faults used in this PSHA.


    • These first maps are the 475 year return period maps (10% in 50 years) for Vs30 = 760 m/second (“softer” rock) and Vs30 = 1100 m/second (“harder” rock).


      • PSHA map for the 475-yr return period peak ground acceleration (PGA) for (a) VS30  760 m=s and (b) VS30  1100 m=s. Contour lines (for PGA  0:4g) represent the design value for the highest earthquake zone in Turkish Earthquake Code (2007). The color version of this figure is available only in the electronic edition.

    • These maps are the 2475 year return period maps (2% in 50 years) for Vs30 = 760 m/second (“softer” rock) and Vs30 = 1100 m/second (“harder” rock).


      • PSHA map for the 2475-yr return period PGA for (a) VS30  760 m=s and (b) VS30  1100 m=s. Contour lines (for PGA  0:6g) represent the design value for special structures for the highest earthquake zone in Turkish Earthquake Code (2007). The color version of this figure is available only in the electronic edition.

    Stress Triggering

  • 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.”
  • Lin et al. (2020) used the 24 January 2020 M 6.7 Doganyol Earthquake to investigate how the EAF slips before and after the M 6.7 mainshock.
  • They also modeled the static coulomb stress changes along the EAF system following the 2020 M 6.7 earthquake.
  • This map shows historic earthquakes and mechanisms, highlighting the 2020 M 6.7 event in red. (Lin et al., 2020).


    • Tectonic setting of the 2020 Doganyol earthquake. Red and black stars represent the epicenter of the 2020 earthquake and historical earthquakes, respectively. Black lines indicate the major active faults in this region, and the white box shows the projection of the fault plane. The locations of mainshock and historical earthquakes are from Kandilli Observatory and Earthquake Research Institute (KOERI; see Data and Resources) and U.S. Geological Survey (USGS) (see Data and Resources), respectively. Focal mechanisms are also plotted (see Data and Resources). The inset
    shows motions of major tectonic units (Armijo et al., 1999).

  • This map shows the extent for some historic earthquakes and the inset shows the change in static coulomb stress on the EAF following the 2020 M 6.7 event.


    • Segments of the East Anatolian fault (EAF), distribution of historical earthquakes, and stress accumulation on the surrounding faults caused by the earthquake at a depth of 10 km (inset). The receiver fault is −246°=67°= − 9°. The geometry of each fault segment refers to the mechanism of the regional historical earthquake, and the effective friction coefficient is 0.4. The locations of historical earthquakes are from Ambraseys (1989), Ambraseys and Jackson (1998), Tan et al. (2008), and USGS (see Data and Resources). GCMT; Global Centroid Moment Tensor; KTJ, Karliova Triple Junction.

  • Here are a suite of static coulomb stress changes given a range of fault parameters.


    • Stress accumulation caused by the earthquake on the surrounding faults calculated at a depth of 10 km; the dip angles are (a) 67°, (b) 47°, and (c) 87° with reference strikes fromDuman and Emre (2013). Stress accumulation caused by the earthquake on the surrounding faults calculated at (d) depths of 5 km; the geometry of each fault segment refers to the mechanism of the regional historical earthquake. The effective friction coefficient is 0.4.

  • Dr. Shinji Toda worked with Ross Stein and others to calculate static coulomb stress changes related to the M 7.8 earthquake. Here is their article and below is a video from their report.

    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.
  • 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

    • Specific References

  • Aktug, B., Ozener, H., Dogru, A., Sabuncu, A., Turgut, B., Halicioglu, K., Yilmaz, O., Havazli, E.,Slip rates and seismic potential on the East Anatolian Fault System using an improved GPS velocity field, Journal of Geodynamics (2016), http://dx.doi.org/10.1016/j.jog.2016.01.001
  • Armijo, R., Meyer, B., Hubert, A., and Barka, A., 1999. Westward propagation of the North Anatolian fault into the northern Aegean: Timing and kinematics in Geology, v. 27, no. 3, p. 267-270
  • Basili R., G. Valensise, P. Vannoli, P. Burrato, U. Fracassi, S. Mariano, M.M. Tiberti, E. Boschi (2008), The Database of Individual Seismogenic Sources (DISS), version 3: summarizing 20 years of research on Italy’s earthquake geology, Tectonophysics, doi:10.1016/j.tecto.2007.04.014
  • Brun, J.-P., Sokoutis, D., 2012. 45 m.y. of Aegean crust and mantle flow driven by trench retreat. Geol. Soc. Am., v. 38, p. 815–818.
  • Bulut, F., M. Bohnhoff, T. Eken, C. Janssen, T. Kılıç, and G. Dresen (2012), The East Anatolian Fault Zone: Seismotectonic setting and spatiotemporal characteristics of seismicity based on precise earthquake locations, J. Geophys. Res., 117, B07304, http://dx.doi.org/10.1029/2011JB008966.
  • Caputo, R., Chatzipetros, A., Pavlides, S., and Sboras, S., 2012. The Greek Database of Seismogenic Sources (GreDaSS): state-of-the-art for northern Greece in Annals of Geophysics, v. 55, no. 5, doi: 10.4401/ag-5168
  • Dilek, Y., 2006. Collision tectonics of the Mediterranean region: Causes and consequences in Dilek, Y., and Pavlides, S., eds., Postcollisional tectonics and magmatism in the Mediterranean region and Asia: Geological Society of America Special Paper 409, p. 1–13
  • Dilek, Y. and Sandvol, E., 2006. Collision tectonics of the Mediterranean region: Causes and consequences in Dilek, Y., and Pavlides, S., eds., Postcollisional tectonics and magmatism in the Mediterranean region and Asia: Geological Society of America Special Paper 409, p. 1–13
  • DISS Working Group (2015). Database of Individual Seismogenic Sources (DISS), Version 3.2.0: A compilation of potential sources for earthquakes larger than M 5.5 in Italy and surrounding areas. http://diss.rm.ingv.it/diss/, Istituto Nazionale di Geofisica e Vulcanologia; DOI:10.6092/INGV.IT-DISS3.2.0.
  • Duman, T.Y. and Emre, O., 2013. The East Anatolian Fault: geometry, segmentation and jog characteristics in Geological Society of London, Special Publications, v. 372, doi: 10.1144/SP372.14
  • Ersoy, E.Y., Cemen, I., Helvaci, C., and Billor, Z., 2014. Tectono-stratigraphy of the Neogene basins in Western Turkey: Implications for tectonic evolution of the Aegean Extended Region in Tectonophysics v. 635, p. 33-58.
  • Ferry, M., Meghraoui, M., Karaki, N.A., Al-Taj, M., Khalil, L., 2011. Episodic Behavior of the Jordan Valley Section of the Dead Sea Fault Inferred from a 14-ka-Long Integrated Catalog of Large Earthquakes in bSSA, v. 101, no. 1., p. 39-67, https://doi.org/10.1785/0120100097
  • Gülerce, Z., Shah, S.T., Menekşe, A, Menekşe, A.A., Kaymakci, N., and Çetin, K.Ö., 2017. Probabilistic Seismic‐Hazard Assessment for East Anatolian Fault Zone Using Planar Fault Source Models in BSSA, v. 107, no. 5, p. 2353-2366, https://doi.org/10.1785/0120170009
  • Jenkins, Jennifer, Turner, Bethan, Turner, Rebecca, Hayes, G.P., Sinclair, Alison, Davies, Sian, Parker, A.L., Dart, R.L., Tarr, A.C., Villaseñor, Antonio, and Benz, H.M., compilers, 2013, Seismicity of the Earth 1900–2010 Middle East and vicinity (ver 1.1, Jan. 28, 2014): U.S. Geological Survey Open-File Report 2010–1083-K, scale 1:7,000,000, https://pubs.usgs.gov/of/2010/1083/k/.
  • Jolivet, L., et al., 2013. Aegean tectonics: Strain localisation, slab tearing and trench retreat in Tectonophysics, v. 597-598, p. 1-33
  • Kokkalas, S., et al., 2006. Postcollisional contractional and extensional deformation in the Aegean region in GSA Special Papers, v. 409, p. 97-123.
  • Kurt, H., Demirbag, E., and Kuscu, I., 1999. Investigation of the submarine active tectonism in the Gulf of Gokova, southwest Anatolia–southeast Aegean Sea, by multi-channel seismic reflection data in Tectonophysics, v. 305, p. 477-496
  • Lin, X., J. Hao, D.Wang, R. Chu, X. Zeng, J. Xie, B. Zhang, and Q. Bai (2020). Coseismic Slip Distribution of the 24 January 2020 Mw 6.7 Doganyol Earthquake and in Relation to the Foreshock and Aftershock Activities, Seismol. Res. Lett. 92, 127–139, https://doi.org/10.1785/0220200152
  • Papazachos, B.C., Papadimitrious, E.E., Kiratzi, A.A., Papazachos, C.B., and Louvari, E.k., 1998. Fault Plane Solutions in the Aegean Sea and the Surrounding Area and their Tectonic Implication, in Bollettino Di Geofisica Terorica Ed Applicata, v. 39, no. 3, p. 199-218.
  • Reitman, Nadine G, Richard W. Briggs, William D. Barnhart, Jessica A. Thompson Jobe, Christopher B. DuRoss, Alexandra E. Hatem, Ryan D. Gold, and John D. Mejstrik (2023) Preliminary fault rupture mapping of the 2023 M7.8 and M7.5 Türkiye Earthquakes. https://doi.org/10.5066/P985I7U2
  • Taymaz, T., Yilmaz, Y., and Dilek, Y., 2007. The geodynamics of the Aegean and Anatolia: introduction in Geological Society Special Publications, v. 291, p. 1-16.
  • Toda, S., Stein, R. S., Özbakir, A. D., Gonzalez-Huizar, H., Sevilgen, V., Lotto, G., and Sevilgen, S., 2023, Stress change calculations provide clues to aftershocks in 2023 Türkiye earthquakes, Temblor, http://doi.org/10.32858/temblor.295
  • Wouldloper, 2009. Tectonic map of southern Europe and the Middle East, showing tectonic structures of the western Alpide mountain belt. Only Alpine (tertiary) structures are shown.

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