Earthquake Report: Iraq

A month and a half ago, I was attending the PATA conference and an earthquake hit Iran and Iraq the night before our first field trip. Thus, I did not have the time to address this earthquake at the time. I am preparing this report in support of my annual summary.

This was a damaging earthquake and is the most deadly for 2017. Over 500 people were killed and thousands were injured.

I post lots of material below that was developed in the 6 weeks following the earthquake.

Below is my interpretive poster for this earthquake.

I plot the seismicity from the past month, with color representing depth and diameter representing magnitude (see legend). I include earthquake epicenters from 1917-2017 with magnitudes M > 6.5.
I plot the USGS fault plane solutions (moment tensors in blue) for the M 7.3 earthquake.

  • I placed a moment tensor / focal mechanism legend on the poster. There is more material from the USGS web sites about moment tensors and focal mechanisms (the beach ball symbols). Both moment tensors and focal mechanisms are solutions to seismologic data that reveal two possible interpretations for fault orientation and sense of motion. One must use other information, like the regional tectonics, to interpret which of the two possibilities is more likely. Based upon the tectonics associated with the San Andreas and Maacama faults, I interpret this M 4.3 earthquake to be a right-lateral strike-slip fault.
  • I also include the shaking intensity contours on the map. These use the Modified Mercalli Intensity Scale (MMI; see the legend on the map). This is based upon a computer model estimate of ground motions, different from the “Did You Feel It?” estimate of ground motions that is actually based on real observations. The MMI is a qualitative measure of shaking intensity. More on the MMI scale can be found here and here. This is based upon a computer model estimate of ground motions, different from the “Did You Feel It?” estimate of ground motions that is actually based on real observations.

Here are the USGS pages for the main earthquake in this sequence.

I include some inset figures.

  • In the lower right corner I include a map that shows the major plate boundary and major crustal faults in the region, as well as relative plate motions plotted as arrows (Taymaz et al.,
    2007). I place a green star in the general location of the M 7.3 earthquake. Note that this M 7.3 earthquake happened along the Bitis-Zagros Fold Belt.
  • In the upper right corner is a map that shows the results of interfereometric RADAR analyses as prepared by GSI in Japan. This map shows a region of subsidence to the southwest of the M 7.3 epicenter (the largest orange circle) and a region of uplift to the northeast of this M 7.3 earthquake. More about this map below.
  • To the left of this interferogram, I include a basic tectonic map of this region (Woudloper, 2009). Maps with local (larger) scale have much more detailed views of the faulting. I place a green star in the general location of this M 7.3 earthquake.
  • In the upper left corner are two maps that show how Earth’s surface moved during the earthquake (and shortly afterwards). The left panel shows east-west motion and the right panel shows up-down motion (this looks similar to the figure in the upper right corner.
  • In the lower left corner I place a map that shows the large scale details of the crustal faults in the Bitis-Zagros Fold Belt (Allen et al., 2013). I place a green star in the general location of this M 7.3 earthquake.
  • To the right of this fault map is a cross section A-A.’ The location of this cross section is designated by a blue line on the map in the lower left corner, as well as on the main interpretive poster map.


  • Here is a comparison between the “Did You Feel It?” map and the Shakemap. Both maps represent shaking intensity with the same scale, the MMI scale (described above). The DYFI map on the left is based on peoples’ observations as they report using the USGS DYFI website. The map on the right is the result of numerical simulations of shaking intensity. Below each map are regressions of those data.


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  • This map shows the plate boundary and intraplate faults of the region. Also shown are the relative plate motions as black arrows. Note how the Bitis-Zagros Fold Belt (BZFB) is a dextral oblique (right-lateral thrust) fault system. This fault system is part of the Alpide belt, which is oriented parallel to the Arabia-Anatolia relative plate motion (ergo the strike-slip motion).


    • (a) Seismicity of the Eastern Mediterranean region and surroundings reported by USGS–NEIC during 1973–2007 with magnitudes for M . 3 superimposed on a shaded relief map derived from the GTOPO-30 Global Topography Data taken after USGS. Bathymetry data are derived from GEBCO/97–BODC, provided by GEBCO (1997) and Smith & Sandwell (1997a, b). (b) Summary sketch map of the faulting and bathymetry in the Eastern Mediterranean region, compiled from our observations and those of Le Pichon & Angelier (1981), Taymaz (1990), Taymaz et al. (1990, 1991a, b); S¸arogˇlu et al. (1992), Papazachos et al. (1998), McClusky et al. (2000) and Tan & Taymaz (2006). Large black arrows show relative motions of plates with respect to Eurasia (McClusky et al. 2003). Bathymetry data are derived from GEBCO/97–BODC, provided by GEBCO (1997) and Smith & Sandwell (1997a, b). Shaded relief map derived from the GTOPO-30 Global Topography Data taken after USGS. NAF, North Anatolian Fault; EAF, East Anatolian Fault; DSF, Dead Sea Fault; NEAF, North East Anatolian Fault; EPF, Ezinepazarı Fault; PTF, Paphos Transform Fault; CTF, Cephalonia Transform Fault; PSF, Pampak–Sevan Fault; AS, Apsheron Sill; GF, Garni Fault; OF, Ovacık Fault; MT, Mus¸ Thrust Zone; TuF, Tutak Fault; TF, Tebriz Fault; KBF, Kavakbas¸ı Fault; MRF, Main Recent Fault; KF, Kagˇızman Fault; IF, Igˇdır Fault; BF, Bozova Fault; EF, Elbistan Fault; SaF, Salmas Fault; SuF, Su¨rgu¨ Fault; G, Go¨kova; BMG, Bu¨yu¨k Menderes Graben; Ge, Gediz Graben; Si, Simav Graben; BuF, Burdur Fault; BGF, Beys¸ehir Go¨lu¨ Fault; TF, Tatarlı Fault; SuF, Sultandagˇ Fault; TGF, Tuz Go¨lu¨ Fault; EcF, Ecemis¸ Fau; ErF, Erciyes Fault; DF, Deliler Fault; MF, Malatya Fault; KFZ, Karatas¸–Osmaniye Fault Zone.

  • The Alpide Belt, shown in this map, is a convergent plate boundary that extends from Australia to Portugal. This map shows the westernmost extent of this system. The convergence here drives uplift of the Himalayas and the European Alps. Subduction along the Makran and Sunda subduction zones are also part of this system.


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  • This is a great map showing some details of the tectonics associated with the Arabia plate (Stern and Johnson, 2010).


    • Simpli”ed map of the Arabian Plate, with plate boundaries, approximate plate convergence vectors, and principal geologic features. Note location of Central Arabian Magnetic Anomaly (CAMA).

  • This map (Allen et al., 2013) shows focal mechanisms (fault plane solutions) for earthquakes associated with the BZFB. GPS velocities are also plotted in blue (rates of motion at points on the earth, measured in mm per year), relative to Iran.


    • (a) Regional topography and seismicity of the Arabia-Eurasia collision. Large dots are epicenters of earthquakes of M >6 from 1900 to 2000 [Jackson, 2001], small dots are epicenters from the EHB catalogue 1964–1999, M >5. Red arrows show GPS-derived velocity with respect to Asia from Sella et al. [2002]. A= Alborz; TIP = Turkish-Iranian plateau; Z = Zagros. (b) Seismicity of the Zagros: focal mechanisms reported in Nissen et al. [2011] and references therein. Note the scarcity of thrusts above the smoothed 1250m regional elevation contour (derived using a Gaussian filter with a radius of 50 km). Earthquake epicenters are accurate to within 20 km [Nissen et al., 2011]. GPS vectors are from Walpersdorf et al. [2006]. MZRF =Main Zagros Reverse Fault (Zagros suture).

  • This map shows a detailed view of faults and folds in the BZFB (Allen et al., 2013).


    • (a) Location map and major structures of the Zagros Simply Folded Belt, Iran. Derived from NIOC [1975, 1977], Berberian [1995], Hessami et al. [2001], Blanc et al. [2003], Agard et al. [2005], and Babaie et al. [2006]. Key to fault abbreviations: B = Borazjan; Iz = Izeh; K= Kazerun; KB= Kareh Bas; Kh = Khanaqin; S = Sarvestan; SP = Sabz-Pushan; BL = Balarud Line; A= Kuh-e Asmari. b) Earthquake epicentres across the Zagros, from Nissen et al. [2011] and references therein, divided by fault type. MZRF =Main Zagros Reverse Fault.


  • This is cross section A-A’ from the map above (also on poster). Note the thrust faults and the strike-slip faults represented in this section (Allen et al., 2013). While this section is to the south of the M 7.3 earthquake, it still represents the generalized tectonics in the region (dextral oblique plate boundary).


    • (a) Cross-section through the Dezful Embayment and the Bakhtyari Culmination.

  • The Geospatial Information Authority of Japan (GSI) conducted some analyses using Synthetic Aperture Radar (SAR). “Two or more line-of-sight displacements with different observing directions can be decomposed to quasi east-west and up-down components.” They describe their interpretation below.




    • Large displacement (~90 cm upward and ~50 cm westward) has been detected around 20 km NNW of Sarpol-e Zahab. Around the epicenter, ~30 cm downward and ~35 cm westward displacement has been detected.

  • 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).

Other Social Media Posts

  • Here is a plot showing historic seismicity from Dr. Jascha Polet (Cal Poly Pomona Seismologist).

    References

  • Allen, M.B., Saville, C., Blac, E.K-P., Talebian, M., and Nissen, E., 2013. Orogenic plateau growth: Expansion of the Turkish-Iranian Plateau across the Zagros fold-and-thrust belt in Tectonics, v. 32, p. 171-190, doi:10.1002/tect.20025
  • Giardini, D., Grunthal, G., Shedlock, K., Zhang. P., and Global Seismic Hazards Program, 1999. Global seismic hazards map: Accessed on Jan. 9, 2007 at http://www.seismo.ethz.ch/GSHAP.
  • 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/.
  • Stern, R.J. and Johnson, P., 2010. Continental lithosphere of the Arabian Plate: A geologic, petrologic, and geophysical synthesis in Earth-Science Reviews, v. 101, p. 29-67.
  • Taymaz, T., Yilmaz, Y., and Dilek, Y., 2007. The geodynamics of the Aegean and Anatolia: introduction in Geological Society, London, Special Publications, v. 291; p. 1-16, doi:10.1144/SP291.1
  • Woudloper, 2009. Tectonic map of southern Europe and the Middle East, showing tectonic structures of the western Alpide mountain belt.