The 2020 M_w 6.8 Elazığ (Turkey) Earthquake Reveals Rupture Behavior of the East Anatolian Fault

Abstract

The 2020 Mw 6.8 Elazığ earthquake was the largest along the East Anatolian Fault (EAF) in over a century, providing valuable insights into its rupture behavior. We use satellite geodesy and seismology to detail the mainshock rupture, postseismic deformation, and aftershocks. The mainshock propagated mostly westward at ∼2 km/s from a nucleation point on an abrupt ∼10° fault bend. Only one end of the rupture corresponds to an established EAF segment boundary, and the earthquake may have propagated into the slip zone of the 1874 M ∼ 7.1 Gölcuk Gölu earthquake. It exhibits a pronounced (∼80%) shallow slip deficit, only a small proportion of which is recovered by early aseismic afterslip. The slow rupture velocity, shallow slip deficit, and minimal afterslip are characteristic of earthquakes hosted by faults of low‐to‐intermediate structural maturity, indicating that faults continue to evolve in important ways even as they accrue cumulative offsets of tens of kilometers.

Kinematics and Dynamics of the 24 January 2020 Mw 6.7 Elazig, Turkey Earthquake

“…We try to refine the fault geometry in order to fit better the curved fault trace but find a sharp drop of the InSAR fits, and we believe that our geometry should be an adequate, though idealized, representation of fault structure at the scale of the seismogenic zone. Furthermore, the rupture speed that fits all the data sets best is as low as 2.0 km/s (see Figure S1), consistent with what is estimated based on back projection using a teleseismic array (Pousse‐Beltran et al, 2020). The low rupture speed is usually considered as an indicator of fault immaturity, which reconfirms the EAFZ as a young strike‐slip fault (e.g., Bulut et al, 2012).…”

“…In fact, Cheloni and Akinci's (2020) fault geometry inversion using InSAR observations also favors one single fault plane. Besides, both the models of Cheloni and Akinci (2020) and Pousse‐Beltran et al (2020) look a bit oversmoothing without evident asperities as in our model due to the lack of incorporating waveforms for inversion. Our model differs from Melgar et al (2020) mainly in the moment release rate and Asperity D. There does not exist sharp down and up in moment release rate after ~10 s in Melgar et al (2020), and interestingly, their maximum moment release rate is lower than our model in spite of a larger peak slip.…”

“…Despite that teleseismic‐only inversion from USGS shows a very similar bimodal moment rate function as our model, the location of USGS model apparently contradicts the InSAR observations, which is caused by the improper epicenter selection. Pousse‐Beltran et al (2020) use two colinear fault planes with a step over to characterize the rupture; we find that while the two fault planes do increase, the InSAR fits a bit but at the expense of decreasing the waveform fits. In fact, Cheloni and Akinci's (2020) fault geometry inversion using InSAR observations also favors one single fault plane.…”

“…We compare our kinematic model (Figure 2c) with those produced by USGS based on teleseismic waveforms (https://earthquake.usgs.gov/earthquakes/eventpage/us60007ewc/finite-fault), Cheloni and Akinci (2020) and Pousse‐Beltran et al (2020) based on InSAR observations, and Melgar et al (2020) based on joint InSAR and high‐rate GNSS records. Furthermore, we supplement rupture models from each individual data set (see Figure S7) to check their constrains on slip features.…”

Distribution of Interseismic Coupling Along the North and East Anatolian Faults Inferred From InSAR and GPS Data

“…We obtain a pdf of the seismic moment accumulated since 1905 (Figure 4a). The pdf mean is 7.3 × 10 18 N m, its standard deviation 0.8 × 10 18 N m. According to the USGS solution, the seismic moment released during the Elazığ earthquake is 13.87 × 10 18 N m—other solutions find even larger seismic moments (e.g., GCMT, Pousse‐Beltran et al, 2020)—which is much larger than the 7.3 ± 0.8 × 10 18 N m of moment deficit that we estimated since 1905. This seems to indicate that the recent Elazığ earthquake did not rupture the same fault portion than the 1905 earthquake.…”