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

Abstract

The North Anatolian Fault (NAF) has produced numerous major earthquakes. After decades of quiescence, the Mw 6.8 Elazığ earthquake (24 January 2020) has recently reminded us that the East Anatolian Fault (EAF) is also capable of producing significant earthquakes. To better estimate the seismic hazard associated with these two faults, we jointly invert interferometric synthetic aperture radar (InSAR) and GPS data to image the spatial distribution of interseismic coupling along the eastern part of both the NAF and EAF. We perform the inversion in a Bayesian framework, enabling to estimate uncertainties on both long‐term relative plate motion and coupling. We find that coupling is high and deep (0–20 km) on the NAF and heterogeneous and superficial (0–5 km) on the EAF. Our model predicts that the Elazığ earthquake released between 200 and 250 years of accumulated moment, suggesting a bicentennial recurrence time.

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

“…However, all of the InSAR tracks used by Cavalié and Jónsson (2014) and Walters et al (2014) do not show any sharp displacement discontinuities, indicating that the fault creep should not have reached the surface during the InSAR observation period and is thus possibly a transitory phenomenon. Taking all the above into account, we believe that besides imparted by past events (Nalbant et al, 2002), heterogeneous stress distribution is being built up constantly during the interseismic period on locked patches along EAFZ as revealed by a recent study by Bletery et al (2020), which can then fail separately or collectively during earthquakes (Kaneko et al, 2010), and this is probably the main reason for the irregularity of earthquake intervals along EAFZ.…”

“…A number of previous studies have also tried to estimate the fault locking depth and slip rate using InSAR and GNSS velocity fields (e.g., Bletery et al, 2020;Cavalié & Jónsson, 2014;Walters et al, 2014), which contribute to evaluate the strain building and identify the slip deficits. With regard to the geodetic approach, a long outstanding problem is that there exists a trade-off in the estimation of slip rates and locking depth (Savage & Burford, 1973).…”

A Stochastic View of the 2020 ElazığMw6.8 Earthquake (Turkey)

“…10.1029/2020GL090704 9 of 13 et al, 2020), shallow interseismic slip deficit (Bletery et al, 2020) and our assumed fault trace for the 2020 Elazığ event (thick black line). (b) Possible rupture extents for the four most recent M w > 6.5 earthquakes that struck the mapped segments of the EAF before the Elazığ event, inferred from Ambraseys (1989) and Hubert-Ferrari et al (2020).…”

“…We make the same comparison for the East Palu segment, and show that the moment released by the 2010 M w 6.1 Kovancılar earthquake well matches the moment accumulated from the 1971 Bingöl event to 2010 (1.58 ± 0.2 ≈ 2.19 ± 0.56 10 18 N m, Figure 4d), suggesting this portion of the EAF actually ruptured during the 1971 event, and that all of the accumulated moment has been released Comparison between the spatial distributions of the 2020 Elazığ earthquake rupture, historical earthquakes, highly coupled sections of the EAF, and seismic moment accumulated since last historical rupture in relation with seismic moment released by the most recent event. (a) Map view of two segments the East Anatolian Fault (black lines), overlayed with historical and recent seismicity from 1900 to January 2020 (Retrieved from AFAD, 2020; NEIC, 2020; Melgar et al, 2020), shallow interseismic slip deficit (Bletery et al, 2020) and our assumed fault trace for the 2020 Elazığ event (thick black line). (b) Possible rupture extents for the four most recent M w > 6.5 earthquakes that struck the mapped segments of the EAF before the Elazığ event, inferred from Ambraseys (1989) and Hubert-Ferrari et al (2020).…”

“…4D). To do so, we calculate the seismic moment for the area ruptured by the event according to our slip model, and account for uncertainties in ruptured area (σ = 3 km 2 ), shear modulus (µ = 2.8 ± 0.3 10 1 GPa), coupling and slip rates (according to Bletery et al, 2020 Although the portions of the EAF that have been affected by the Elazıg and Kovancılar events show seismic activity in the 20 years preceding these events, the West Palu segment is characterized by relatively low seismic activity (Fig. 4).…”