5:15 PM - 6:45 PM
[SSS08-P06] Aftershock distribution of the 2023 M7.8 Kahramanmaras and M7.5 Ekinozu earthquakes, southeastern Türkiye
Keywords:The 2023 M7.8 Kahramanmaras and M7.5 Ekinozu earthquakes, East Anatolian Fault
On February 6, 2023, two of M > 7 earthquakes occurred in southeastern Türkiye. Their aftershock locations were reported by AFAD (Disaster and Emergency Management Presidency) and Kandilli Observatory and Earthquake Research Institute, Bogazici University (KOERI), respectively, and most of them locate along mainly the East Anatolian fault zone and the Çardak-Sürgü fault zone. However, it is difficult to estimate the fault geometry by using their catalog due to the insufficient accuracy of focal depth.
In this study, we tried to relocate the main- and aftershocks by combining the arrival data of AFAD and KOERI, and the initial hypocenter locations were referred from AFAD catalog.
We adopt the double-difference seismic tomography (tomoFDD, Zhang and Thurber, 2006) to estimate structural heterogeneities and hypocenter locations simultaneously. We use 1-D velocity model of Guvercin et al. (2022) as an initial model. Prior to tomographic inversion, we calculated the average of observed and synthetic arrival time for both P and S phase at each station and use it as the station correction value. In addition, we use the relative arrival times of event pairs whose separation was less than 10 km.
The obtained hypocenter distribution shows different depth range from that of AFAD catalog. The most of aftershocks locate in the range of 3 to 12 km in depth, whereas the AFAD catalog could not constrain the depth well and many of them were fixed at 7 km depth. In many places, the aftershock distribution is aligned in a near-vertical straight line, indicating the location of the subsurface fault plane. Some of them seems to be connected to the surface trace of the active fault, whereas a part of them does not coincide with the surface trace of the active fault. This feature indicates the existence of several buried faults.
For the velocity structure model, the East Anatolian fault was imaged as low velocity zone whereas the Çardak-Sürgü Fault zone was imaged as the boundary between northern high and southern low velocity zone. However, it is difficult to discuss the details since the resolved area was spatially limited.
Acknowledgment: We use the phase picking data from AFAD and KOERI. This research was supported by JSPS Grant-in-Aid for Scientific Research 22K21372.
In this study, we tried to relocate the main- and aftershocks by combining the arrival data of AFAD and KOERI, and the initial hypocenter locations were referred from AFAD catalog.
We adopt the double-difference seismic tomography (tomoFDD, Zhang and Thurber, 2006) to estimate structural heterogeneities and hypocenter locations simultaneously. We use 1-D velocity model of Guvercin et al. (2022) as an initial model. Prior to tomographic inversion, we calculated the average of observed and synthetic arrival time for both P and S phase at each station and use it as the station correction value. In addition, we use the relative arrival times of event pairs whose separation was less than 10 km.
The obtained hypocenter distribution shows different depth range from that of AFAD catalog. The most of aftershocks locate in the range of 3 to 12 km in depth, whereas the AFAD catalog could not constrain the depth well and many of them were fixed at 7 km depth. In many places, the aftershock distribution is aligned in a near-vertical straight line, indicating the location of the subsurface fault plane. Some of them seems to be connected to the surface trace of the active fault, whereas a part of them does not coincide with the surface trace of the active fault. This feature indicates the existence of several buried faults.
For the velocity structure model, the East Anatolian fault was imaged as low velocity zone whereas the Çardak-Sürgü Fault zone was imaged as the boundary between northern high and southern low velocity zone. However, it is difficult to discuss the details since the resolved area was spatially limited.
Acknowledgment: We use the phase picking data from AFAD and KOERI. This research was supported by JSPS Grant-in-Aid for Scientific Research 22K21372.