6th International Conference on Earthquake Engineering and Seismology, Kocaeli, Turkey, 13 - 15 October 2021, pp.1-10
The East Anatolian Fault zone is one of the active fault zone causing several destructive earthquakes in the instrumental and historical periods. This seismic activity is generally associated with the moving of the Arabian, Eurasian, and African plates. The region has recently experienced a strong earthquake which is the Elazığ earthquake (Mw=6.8) that occurred on January 24, 2020, according to the Disaster and Emergency Management Presidency (AFAD). Developed regional shear-wave velocity distribution is very important for a better seismic characterization (seismic locations, source parameters, and focal depths), regional seismicity, and seismic hazard assessment. The main goals of this study are to identify the crust and upper mantle S-wave velocity structure along the EAFZ and to compare the results of two different joint inversion algorithms. As the first method, the joint inversion procedure developed by Julia et al. (2000) is used. This method involves jointly inverting the P-Receiver Functions and Rayleigh wave phase velocities. As the second method, it is applied simultaneous inversion of the P-Receiver Functions and S-Receiver Functions (PRFs and SRFs), similar to the simulated annealing method. In this technique, PRFs are obtained from Vinnik (1977), while SRFs are computed from Farra and Vinnik (2000). For the data sets, the broadband stations of the AFAD (FRT, MAYA, AZEY, AKCA, NAR, RHAN) and Kandilli Observatory and Earthquake Research Institute (KARO, BNGB, SVRC) are used to obtain regional (Δ ≤ 10°) and teleseismic (30° ≤ Δ ≤ 90°) events. According to the results, the first algorithm reveals more effective results in the upper-crust, while the second algorithm includes more effective results in the uppermost mantle. The crustal low-velocity zones beneath the stations are observed at a depth of ~12 km. The depth distribution of earthquake hypocenters generally occurs between 10 and 20 km in the time interval 2000-2020. This shallow seismicity is compatible with S-wave velocity variations and strike-slip motion. The crust-mantle transition along the EAFZ varies from 32 km to 44 km. Finally, this study gives that the lithospheric S-wave velocity structure corresponds with the regional tectonics of the studied region.