Akademik Veri Yönetim Sistemi
Seismotectonics of the East Mediterranean-Red Sea region, Hamimi Z.,Nemeth K.,Fowler A-R,Arai S.,Pelaez J.A.,Toni M.,Sawires R., Editör, Springer Nature, London, ss.327-348, 2025
The East Anatolian Fault Zone (EAFZ) and North Anatolian Fault Zone (NAFZ) are ~ 700 km and ~ 1500 km long sinistral and dextral transform fault, respectively, located between Arabian and Eurasian plates, and Anatolian Block. Presently, seismotectonic frame displays complex and heterogeneous seismicity patterns with several significant seismic gaps, swarms and dispersive zones due to rapid change in velocities along the boundary. Understanding of seismotectonics and crustal structure of both fault zones are still crucially important to pose reliable seismic hazard frame for the future studies, although there have been devastating earthquakes in both fault zones in the last 25 years (e.g. 24.01.2020 Mw = 6.8 Sivrice-Elazig earthquake, 06.02.2023 Mw = 7.8 and 7.6 Turkiye/Syria earthquake doublet in EAFZ, and 17.08.1999 Mw = 7.6 Kocaeli, 12.11.1999 Mw = 7.2 Duzce, 14.05.2014 Mw = 6.9 Gokceada-North Aegea earthquake in NAFZ). Therefore, this study first aims to compile significant studies performed near or along these zones utilising dense literature review, and then investigates seismicity, seismotectonics, crustal structural feature and present seismic hazard using stress tensor and local earthquake tomography (LET) analyses for the eastern extremity segments of both zones where they meet in Karliova Triple Junction (KTJ) to understand present state of seismic hazard. Seismicity catalogue includes 100.635 earthquakes in a ± 80 km width zone centred on EAFZ main trend and displays clear clusters on several segments. Depth cross-section of same projected events reveals a concentration in the first 15 km of earth crust and an undulated Conrad discontinuity is observed around this layers for the EAFZ. The 30-year seismicity catalogue that comprises 76.901 limited earthquakes for the projected area of NAFZ identifies several clusters including new potential fault zones which are not mapped and reported. For LET study, we have used 20.130 earthquakes. They have been recorded in the last 15 years (Jan 2010–May 2024), and cover 210.884 P-wave and 148.387 S-wave phase readings. We have also gathered nearly 100 focal mechanisms for seismotectonic, stress tensor and seismic hazard analysis. Data are taken from open source portal of the Disaster and Emergency Management Authority (AFAD) of the Ministry of Interior of Turkish Republic. Fault plane solutions are compiled from AFAD and other resources. Focal mechanisms show stress orientations in consistence with kinematics of fault zones. The inversion of earthquakes focal mechanisms occurred along both the eastern and northern parts of the NAFZ demonstrates that the present-day state of stress is predominantly strike-slip with a consistent approximately N–S trending σHmax (σ1) axis and an E–W trending σHmin (σ3) axis. The inversion yields a N338° E (σ1) and N247° E (σ3) axes inducing a dextral motion along the eastern part of NAFZ. The calculated R value of 0.228, indicating a transtensional character for this stress regime. The inversions give stress states that are characterized by along the northern segments of the EAFZ give N338° E (σ1) and N247° E (σ3) for EAF1 and N338° E (σ1) and N247° E (σ3) for EAF2 inducing sinistral motion and the R values of 0.271 and 0.406 indicate transtensional stress states for both sections. The distributions of the resulting Vp, Vp/Vs values from LET analysis identify low velocity zone (LVZ) and high velocity zone (HVZ) areas down to 30 km depth layers by demonstrating significant anomalies associated with the major tectonic features of the region. A significant low Vp, low Vp/Vs values may present a high seismic hazard for the Yedisu Fault-YF (near KTJ) area as previously reported similar anomaly combination before a Mw = 6.8 earthquake occurred on the EAFZ. On the other hand, 2023 rupture has reached up to Hatay terminated the seismic gap on the EAFZ. But, the DSF preserves its seismic gap feature. For the NAFZ, there is a dangerous seismic gap in Marmara Sea by presenting a major seismic risk not only for Istanbul but also for the whole settlements. This gap is candidate to produce a single rupture up to Mw = 7.7 magnitude by posing additionally a tsunami threat. The seismic gap on the EAFZ was completed with the February 2023 earthquakes.