This research provides a comprehensive analysis of the tectonic control mechanisms and characteristics of the seismic environment within the East Anatolia Fault Zone (EAFZ) through the creation of a high-precision earthquake catalog. A dual methodology was employed, incorporating absolute positioning via HypoInverse and relative positioning through HypoTD, to accurately relocate 105,690 seismic events that occurred in the study area from January 1, 2010, to July 31, 2024, thereby producing a detailed earthquake catalog for the EAFZ region. The analysis encompassed the spatiotemporal evolution of the b-value derived from the earthquake catalog, stress field inversion based on 1,065 focal mechanism solutions, and the double earthquake sequence of Mw7.8 and Mw7.6 that occurred in Türkiye in 2023.The spatiotemporal characteristics of the seismic events indicate that seismic activity along the southern branch of the East Anatolia Fault (EAF) and the northern branch of the Surgu-Misis Fault (SMF) displays a double-belt distribution, with the majority of focal depths ranging from 5 km to 17.5 km, predominantly consisting of shallow earthquakes. The seismic activity along the EAF exhibits a migration pattern from northeast to southwest, with spatial clustering that is significantly associated with the structural segmentation of the fault. The b-value demonstrated a decline from approximately 0.8 to 0.5 shortly before the Mw6.8 earthquake in 2020, and a further decrease from around 1.0 and 0.7 to approximately 0.3 prior to the Mw7.8 and Mw7.6 earthquakes in 2023, respectively. This trend indicates varying degrees of reduction in b-values preceding major seismic events, suggesting a short-term destabilization precursor related to the critical stress state surrounding the source area. The stress field inversion analysis reveals that the middle segment of the EAF and the western segment of the SMF represent a principal compressive stress concentration zone oriented NNW-SEE, supporting the combined mechanisms of Arabian Plate subduction and Eurasian Plate resistance. The Mw7.8 earthquake in 2023 occurred in a region characterized by low seismic activity and a low b-value (~ 0.55), while the Mw7.6 earthquake was located in an area of low seismic activity but relatively high b-value (~ 0.70), reflecting significant disparities in the stress accumulation states across different fault segments during these two notable seismic events. The co-seismic supershear effect associated with both earthquakes resulted in a continuous decline in the b-value within the triangular area formed by the EAF and SMF, accompanied by an increasing degree of locking, which indicates an ongoing risk of future significant earthquakes.
Liu et al. (Tue,) studied this question.