Insights from the 06 February 2023 Mw 7.8 Kahramanmaras earthquake: evidence into an active strike-slip faulting along the East Anatolian Fault Zone

Abstract

On February 6, 2023, a magnitude 7.8 earthquake and subsequent strong seismic activity struck in Kahramanmaras region, causing over 50,000 deaths in Turkey and Syria. The earthquake resulted in a surface rupture of the East Anatolian Fault Zone (EAFZ) spanning approximately 300 km. To gain new insights into the neotectonic and current stress field in the region, we compiled 141 focal mechanism solutions (FMS) of earthquakes (with magnitude M ≥ 3) that occurred along the EAFZ between 05/01/2003 and 27/02/2023. Stress inversion, by using the Win-Tensor program, indicated a predominant strike-slip tectonic regime, with few normal and thrust events related to complex fault geometry along the principal displacement zone. The calculated pressure/tension axes in the first order stress field are mainly sub-horizontal, with a maximum horizontal compressive stress (SHmax) direction of N19 ± 9.9° E, which aligns well with the slip character of the EAFZ. To reconstruct the second and third order stress fields, the study area was subdivided into five zones based on their structures and geomorphological characteristics. Reduced stress tensors were obtained for each zone, indicating a small rotation of SHmax directions under a prevailing strike-slip faulting regime. The maximum (σ1) and minimum (σ3) stress axes are nearly horizontal; while the intermediate (σ2) stress axis is nearly vertical, consistent with a predominant strike-slip regime. The results show, also, that the Kahramanmaras earthquake was caused by the neotectonic reactivation of northeast-striking sinistral strike-slip fault, with a north–south-oriented maximum horizontal stress axis. The neotectonic activity along the EAFZ aligns well with the collision models between the Arabian and Eurasian plates. Finally, a detailed seismic hazard assessment is required for the EAFZ and nearby regions.