Temporal stress perturbations generated by the Kahramanmaraş Mw 7.8 & 7.5 2023 seismic doublet in Türkiye

Abstract

Devastating earthquakes (M_w7.8 and M_w7.6) struck Eastern Türkiye in February 2023, resulting in widespread casualties and injuries. The mechanism of both events was strike-slip having different fault plane orientations with aftershock locations following their corresponding strike directions. Tectonically, these events were associated with the Eastern Anatolian Fault system, situated at the intersection of three tectonic plates (Arabian, African, and Anatolian Plates). The b-value (slope of frequency magnitude distribution) of background seismic activity is investigated, showing temporal fluctuations over 9 years time period preceding the main earthquake. A systematic decreasing trend in the b-value, approaching its lowest value (0.71 ± 0.04) within a couple of years before the mainshock, suggests an elevated differential stress in this region. Before the mainshock, poor migration (0.05 km/day) of the events within a cluster at 37.3° – 37.5° latitude was observed. Three distinct characteristic clusters (two around the large events and a third to the south of the first event) were triggered during the aftershock sequence. The aftershock decay slope was greater than unity (p-value = 1.24 ± 0.02 of Omori’s law) and a duration of 9.3 ± 0.9 years was estimated for overall aftershock sequences. The first sequence (M_w7.8) has a time variant p-values (initially small value then increase after 5 days) depicts a heterogeneous post-seismic stress distribution as compared to the second one. These results will improve short-term aftershock forecasting and hazard mitigation.