2023 Earthquake Doublet in Türkiye Reveals the Complexities of the East Anatolian Fault Zone: Insights from Aftershock Patterns and Moment Tensor Solutions

Abstract

On February 6th 2023, Mw7.8 Kahramanmaraş earthquake sequence ruptured a section of ~300 km of the East Anatolian Fault (EAF). The Mw7.8 earthquake was followed by a Mw7.6 event rupturing E-W oriented Çardak Fault on the north of the EAF, ~9 hours later. The ruptured segments characterized by seismic gaps, localized clusters and extensive diffuse zones in the interseismic period. Hence, our understanding of the geometry and kinematics of the western and northern segments remains limited. The February 6, 2023, Mw7.8 Kahramanmaraş on the main branch and Mw7.6 Elbistan earthquakes on the northern branch shed light on the nature of these relatively silent segments. We constructed a comprehensive catalog of ~32,000 earthquakes that occurred between February 6th 2023 and March 30th 2023, using a deep-neural-network-based picker. In addition, 170 earthquake source mechanisms with M3.5+ were obtained from regional moment tensor inversion. The spatial distribution of the aftershocks shows that most of the activity cluster around the fault bends and major depressions. Previously unmapped and inactive secondary faults of varying lengths are identified within these geometrical complexities. Results suggests extension along the Karasu Valley, compression occurring along the Erkenek Segment, reactivation of basin faults near the Narlı Fault Zone and the persistent shallow seismic creep of the Pütürge Segment. The analysis of seismicity and earthquake source mechanisms along the northern branch reveals the structures of previously inactive faults, both near the extensional Göksun Bend in the west and the compressional Nurhak Fault Complex in the east. In this presentation, we present the intricacies of previously quiet segments of the EAFZ and how secondary faults and geometrical discontinuities along the EAF played a role in shaping the 2023 Türkiye Doublet earthquakes.