Asperity-like (segmented) structure of the 6 February 2023 Turkish earthquakes

Abstract

Key to studies of the rupture process is the identification of its major segmentation into asperities. Common multi-parametric methods invert for a continuous slip distribution; they usually rely on a predefined fault position, nucleation point, planarity, smoothing, etc. Here we propose more flexible low-parametric inversions - multi-point seismic source models, and multi-patch GPS models. We study the recent Mw 7.8 and 7.5 earthquakes in the Eastern-Anatolian fault system, recorded in a high-quality near-regional network of seismic strong motion and GPS stations. Using 40 seismic stations at epicentral distances ~20-300 km, we seek position, time, and DC-constrained mechanism of point-source subevents by a modified iterative deconvolution. We robustly resolve a small number of major asperities and demonstrate bilateral moment release for both earthquakes. Variations of the focal mechanism along the mapped faults are indicated. The inversion of GPS data for finite-fault patches confirms the asperity-like character of the events and validates along-fault changes of the focal mechanism.