Coseismic and Postseismic Imaging of a Composite Fault System: The Samos 2020 Mw 7.0 Sequence

The 2020 Mw 7.0 Samos earthquake (eastern Aegean Sea) provides a rare chance to study the ongoing interaction of normal and strike-slip faulting during an aftershock sequence in a suspected transfer zone with differential deformation style. After assessing them for possible site-effect influence, we first backproject local strong-motion data to elicit the high-frequency (HF) radiation for the main seismic event using the Source Scanning Algorithm. Our results indicate the existence of multiple HF radiators during the main rupture. Second, we construct a new, high-precision catalog for the aftershock sequence utilizing a deep-learning-based detector and picker. This new catalog contains thousands of additional seismic events compared with the routine catalogs built by local agencies and is accompanied by an enhanced dataset of fault-plane solutions determined with automated techniques. Complex fault networks activated during the aftershock period are mapped in detail, indicating the existence of an active transtensional, possibly asymmetric, basin offshore Samos Island. This detailed seismological characterization of Samos sequence leads to an improved understanding of the controlling mechanisms that operate concurrently during a sequence in a transtensional type of system.