Seismotectonic implications of the 2020 Samos, Greece, M-w 7.0 mainshock based on high-resolution aftershock relocation and source slip model

Abstract

The 30 October 2020, M-w 7.0 Samos mainshock took place in the offshore north of Samos Island in eastern Aegean area, previously struck in 1904 with a comparable magnitude earthquake offshore the southern coastline. The investigation of the aftershock seismicity evolution and the properties of the activated fault network was accomplished with aftershock relocation performed with the double-difference and cross-correlation techniques. The highly accurate relocated seismicity illustrates a well-defined E-W activated structure located deeper than 5 km with an average depth of similar to 12 km. Moment tensor solutions indicate mostly normal faulting with an average T-axis similar to 185(omicron). Strong-motion waveform modeling revealed a N-dipping fault plane with a coseismic slip patch of 36 km x 22 km and a maximum slip equal to 1 m at 12 km depth. The slip is mainly concentrated in a single asperity implying a rupture mode of asperities breaking in isolated earthquakes rather than to cooperate to produce a larger rupture. Coulomb stress calculations unveil increased positive static stress changes values at the locations of the majority of the aftershocks and activation of minor fault segments by stress transfer.