The 2020 Samos (Aegean Sea) M7 earthquake: a normal fault with rupture
directivity and near surface slip explaining the tsunami generation and
coastal uplift
Abstract
The 30 October 2020 M7 Samos earthquake occurred offshore the
Greece-Turkey cross border region, and will be recalled as among the
deadliest (118 fatalities) that affected both countries. It generated a
strong tsunami and caused coseismic uplift of 20 to 35 cm of the NW part
of the Samos Island. It ruptured a ~60 km long,
north-dipping normal fault, related to the back-arc extension of the
Aegean Sea area. Using picks from regional strong motion and broad-band
waveforms we relocated the mainshock and the aftershocks, applying
suitable velocity models. The closest strong-motion recordings,
constrained the finite fault slip model, suggesting up-dip and westward
propagation of the rupture. The westward rupture propagation is
independently confirmed by the apparent source time functions inferred
using the empirical Green’s function method from near-regional
broad-band and strong-motion waveforms. Static displacements measured by
GNSS stations constrain near surface slip of ~1 m,
explaining the tsunami and the island uplift. The 2020 Samos event
showed that normal faults bounding the basins in the back-arc Aegean
region can host M7 earthquakes and when combined with tsunami
generation, constitute a constant threat for the nearby coastal areas of
both Greece and Turkey.