Complex Dynamic Rupture of an Mw5.8 Intermediate-Depth Earthquake in the Hellenic Slab

Abstract

Earthquakes in the Hellenic slab, traced by tomography down to 1,200 km, occur at depths <200 km with enigmatic origin and dynamics. We study a 2014 Mw5.8 left-lateral strike-slip earthquake originating at a depth of ∼90 km under arc-parallel compression, featuring a small implosive component of the moment tensor. We use well-recorded aftershock as an empirical Green's function to infer reliable apparent source time functions up to 2 Hz. They exhibit multiple peaks with pronounced directivity and serve as input data to infer kinematic and dynamic rupture evolution in Bayesian source inversion. Our finite-fault kinematic and dynamic source models consistently reveal episodic behavior with two prominent asperities, short rupture duration, unilateral propagation, and locally high rupture speed and stress drop. We speculate the event was triggered and driven by dehydration and stress transfer associated with shear deformation and rock compaction.