Decadal change of the Apulia microplate motion preceding the MW 6.4, 26 November 2019 Durrës (Albania) earthquake

Abstract

It is commonly assumed that the motions of tectonic plates remain steady over the earthquake cycle. This assumption is based on the notion that stresses associated with the cycle may not be sufficient to overcome the asthenosphere viscous resistance at the lithosphere base, which counters plate-motion changes. However, this remains to be verified. Recent inferences on the asthenosphere viscosity/thickness from modelling of glacial rebound data constrain the amount of viscous resistance needed to alter plate motions. In light of these recent findings, it is conceivable that stresses associated with the earthquake cycle are large enough to impact motions of microplates or small-/medium-sized plates. Here we show that the contemporary motion of the Apulia microplate slowed down by ∼20% and turned westward by ∼10∘ during the decade preceding the MW 6.4, 26 November 2019 Durrës (Albania) earthquake, which struck the Apulia eastern margin with the Eurasia plate. We make a statistical comparison between estimates of the torque variation required for Apulia to generate the observed slowdown, and parameterised estimates of the torque variation imparted to Apulia by the interseismic stress buildup during the decade before the 2019 Durrës earthquake. We conclude that the Apulia motion change likely resulted from the interseismic stress buildup associated with the Durrës earthquake cycle.