Time–Space Evolution of Seismic Strain Release in the Area Shocked by the August 24–October 30 Central Italy Seismic Sequence

Abstract

In this study, we analyze the space–time evolution of the seismic strain release in the area shocked by the still ongoing Italian Central Apennines seismic crisis started on August 24, 2016 and culminated with the October 30 main shock of Mw 6.5. Specifically, we examine the variation in time and space of the seismic strain release rate with the aim of identifying the presence of peculiar seismicity patterns, such as seismic gaps, according to the seismic cycle theory. To this end, seismic strain rates are checked for consistency with strain rates from GPS measurements to possibly adjust them for missing events due to limited seismic catalog extension or incompleteness at large magnitudes. Our results has revealed that the seismic crisis followed a long-term quiescence of about 310 years, characterized by the absence of M6.5+ earthquakes, and marked by an almost steady release of seismic deformation. Such temporal gap started after the occurrence of two nearby strong events in 1703 (Valnerina and L’Aquila earthquakes with magnitudes of 6.9 and 6.7, respectively) and terminated with the beginning of the current Central Apennines seismic crisis.