iPlex Lunch Winter-2018

The Central Italy 2016-2017 earthquake sequence has generated three mainshocks: M6.1 24 August, M5.9 26 October, and M6.5 30 October 2016. These events, along with a relevant number of aftershocks, were well recorded by Italian networks. This earthquake sequence occurred in a gap between two earlier damaging events, the 1997 M6.1 Umbria-Marche earthquake to the north-west and the 2009 M6.1 L’Aquila earthquake to the south-east. Analysis of data from this earthquake sequence will likely have worldwide relevance. For example, many recent ground motion models are based on global databases in which the large majority of recordings for normal fault events with M>5.5 are from Italy. This presentation focuses on source attributes and ground motion characteristics of this earthquake sequence. Significant evidences, including surface rupture patterns and inverted finite fault models, point to the earthquakes having been generated on the Mt. Vettore-Mt. Bove fault system (all three mainshocks) and on the northern segment of the Laga Mountains fault system (portion of 24 August event). This information could be used to improve earthquake rupture forecast models taking into account multi-fault ruptures. Ground motion characteristics of mainshocks and selected aftershocks are also presented. Stations at close distance, including near the hanging wall, exhibit fling step in some cases but, remarkably, no obvious rupture directivity. Overall, the data exhibit fast anelastic attenuation at large distances (> 100 km). This feature seems to be persistent throughout all of the recent Italian earthquakes and it is consistent with recent Italy adjusted global ground motion models, but not with a recent Italy-specific model. Outcomes from this study could provide useful information on how to improve future probabilistic seismic hazard analyses in Italy and elsewhere.