Hypocenter location accuracy and seismicity distribution in the Central Apennines (Italy)

In this paper, we analyse the seismicity distribution in the Central Apennines (Italy) using the recordings of the Rete Sismometrica Marchigiana (RSM). In particular, the selected events are relocated using a 1-D model calculated by means of an inversion procedure. The robustness of the 1-D model and the location accuracy are tested. The capability of the RSM to well constrain crustal and subcrustal events in the studied area is discussed. We find that in the inner side of the chain the seismicity lies in the upper crustal layers, following the structural trend of the Apenninic belt. A W-deepening of the events is observed in the Apenninic foredeep, where the seismicity is mainly confined in the lower crust. This evidence implies the deepening of the brittle to ductile transition. Some well-located subcrustal events are found. Their locations seem to confirm the W-dipping subduction of the Adriatic lithosphere beneath the Apennines.