On the Increase of Background Seismicity Rate during the 1997-1998 Umbria-Marche, Central Italy, Sequence: Apparent Variation or Fluid-Driven Triggering?

摘要

We investigate the temporal evolution of background seismicity rate in the Umbria-Marche sector of the northern Apennines that was struck by the 1997–1998 Colfiorito seismic sequence. Specifically, we apply the Epidemic-Type Aftershock Sequences (ETAS) model to separate the background seismicity rate from the coseismic triggered rate of earthquake production. Analyzed data are extracted from the Catalogo della Sismicità Italiana (CSI1.1, catalog of Italian seismicity) 1981–2002, which contains for the study area 12.163 events with M_L