Source Parameters of the 2004 Kobarid (Western Slovenia) Seismic Sequence.

Abstract

The Kobarid area (western Slovenia) was struck by two seismic sequences in 1998 and 2004. Corresponding mainshocks, occurred on April 12, 1998 and July 12, 2004, had magnitude MW =5.7 and MW =5.2, respectively and were located 2.6 km away from each other. Both of them were recorded by the Friuli-Venezia Giulia Seismometric Network, managed by the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS), installed in north-eastern Italy (http://www.crs.inogs.it). During the sequences, the network recorded hundreds of aftershocks and both standard locations and duration magnitude (MD) estimations were performed. The seismic activity lasted 198 and 135 days, respectively and consisted of 700 events with MD in the range [1.5, 4.6] and 300 events with MD in the range [1.1, 3.6], respectively (Bressan et al., 2009). In this work, we estimate the seismic moment, M0, the corner frequency, fC, the Brune stress drop, ΔσB, the apparent stress, σa and the radiated energy, ES, of the mainshock and of 164 aftershocks of the Kobarid (2004) seismic sequence. The obtained results are compared with two previous analysis performed in the same region, concerning the source parameter scaling of the background seismicity (Franceschina et al., 2006) and of other seismic sequences (Bressan et al., 2007) occurred in the area.