Seismic Monitoring in Northeastern Italy: A Ten-year Experience

Northeastern Italy (NEI), bordering Slovenia and Austria, consists of the Friuli-Venezia Giulia, Veneto, and Trentino-Alto Adige regions. The area includes the Italian part of the southeastern Alps to the north, and the Veneto and Friuli Plains to the south. Together with its neighboring regions of southern Austria and western Slovenia, this is possibly the most tectonically active area of the Alpine Arc in the present age. The region features the highest seismicity in the Alps, although it can be rated only as moderate level in general terms. According to the CPTI04 catalog (CPTI Working Group, 2004), six earthquakes with MCS intensity greater or equal to IX have struck the area in the last 1,000 years, all with estimated magnitude not exceeding M 6.6 (Figure 1). The last of these occurred in central Friuli on 6 May 1976 ( ML 6.4). Except during the 1976 sequence, magnitude 5.5 or greater earthquakes have occurred only four times in the last century: 1924 and 1928 Tolmezzo, 1936 Cansiglio (Slejko et al. , 1989), and 1998 Bovec, Slovenia, just across the Italian border (Bajc et al. , 2001). Instrumental seismological observations in NEI started at the end of the 19th century with a few observatories in Italy and the former Hapsburg Empire. Since that time, the reference station for the area is in Trieste (Finetti and Morelli, 1972). In 1931 it was taken over by what is now the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS). It later became part of the World Wide Standardized Seismographic Network (WWSSN, station code TRI-117). Since 1996 the station has been equipped with a Streckeisen STS 1 broadband seismometer managed in collaboration with the Dipartimento di Scienze della Terra dell'Universita di Trieste (DST). It is included in the Mediterranean Very Broadband Seismographic Network (MEDNET) as …