GNGTS 2018 - 37° Convegno Nazionale

GNGTS 2018 S essione 1.1 133 Reasenberg E.A.; 1985: Second-order moment of central California seismicity . J. Geophys. Res., 90 , 5479-5495. Reasenberg P. e Oppenheimer D.; 1985: FPFIT, FPPLOT and FPPAGE: FORTRAN computer programs for calculating and displaying earthquake fault plane solutions . USGS Open-file Report, 85-730, 109. Rovida A., Locati M., Camassi R., Lolli B. e Gasperini P. (eds); 2016: CPTI15, the 2015 version of the Parametric Catalogue of Italian Earthquakes . Istituto Nazionale di Geofisica e Vulcanologia. doi :http://doi.org/10.6092/ INGV.IT -CPTI15 Santini S., Saggese F., Megna A. e Mazzoli S.; 2011: A note on central-northern Marche seismicity: new focal mechanisms for events recorded in years 2003-2009 . Bollettino di Geofisica Teorica ed Applicata, 52 , 639-649, doi 10.4430/bgta0025. Wiemer S.; 2001: A software package to analyze seismicity. ZMAP . Seism. Res. Lett., 72 , 373-382. THE INSTRUMENTAL SEISMICITY OF THE SOUTHWEST MATESE MASSIF (SANNIO-MATESE AREA, SOUTHERN APENNINES - ITALY): FIRST RESULTS G. Milano Osservatorio Vesuviano - INGV Sezione di Napoli, Italy Introduction. The Matese Massif is the major mountain range of the Campania-Molise segment of the Southern Apennines. It is a part of the Sannio-Matese area, which stretches from southern Abruzzo to northeastern Campania, and includes the cities of Isernia, Campobasso and Benevento. This area is considered one of the most active seismic regions of the Italian peninsula and the Massif is located among the seismogenic sources of large destructive (I o >X MCS) historical earthquakes (e.g. 1349 M W =6.5; 1456 M W =7.0; 1688, M W = 6.6; 1805, M W = 6.8; DISS 3.2.1., 2018; Fig. 1). In the last 20 years the seismic activity along and close to the Matese Massif (Fig. 1) has been prevalently characterized by the occurrence of sparse few single events of low energy (M L <2.5) with hypocenters prevalently within the uppermost crust. In addition, low magnitude seismic sequences (M<4.5) occurred in the south-eastern (1997-98, M Lmax =4.2) in the north-western (2001, M Lmax =3.6) edges of the Massif (Milano et al. , 2008), respectively and, recently (2016, M Wmax 4.3), in proximity of the northeast edge (Milano 2016; Moretti et al. , 2017). Last relevant seismic sequence occurred between the late 2013-early 2014 following an M W =5.0 earthquake. This sequence struck the internal part of the Massif in an area where no evidence of active faulting has been recorded so far. Seismological investigation on this sequence (Milano, 2014) integrated by geological and geodetic data suggest that the sequence has developed along a SW dipping NNW-SSE striking normal fault, ~10 km long, confined in the 10-20 km depth range (Ferranti et al. , 2015). The SW-dipping plane as the rupture plane along which this sequence has developed has been also suggested by Convertito et al. (2016). The earthquakes of 1349, 1688 and 1805 had epicenter falling close to the Matese Massif. While the earthquake of 1805 affected the northern slope of the Massif, the other two affected the southern side. The 1688 earthquake, with Intensity equal to the XI degree MCS, had epicenter in proximity of Cerreto Sannita, located on the southeast side of the Massif, that was completely destroyed. On the contrary to the fairly well documented 1688 and 1805 earthquakes, the 1349 earthquake, given its age, stands out due to the lack of reliable and sufficiently vast historical documentation. This seismic crisis includes at least three main shocks all, probably, occurring on 9 September. The southern-most shock of the sequence affected a large NW-SE area amongst the Lazio-Molise-Campania borders with epicenter within the Venafro plain, this last located to