Seismically induced ground effects of the December 2013 - January 2014 Matese seismic sequence (southern Apennines, Italy)

The Matese area has recorded in historical times a number of earthquakes with magnitude around 7 and frequent moderate earthquakes (Rovida et al., 2011). Active tectonics in this area is testified by geological, geomorphological and morphometrical data (Valente et al., 2015a). From December 2013 to January 2014, the SE sector of the Matese massif has been affected by a low to moderate magnitude seismic sequence. The main event, with Mw 5.0 according to ISIDE (http://iside.rm.ingv.it) occurred on December 29th 2013 with hypocentral depth ranging from 12 km to 20 km, and was characterized by a NW-SE trending extensional focal mechanism (Ferranti et al., 2015) The 2013-2014 seismic sequence caused ground effects in an area of about 90 km2 (Valente et al., 2015b). Several rock falls affected the carbonate ridges in the area around the villages of San Gregorio Matese and Pietraroja. Discharge variations and an increase of turbidity in one of the major springs have been recorded. Local people also described the occurrence of a flame just a few seconds before the main shock. A coseismic rupture in the carbonate bedrock on the SW border of a small intramontane basin located about 1.5 km SE of the Mt. Airola was reported by local people. The rupture is striking N120, NE facing, ~0.3 m high and 50 m long. The rupture affects a rectilinear scarp bounding the basin to the SW and is dissected by a hanging valley. These features suggest the occurrence of a fault bounding the Mt. Airola basin to the SW. We have carried out a geoelectrical investigation in order to reconstruct the geometry of the Mt. Airola basin, and to derive information on the features of the coseismic rupture. The results constrain the geometry of the carbonate substratum of the Mt. Airola basin and point to the occurrence of an abrupt, subvertical contact between the carbonates and the Quaternary filling of the basin. T