GNGTS 2018 - 37° Convegno Nazionale

GNGTS 2018 S essione 1.1 157 Fig. 1 - DEM of the northern Campania region showing main faults (from Vitale and Ciarcia, 2018) and epicentral distribution of the relocated seismicity between 2009 and 2017. Coloured boxes indicates the three ridges (CR-Caserta Ridge, AR-Avella Ridge, SR-Sarno Ridge) analyzed in this work. architecture of the Campania Plain is very articulated. Buried ridges and local depocenters (e. g. Volturno, Acerra and Sarno basins) are allegedly controlled by major E to NE striking normal faults, whose eastern section impinges into the western foothills of the Apennines, where the concealed or exposed structural boundary is represented by major NW-SE to WNW-ESE striking faults. To date, however, virtually no structural information are available regarding the kinematics of these faults. The seismicity of the Campania portion of the Apennines is very articulated. The strongest historical earthquakes that have occurred in the Apennines were related to NW– SE normal faults. The most recent destructive earthquakes occurred in 1930 (M 6.7), 1962 (M 6.2) and 1980 (M 6.9). The focal mechanism of the latter event (Gasparini et al. , 1985) show normal solutions with a NE–SW trending T-axis, in agreement with the strain regime acting in the Southern Apennines (Montone and Mariucci al., 2016). In the last 30 years, seismicity is characterized by isolated event with M<3.5 and by the occurrence of low energy seismic sequences and swarms (M max 4.6) with hypocentres within the first 15 km of the crust (Milano et al., 2008). With the exception of the local seismicity of Vesuvio and Campi Flegrei volcanic areas, characterized by single and/or swarm-type activity of low energy (M<2.5), the background seismicity in the Campanian plain is characterized by temporally and spatially isolated events with magnitudes of less than 3.0. Seismic clusters are located close to the Massico mountain ridge (Gaudiosi et al. , 2012, Luiso et al. , 2018) in the north-western sector of the plain, and along the Avella mountain ridge. Offshore, isolated events occur (Mmax 3.7) at a depth not exceeding 13 km (Milano et al. , 2004). To better understand the structural interaction between these sectors, and how active and seismogenic deformation is expressed in each of them, we started a multidisciplinary study integrating seismological and geological-structural data. We focused on a NE-SW trending regional transect spanning the submerged shelf, the Campania Plain, the western margin and the axis of the northern Campanian Apennines. Analysis in the Campanian Plain portion of the transect is based on merging different approches and datasets including: 1) geometric and kinematic characterization of structures responsible for major tectonic processes at the border between the margin and the chain; 2) characterization of the background seismicity in order to identify active seimogenic volumes. We present the preliminary results of field geological-structural analysis, which have provided a first definition of the geometry and kinematics connected to major faults and that allow to shed light on the tectonic processes which have led to the growth of the Plain. We studied the faults exposed along the western flank of the Apennines, in their southern- central portion. In particular, in this preliminary work, we focused on the Tifatini (Caserta area), Avella and Sarno ridges. We measured slip indicators on both major fault surfaces where exposed and on secondary faults in the immediate footwall of concealed major faults in order to retrieve the kinematics on the latter structures.