GNGTS 2018 - 37° Convegno Nazionale

GNGTS 2018 S essione 1.2 233 Somma-Vesuvius) and Sarno plain (Irollo et al. , 2005). Both plains are bounded by NE-SW trending normal fault systems (Irollo et al. , 2005), which have been included in the national database of active and capable faults (www.sgi2.isprambiente.it/ithacaweb/viewer/ ). Historical seismicity points to the occurrence of few low to moderate magnitude earthquakes since 1000 A.D. The strongest events are the 5 th December 1499 earthquake (Mw = 5.56) and the 31 st March 1737 earthquake (Mw = 5.10), located NW and N of the Sarno Mts., respectively. The most recent, and strongest, seismic event occurred the 27 th April 1930 (Mw = 4.9) about 6 km SE of the Sarno town (Rovida et al. , 2016). We are carrying out a detailed scale geological and geomorphological analysis of the NE border of the Sarno plain aimed at identifying evidence of recent faulting in the study area. Our study is based on analysis of 1:5000 topographic maps (Technical Map of the Campania Region) and high resolution (1X1 m) dtm, on field surveys and collection of subsurface stratigraphical data (drillings and borehole logs, collectively and ranging in depth from 20 to 250 m). Geological and geomorphological setting. The study area includes the mountain front, mainly NW-SE trending, of the carbonate Sarno Mts. and adjoining sector of the plain, which extends from the town of Sarno, to the NW, to the Lavorate settlement to the SE (Fig. 1). In the area spanning from Sarno to Lavorate, a localized depocenter (hereinafter named Lavorate basin) occurs in a deep indentation of the mountain front (Fig. 1). The Lavorate basin is bounded to the NW by a rectilinear escarpment and is filled by alluvial fan deposits interbedded with tephra layers. Slope breccia and colluvial deposits occur locally at the toe of the carbonate slopes. The alluvial fan system consists of two generation of entrenched fans, with the oldest fans being steeper than the youngest ones. A sinkhole (Fossa San Vito area) affects the alluvial fans (Fig. 1). The alluvial fans pass laterally into the alluvial fill of the Sarno plain, which are composed by alluvial sediments interbedded with volcanic deposits, paleosoils and peat Fig. 1 - Geological map of the study area. 1) Allucial deposits (Holocene); 2) 2 nd generation alluvial fan (Upper Pleistocene - Holocene); 3) 1 st generation alluvial fan (Middle to Upper Pleistocene); 4) debris slope deposits (Middle to Upper Pleistocene); 5) Carbonate bedrock (Mesozoic); 6) Fossa San Vito sinkhole; 7) quarry; 8) water flow tank; 9) hydrographic apex; 10) borehole; 11) normal fault (certain); 12) normal fault (inferred); 13) trace of geological cross section; 14) 5m contour line; 15) 25 m contour line.