GNGTS 2014 - Atti del 33° Convegno Nazionale

GNGTS 2014 S essione 1.1 39 by ISPRA in 2013 across this fault, with the aim of characterizing its capability in terms of seismic and surface faulting potential. Paleoseismological analysis. In order to better locate the most suitable trenching site, a geophysical survey was performed before, consisting of ERT (Electrical Resistivity Tomogra- phy) profiles and a seismic refraction tomography line. According to the results of these pre- liminary analyses, the site selected for trenching is located north-west of the historical centre of the village (Fig. 1), where morphotectonic observations and geophysical data were consistently indicating the occurrence of a fault cutting up to the surface. Both trench walls were logged in detail, and bulk samples, taken from both walls, were dated through the radiocarbon method, namely accelerator mass spectrometry (AMS), at the Center for Dating and Diagnostics (CEDAD) of the University of Salento. The detailed analy- sis of the stratigraphy exposed in the trench walls (Fig. 3) and the obtained ages (Tab. 1) have confirmed that the fault ruptured repeatedly during the Holocene. Fig. 2 – A) Panoramic view of the fault scarp related to the Demetrio fault. The orange stripe (fencing net) evidences the trench site. B) Geological profile across the fault (location in Fig. 1). Legend: 1) fan delta conglomerates (Lower to Middle Pleistocene); 2) gravels and sands (upper part of Middle Pleistocene). Modified, after Working Group MS–AQ (2010). Tab. 1 - Calibrated radiocarbon ages of samples. All datings (AMS) carried out at the Center for Dating and Diagnostics (CEDAD) of the University of Salento. Sample Radiocarbon Age (BP) δ 13C (‰) Calibrated ages (Range 2 σ ) SD61 4070 ± 45 -25.6 ± 0.5 2760 BC (81.3%) 2470 BC SD62 18944 ± 80 -20.8 ± 0.8 21100 BC (95.4%) 20550 BC SD64 7858 ± 60 -38.3 ± 0.7 7030 BC (95.4%) 6570 BC SD63 6359 ± 60 -29.3 ± 0.6 5470 BC (95.4%) 5220 BC SD65 4717 ± 45 -38.4 ± 0.5 3640 BC (53.8%) 3480 BC SD43 14960 ± 65 -31.3 ± 0.5 16430 BC (95.4%) 16010 BC SD50 38344 ± 400 -31.4 ± 0.7 41100 BC (95.4%) 39900 BC