Relevant site effects related to impedance contrast can be expected in basins filled by a thick sequence of soft sediments above a stiff pre-Quaternary carbonate bedrock such as in the intermontane basins of the Italian Apennines. We investigate the Sulmona basin, a tectonic depression elongated for ~22 km in the NW-SE direction and up to 5-7 km wide, in the Abruzzi’s Central Appennines. The origin of the basin is due to the Quaternary activity of the Mt. Morrone normal fault which dips to the southwest limiting the NE edge of the basin, able to produce Mw 6.5-6.7 earthquakes. The basin infill of such a half-graben shows a typical triangular geometry thickening toward the Mt. Morrone fault plane, where the fluvial-lacustrine sequence should reach up to 500-600 m of thickness (Miccadei et al., 1999). However, the entire sequence has never been observed in either an outcrop or in a borehole. The detected unfavorable local site effects condition that emerged from level 1 of Seismic Microzonation determines a high seismic hazard level for the city of Sulmona and neighboring villages. The present work focuses on the geotechnical characterization of lacustrine soils cored and sampled hundreds of meters deep. The shear wave velocity rofile and the cyclic nonlinear properties in the lacustrine sediments have been determined. A stiffness-depth relation from cyclic laboratory tests is derived and calibrated with available in-hole tests. Results have been integrated with VS profiles from 2D seismic arrays that constrained the whole thickness of fluvio-lacustrine sediments. A validation of the Vs profile has been finally realized by comparing computed resonance frequencies with xperimental values derived from HVSR analyses on microtremor measurements. We present a geological cross-section, selected to investigate the seismic response through 2D numerical analysis in the 3rd level of the seismic microzonation study, as a representative eotechnical model of the Sulmona city center.
First results from level 3 Seismic Microzonation of Sulmona (AQ), Central Italy
Ciaglia S.;Francescone M.;Pagliaroli A.;Amoroso S.;Salvatore N.;Giallini S.;Milana G.;Vassallo M.;Basi M.;Pizzi A.
2024-01-01
Abstract
Relevant site effects related to impedance contrast can be expected in basins filled by a thick sequence of soft sediments above a stiff pre-Quaternary carbonate bedrock such as in the intermontane basins of the Italian Apennines. We investigate the Sulmona basin, a tectonic depression elongated for ~22 km in the NW-SE direction and up to 5-7 km wide, in the Abruzzi’s Central Appennines. The origin of the basin is due to the Quaternary activity of the Mt. Morrone normal fault which dips to the southwest limiting the NE edge of the basin, able to produce Mw 6.5-6.7 earthquakes. The basin infill of such a half-graben shows a typical triangular geometry thickening toward the Mt. Morrone fault plane, where the fluvial-lacustrine sequence should reach up to 500-600 m of thickness (Miccadei et al., 1999). However, the entire sequence has never been observed in either an outcrop or in a borehole. The detected unfavorable local site effects condition that emerged from level 1 of Seismic Microzonation determines a high seismic hazard level for the city of Sulmona and neighboring villages. The present work focuses on the geotechnical characterization of lacustrine soils cored and sampled hundreds of meters deep. The shear wave velocity rofile and the cyclic nonlinear properties in the lacustrine sediments have been determined. A stiffness-depth relation from cyclic laboratory tests is derived and calibrated with available in-hole tests. Results have been integrated with VS profiles from 2D seismic arrays that constrained the whole thickness of fluvio-lacustrine sediments. A validation of the Vs profile has been finally realized by comparing computed resonance frequencies with xperimental values derived from HVSR analyses on microtremor measurements. We present a geological cross-section, selected to investigate the seismic response through 2D numerical analysis in the 3rd level of the seismic microzonation study, as a representative eotechnical model of the Sulmona city center.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
