SPATIAL VARIBILITY OF CPT DATA FOR LIQUEFACTION ASSESSMENT

The seismic liquefaction is often responsible for the major part of the economic losses caused by earthquakes. Usually damages involve the foundations of buildings, bridges, embankments, underground constructions and are widely diffused over the cities. The strategies for the mitigation of risk aim to evaluate susceptibility and hazard on given areas by quantifying the liquefaction potential indexes from the results of fast investigations. The empirical relations proposed in the literature based on the results of cone penetration tests CPT, allow to calculate the indexes at each vertical, which can be reductive for the complete risk assessment of larger territorial extension. The present study moves at two distinct levels, one carried out with traditional geographic information systems aiming to map the liquefaction hazard over the territory, the second one aiming to define the three-dimensional distribution of the liquefiable deposit in the subsoil.
The analysis focuses on the district of San Carlo, in the municipality of Sant’Agostino (Italy), located near the epicenter of the 2012 Emilia Romagna earthquake (Mw = 6.15). Several dozens of CPT profiles have been processed to compute the liquefaction potential maps and the individuation of the liquefiable deposits, using geostatistical methodologies. The results, validated with the observations of ground failures and damaged buildings recorded after the earthquake and with the geological structure of the investigated area, improve the quality of Microzonation studies with the addition of the liquefaction hazard and helps to precisely identify the susceptible subsoil deposit.