SARCA
Evaluation of the local seismic response in the lower Sarca Valley on the northern shore of Lake Garda
The three-year project, co-financed by the Autonomous Province of Trento, aimed to evaluate the local seismic response (LSR) in the lower Sarca Valley on the northern shore of Lake Garda.
But what is LSR? It is the influence of the geological and morphological characteristics of a site on the seismic shaking induced by an earthquake. In complex contexts, such as Alpine valleys, ground motions can experience significant amplification due to the resonance effect of the sediments filling the valley and the physical configuration of the valley itself (2D-3D effects).
Through these studies, it is possible to gain a detailed understanding of the seismic behavior of the area, leading to a more accurate assessment of the seismic hazard. This is crucial for the development of third-level seismic microzonation studies used in urban planning and, more recently, in engineering design.
The analysis of LSR is based on an integrated approach that combines direct estimates from experimental data (ambient seismic noise and earthquake recordings) with theoretical estimates derived from numerical simulations using physical models of the subsurface.
The project is the result of a collaboration between the Seismological Research Center (CRS) and the Geological Service of the Autonomous Province of Trento.
The activities include:
- Installation of a temporary seismometer network to record seismic events and collecting ambient seismic noise;
- Estimation of the LSR through integrated processing of the recorded data;
- Performing gravimetric and seismic array surveys to create a 3D geological and geophysical model of the buried valley;
- Three-dimensional numerical modeling of ground motions to obtain detailed estimates of the local seismic hazard.
The results of the investigations have revealed significant seismic amplification effects within the valley, related to the complex geological context of the lower Sarca Valley. Three zones with different characteristics of the local seismic response have been identified, characterized by significant ground motion amplification factors that need to be considered in an appropriate assessment of the seismic hazard of the area.