Seismic modeling of San Donato area of the ancient mining area of Santa Barbara (Toscany – Italy)

Abstract

As part of the environmental impact evaluation of the mining site, this research was conducted to set the rehabilitation plan by the Commissione Tecnica di Verifica dell’Impatto Ambientale, Ministero per i Beni e le Attività Culturali and Regione Toscana. This article presents the results of Local Seismic Response analysis carried out by geotechnical, geological, geomorphological, hydrogeological, and geophysical surveys in order to verify seismic stability conditions in San Donato waste disposal by classifying zones into stable, instable and susceptible to seismic amplification, in the lignite mine district of Santa Barbara located in the central part of Tuscany (Italy) and including a part of the depression of the valley, which extends about 40 km NW-SE, known as the Upper Valdarno. And to be used in environmental impact evaluation by theThe subsoil geotechnical model and its parameters are defined on the basis of a careful campaign of geotechnical and geophysical survey in the area of San Donato, supplemented by other surveys information available in the area of Santa Barbara. The area is characterized by shallow anthropogenic Holocene deposits. These deposits are deposited above fluvial - lacustrine ground of the Upper Valdarno formed by clay and sandy soil that are part of Montevarchi and Castelnuovo synthem with a pre-lacustrine substratum known as “Medium Oligocene – lower Miocene” Sandstone. The results of the Local Seismic Response analysis were compared with simplified approach of NTC (2008). According to the NTC (2008) the comparison indicates that the simplified procedure based on elastic spectrum response defined by the subsoil category (V_S30) tends to underestimate the seismic action and should be used with caution in the presence of Vs inversion with depth.

Keywords: San Donato, Shear wave velocity, Subsoil category, Local seismic response (RSL), Peak ground acceleration, seismic hazard, resonance frequency, amplification.