GNGTS 2023 - Atti del 41° Convegno Nazionale

Session 2.1 GNGTS 2023 Fig. 1. (a) Local setting that can be properly analysed through the bidimensional numerical simulations; (b) the site setting of a complex 3D model. Case study Arquata del Tronto is a small municipality in central Italy that was severely damaged during the 2016-2017 seismic sequence. The distribution of this damage was not homogeneous, suggesting that strong local modifications of earthquake ground motion (i.e., site effects) occur due to stratigraphic and topographic effects. A number of studies have been conducted to identify and explain the LSR in the Arquata del Tronto area. From a geological point of view, the municipality is located on the outer edge of the Apennine chain, in a foredeep area, characterised by the turbidite Laga Formation, composed of alternations of arenitic and pelitic lithofacies, of different thicknesses. In some places they are covered by Quaternary deposits. A 3D digital geological model of the study area was created by integrating the collected surface and subsurface data (Fig. 1.b). According to their geophysical and mechanical properties, the Laga Formation was divided into two lithotypes. The deposits were defined based on their seismic characteristics, and a weathering layer was added to represent the fracturing and alteration surficial layer. Numerical modeling In this work, numerical simulations of seismic wave propagation allow us to observe how local morphological and seismostratigraphic configurations alter ground motion. Both 2D and 3D numerical analyses have been carried out. In order to unify all LSR studies in central Italy, the Seismic Microzonation Center has defined 7 time histories (ISPRA, 2018) to be adopted as a fixed seismic input, spectrum-compatible with the uniform seismic hazard in the 0.1- 1.1 s period band (Tab. 1). Tab. 1: reference accelerograms, used as seismic input, provided by the Seismic Microzonation Center. Station Date Time (UTC) Mw MZ10 30/10/2016 06.40.18 6.5 MZ21 26/10/2016 17.10.36 5.4 ACC 30/10/2016 06.40.18 6.5 CLO 26/10/2016 19.18.06 5.9 CLO 26/10/2016 19.18.06 5.9 MMO 30/10/2016 06.40.18 6.5 T1212 30/10/2016 06.40.18 6.5