Physical stratigraphy and geotechnical properties controlling the local seismic response in explosive volcanic settings: the Stracciacappa maar (central Italy)

Abstract

Nowadays, policies addressed to prevention and mitigation of seismic risk need a consolidated methodology finalised to the assessment of local seismic response in explosive volcanic settings. The quantitative reconstruction of the subsoil model provides a key instrument to understand how the geometry and the internal architecture of outcropping and buried geological units have influence on the propagation of seismic waves. On this regard, we present a multidisciplinary approach in the test area of the Stracciacappa maar (Sabatini Volcanic District, central Italy), with the aim to reconstruct its physical stratigraphy and to discuss how subsoil heterogeneities control the 1D and 2D local seismic response in such a volcanic setting. We first introduce a new multidisciplinary dataset, including geological (fieldwork and log from a 45-m-thick continuous coring borehole), geophysical (electrical resistivity tomographies, single station noise measurements, and 2D passive seismic arrays), and geotechnical (simple shear tests performed on undisturbed samples) approaches. Then, we reconstruct the subsoil model for the Stracciacappa maar in terms of vertical setting and distribution of its mechanical lithotypes, which we investigate for 1D and 2D finite element site response analyses through the application of two different seismic scenarios: a volcanic event and a tectonic event. The numerical modelling documents a significant ground motion amplification (in the 1–1.5 Hz range) revealed for both seismic scenarios, with a maximum within the centre of the maar. The ground motion amplification is related to both 1D and 2D phenomena including lithological heterogeneity within the upper part of the maar section and interaction of direct S-waves with Rayleigh waves generated at edges of the most superficial lithotypes. Finally, we use these insights to associate the expected distribution of ground motion amplification with the physical stratigraphy of an explosive volcanic setting, with insights for seismic microzonation studies and local seismic response assessment in populated environments.

Ground motion prediction maps using seismic-microzonation data and machine learning

“…The damage pattern induced by seismic events is related to both geological/geomorphological conditions and the vulnerability of structures and infrastructures (Brando et al, 2020;Fayjaloun et al, 2021;Mori et al, 2020bMori et al, , 2019. The ground motion prediction (i.e., seismic site response) is generally evaluated by means of numerical simulations which are time consuming and require well-detailed models capable of properly representing subsoil and topographic conditions (see, for example, Bouckovalas and Papadimitriou, 2005;Falcone et al, 2020aFalcone et al, , b, 2018Gatmiri and Arson, 2008;Gazetas, 1982;Luo et al, 2020;Moscatelli et al, 2020b;Pagliaroli et al, 2014;Pitilakis et al, 1999;Régnier et al, 2016Régnier et al, , 2018.…”

Effects of Earthquake on Behavior Characteristics of Fault Gouge in Time-History Analysis of Slope

“…Cong et al [19] explored the boundary effects on the seismic response of a three-dimensional (3D) slope and concluded that an increase in the PGAs of earthquake events tends to enlarge the difference among the three lateral boundaries, whereas the differences between the three lateral boundaries are small for an earthquake with a larger predominant period. Moscatelli et al [20] studied the effect of stratigraphy and geotechnical properties on the seismic response in an explosive volcanic setting and reported that the occurrence of alternating soft and stiff materials in the central part of the maar strongly increases the site amplifications occurring at the surface.…”