Semi-empirical relationships to assess the seismic performance of slopes from an updated version of the Italian seismic database

Abstract

Seismic performance of slopes can be assessed through displacement-based procedures where earthquake-induced displacements are usually computed following Newmark-type calculations. These can be adopted to perform a parametric integration of earthquake records to evaluate permanent displacements for different slope characteristics and seismic input properties. Several semi-empirical relationships can be obtained for different purposes: obtaining site-specific displacement hazard curves following a fully-probabilistic approach, to assess the seismic risk associated with the slope; providing semi-empirical models within a deterministic framework, where the seismic-induced permanent displacement is compared with threshold values related to different levels of seismic performance; calibrating the seismic coefficient to be used in pseudo-static calculations, where a safety factor against limit conditions is computed. In this paper, semi-empirical relationships are obtained as a result of a parametric integration of an updated version of the Italian strong-motion database, that, in turn, is described and compared to older versions of the database and to well-known ground motion prediction equations. Permanent displacement is expressed as a function of either ground motion parameters, for a given yield seismic coefficient of the slope, or of both ground motion parameters and the seismic coefficient. The first are meant to be used as a tool to develop site-specific displacement hazard curves, while the last can be used to evaluate earthquake-induced slope displacements, as well as to calibrate the seismic coefficient to be used in a pseudo-static analysis. Influence of the vertical component of seismic motion on these semi-empirical relationships is also assessed.

Probabilistic assessment of seismic-induced slope displacements: an application in Italy

“…Hazard curves and maps are developed for different zones of the Italian territory and the main factors affecting the results are critically analysed. The results have been obtained using the ground motion database described by Gaudio et al (2020), that provide details on the seismic events considered in the analyses. According to Gaudio et al (2020), the permanent displacements are computed with the rigid sliding-block model (Newmark 1965) for the simple scheme of an infinite slope assuming a constant shear strength, that is a constant k y , during earthquake loading.…”

“…The results have been obtained using the ground motion database described by Gaudio et al (2020), that provide details on the seismic events considered in the analyses. According to Gaudio et al (2020), the permanent displacements are computed with the rigid sliding-block model (Newmark 1965) for the simple scheme of an infinite slope assuming a constant shear strength, that is a constant k y , during earthquake loading. Computation have been carried out for different values of the yield seismic coefficient, using an updated version of the Italian strong motion database.…”

“…Furthermore, Bray et al (2018) highlighted the importance of differentiating displacement models depending on the tectonic setting. Gaudio et al (2020) derived semi-empirical relationships for the Italian territory by performing a parametric integration of an updated version of the Italian seismic database, along the line tracked by Rampello et al (2010) and Biondi et al (2011). The database includes 954 records of 208 seismic events with moment magnitude M w ≥ 4, peak ground accelerations PGA ≥ 0.05 g, epicentral distance R ep < 100 km recorded by 297 stations located throughout the national territory referred to a temporal period ranging from 14/06/1972 to 24/04/2017, thus including the seismic records of the recent destructive earthquakes occurred in 2009 L'Aquila (Maugeri et al 2011), 2012Emilia (Mucciarelli and Liberatore 2014 and 2016 Central Italy seismic sequence (Mollaioli et al 2019;Luzi et al 2019).…”

“…For each station, information about the subsoil class is available according to the classification provided by Eurocode 8, Part 1 (CEN 2003) and by the Italian Building Code (Ministero delle Infrastrutture 2018). Gaudio et al (2020) also provide information on the tectonic setting of the seismic database: 581 events (61.3% of the total) are characterised by a normal focal mechanism (NF), while the registrations with reverse (TF), oblique reverse (U) and strike-slip (SS) fault mechanisms are 170 (18%), 126 (13.3%) and 65 (6.9%), respectively. Therefore, based on the number of records, the most relevant mechanism in this study is the normal fault.…”

“…Both scalar and vector probabilistic approaches are employed: in the first case the peak ground acceleration (PGA) is used as ground motion parameter, while the combination of PGA with the peak ground velocity (PGV) is chosen for the vector approach. Although Cho and Rathje (2020) and Gaudio et al (2020) demonstrate that the best double-parameters models are obtained for the couples Arias intensity and mean period (I A , T m ) and (I A , PGV), the couple of parameters PGA, PGV is here adopted because: (i) the ground motion prediction equations (sometimes denoted in the literature as attenuation laws) entering the probabilistic method are generally available only for PGA and PGV; and (ii) the standard seismic probabilistic hazard analysis (PSHA) is commonly developed in terms of peak ground acceleration.…”