Modelling site response at regional scale for the 2020 European Seismic Risk Model (ESRM20)

Abstract

Quantitative estimation of seismic risk over a region requires both an underlying probabilistic seismic hazard model and a means to characterise shallow site response over a large scale. The 2020 European Seismic Risk Model (ESRM20) builds on the 2020 European Seismic Hazard Model (ESHM20), requiring additional information to firstly parameterise the local site condition across all of Europe, and subsequently determine its influence on the prediction of seismic ground motion. Initially, a harmonised digital geological database for Europe is compiled, alongside a model of topographic/bathymetric elevation and a database of 30 m averaged shearwave velocity measurements ($$V_{S30}$$ V S 30 ), in order to produce separate 30 arc-second maps of inferred $$V_{S30}$$ V S 30 based on topography and on geology. We then capitalise on a large database of seismic recording stations in Europe for which site-to-site ground motion residuals ($$\delta S2S_{S}$$ δ S 2 S S ) have been determined with respect to the shallow crustal ground motion model used in the ESHM20. These residuals allow us to incorporate site amplification functions into the European GMM calibrated upon either observed or inferred $$V_{S30}$$ V S 30 , or on the European geology and topography models. We present the resulting pan-European seismic site amplification model and assess its impact on seismic hazard and risk compared against other approaches. The new site amplification model fulfils the requirements of the ESRM20 and, providing uncertainty is fully propagated, yields estimates of seismic hazard and risk at a large space scale that may be comparable to other methods often applied at local/urban scale where better-constrained site information is available.

Exploring inferred geomorphological sediment thickness as a new site proxy to predict ground-shaking amplification at regional scale: application to Europe and eastern Türkiye

“…Thompson et al, 2014;Vilanova et al, 2018;Foster et al, 2019;Mori et al, 2020;Li et al, 2022). However, as also argued by Weatherill et al (2020Weatherill et al ( , 2023, the main purpose of V S30 is as a proxy to predict site amplification, and when inferring V S30 from other parameters, it thus becomes a proxy of a proxy. In fact, site amplification predicted by V S30 based on slope shows little improvement to the site-amplification models based directly on slope (Weatherill et al, 2020).…”

“…For larger areas and regional site-amplification analysis, however, the site conditions must be derived from empirical relations between relevant proxies available through regional or global maps (e.g. Bergamo et al, 2022;Thompson et al, 2010;Weatherill et al, 2023). Currently, the common practice for characterizing site amplification in seismic hazard and risk assessment is using the average shear wave velocity of the upper 30 m of the soil column (V S30 ).…”

“…In fact, site amplification predicted by V S30 based on slope shows little improvement to the site-amplification models based directly on slope (Weatherill et al, 2020). Furthermore, it is important to keep in mind that inferred V S30 should not be used interchangeably with measured V S30 values without properly accounting for the additional uncertainty related to the V S30 calculations (Lemoine et al, 2012;Thompson and Wald, 2016;Weatherill et al, 2023). The variability of ground motion predictions can have great impact on the resulting probabilistic seismic hazard and risk assessments.…”

Large-scale damage assessment of buildings considering SSI and site amplification: The case of Thessaloniki

“…These factors are defined by soil categories that can be identified based on the shear wave velocity in the upper 30 m of the soil column ( V S , 30 ) from microzonation studies or on V S , 30 maps derived from proxies, such as local topography (Wald and Allen, 2007) or geolithology (Forte et al, 2017). A comprehensive overview can be found in the study by Weatherill et al (2023). Spectral transfer functions, in which each spectral ordinate intensity level is multiplied by the appropriate value of the amplification factor, can, however, better account for the dynamic response of the soil and thus for the amplification effects on risk analysis (Sálgado-Galvez et al, 2014).…”

Updating proxy-based site amplification map with in-situ data in Osaka, Japan: A Bayesian scheme based on uncertainty projected mapping

“…In the United States, the United States Geological Survey (USGS) has published a map with measured Vs30 values from borehole data and ambient vibration studies funded by USGS and other governmental agencies (McPhillips et al, 2020). In Europe, a publicly available measured Vs30 values database was published as part of the European Seismic Risk Model (ESRM20; Weatherill et al, 2022). In Japan, in addition to the borehole data available at the strong motion seismograph network of K-NET and KiK-net (National Research Institute for Earth Science and Disaster Resilience, 2019), the Ministry of Land, Infrastructure, Transport and Tourism (MLIT), the Public Works Research Institute (PWRI) and the Port and Airport Research Institute (PARI) also maintains a public database of borehole data compiled from different projects all over Japan (Kunijiban, 2008).…”