Correlations of spectral accelerations in the Chilean subduction zone

Abstract

<jats:p> The correlation between spectral accelerations is key in the construction of conditional mean spectra, the computation of vector-valued seismic hazard, and the assessment of seismic risk of spatially distributed systems, among other applications. Spectral correlations are highly dependent on the earthquake database used, and thus, region-specific correlation models have been developed mainly for earthquakes in western United States, Europe, Middle East, and Japan. Correlation models based on global data sets for crustal and subduction zones have also become available, but there is no consensus about their applicability on a specific region. This study proposes a new correlation model for 5% damped spectral accelerations and peak ground velocity in the Chilean subduction zone. The correlations obtained were generally higher than those observed from shallow crustal earthquakes and subduction zones such as Japan and Taiwan. The study provides two illustrative applications of the correlation model: (1) computation of conditional spectra for a firm soil site located in Santiago, Chile and (2) computation of bivariate hazard for spectral accelerations at two structural periods. </jats:p>

Within‐event spatial correlation of peak ground acceleration and spectral pseudo‐acceleration ordinates in the Chilean subduction zone

“…On the other hand, for longer periods (e.g., T = 5s), the proposed spatial correlation model is higher than the median of the HM2019 model and closer to the GA2009 and GA2010 models, which were developed for Japanese subduction earthquakes. The large spatial correlations of long-period spectral ordinates observed in this study are also in accordance with the findings of Candia et al, 37 who used a ground-motion database of Chilean earthquakes to develop inter-period correlations of spectral ordinates and found larger correlations than those previously obtained for active shallow crust regions. However, inter-period correlations depend on the frequency content of earthquake ground-motions at a specific site, 37 while spatial correlations are associated to the wave propagation path from source to site, local site effects, and relative location to main fault asperities.…”

“…The large spatial correlations of long-period spectral ordinates observed in this study are also in accordance with the findings of Candia et al, 37 who used a ground-motion database of Chilean earthquakes to develop inter-period correlations of spectral ordinates and found larger correlations than those previously obtained for active shallow crust regions. However, inter-period correlations depend on the frequency content of earthquake ground-motions at a specific site, 37 while spatial correlations are associated to the wave propagation path from source to site, local site effects, and relative location to main fault asperities. 6 Thus, higher values of inter-period correlations do not necessary indicate higher values of spatial correlations.…”

Epistemic uncertainty of probabilistic building exposure compositions in scenario-based earthquake loss models

“…• The subjective selection of the type of spatial cross-correlation model used to generate the GMF carries epistemic uncertainties (Weatherill et al 2015). Although the selected model proposed by Markhvida et al (2018) has been already implemented for subduc-tion earthquakes for the South American context by Markhvida et al (2017), more rigorous practices could include the incorporation of a locally constrained spatial correlation model (Candia et al 2020, study published after the elaboration of our work). Furthermore, it is important to have in mind the simplifications induced by applying generic correlation models without having performed local wave-form analyses (Stafford et al 2019;Schiappapietra and Smerzini 2021).…”

Towards a Sensitivity Analysis in Seismic Risk with Probabilistic Building Exposure Models: An Application in Valparaíso, Chile Using Ancillary Open-Source Data and Parametric Ground Motions

“…Thus, addressing wave propagation studies, which were out of the scope of our work, would profit from the quality of the resultant loss estimates herein presented in the future. On a complementary note which was also out of our scope, it is worth recognising that even if we had used local correlation models for the Chilean subduction zone (such as in [108], published after this study), the use of generic and isotropic correlation models without having performed local wave form analyses in the vicinity of the study area might have induced overestimations in the risk estimates anyway [109].…”