Seismic microzonation of a region with complex surficial geology based on different site classification approaches

Abstract

A seismic microzonation study was conducted to refine the seismic hazard model for the city of Saguenay, Canada. The Quaternary geology underlying Saguenay shows complex glacial and post-glacial stratigraphy with a number of buried valleys filled with fluvioglacial and glaciomarine sediments. High impedance contrast between rock formations and surficial sediments is prone to seismic amplification. To evaluate their applicability, advantages and limitations in capturing the geological specificity of the study area, four site classification methods were applied: the current National Building Code of Canada (NBCC) and Eurocode 8, both mainly based on the average shear-wave velocity for the surficial sediments (VS,avg) and for the top 30 m (VS,30); a method based on the fundamental site period (T0); and a hybrid method based on the combination of VS,30, T0 and VS,avg. The study specifically aimed to evaluate the importance of the site classification parameters on the resulting microzonation maps. VS,30 is capable to present the geological and geotechnical site conditions, however, the results may be further improved by considering Vs,avg in shallow and T0 in thick layers of soil sediments as secondary parameters. The T0 method gives also satisfactory results with T0 showing a better correlation to Vs,30 than to Vs,avg. The versatile hybrid method may be challenging to apply in certain cases with its nine different site categories and parameters.

Developing effective subsoil reference model for seismic microzonation studies: Central Italy case studies

“…Several seismic microzonation procedures have been applied worldwide in the last years (e.g, Thitimakorn, 2019;Molnar et al, 2020;Régnier et al 2020;Salsabili et al, 2021;Mase et al, 2021) by considering both geological and geophysical/geotechnical information to constrain expected amplification effects. In most cases, engineering geological information plays a minor qualitative role and no specific protocol is defined to standardize its implementation in microzonation studies.…”

Seismic microzonation mapping of Greater Vancouver based on various site classification metrics

“…There are fewer seismic microzonation maps in Canada based on site period (inverse of f 0 ): Toronto (Mihaylov, 2011) and Québec City (Leboeuf et al, 2013). More recent Canadian seismic microzonation studies have produced multiple maps of various seismic site characterization measures, including site period (V Sav , Vs 30 , or both; not NBC site class) and total sediment thickness maps with the development of 3D geomodels: the St. Lawrence Lowlands (Nastev et al, 2016) and Saguenay, QC (Salsabili et al, 2021). The ongoing Metro Vancouver seismic microzonation mapping project (Molnar et al, 2020) will produce a suite of high-quality (grade III) seismic microzonation maps to convey local seismic site conditions (e.g., Vs 30 , site period, and post-glacial/glacial sediment thickness) and probabilistic seismic hazard maps depicting shaking (de)amplification and seismic-induced liquefaction and landslide hazard potential at 2% and 10% probability of exceedance in 50-year risk levels (considering ground motions with a 2,500-and 475-year recurrence interval, respectively).…”

Seismic Hazard and Site Suitability Evaluation Based on Multicriteria Decision Analysis

“…To reduce the aforementioned effects, certain physical and/or geological parameters of surface or subsurface rocks in urban areas and their vulnerability to earthquake hazards should be effectively considered beforehand [8], [9]. As a result, a procedure for shortlisting sites is needed to pick the most ideal places for applying site-specific micro zonation methods [10]- [12] nature-based seismic hazard reduction measures.…”