Ground motion prediction equations for Algeria and surrounding region using site classification based H/V spectral ratio

Abstract

The present work is exclusively based on recorded data provided by the Algerian and the European strong ground-motion database. These data contain 1391 records homogeneously processed with more than 700 records in Algeria and the rest from essentially the Mediterranean region, with distance and magnitude ranging from 5 to 150 km and 3.0 to 7.4 respectively. An emphasis is given to the proposal of appropriate ground motion prediction equation (GMPE) for Algeria and surrounding region considering site classification. This latter is based on the predominant period computed using average horizontal to vertical spectral ratio response (H/V). Four site categories are defined according to Zhao et al. (Bull Seismol Soc Am 96:914–925, 2006) classification scheme. Due to the insufficient number of records for very soft soil, one considers three soil classes for the computation of the empirical predictive spectral ground motion relations: rock, firm and soft. Two cases are studied; the first one considers only local data (52.84% with 3.0 ≤ M ≤ 6.8) which serves to illustrate the limits of considering only the country’s borders, while in the second case, the regional data is added (47.16% with M ≥ 5.2) to investigate its influence on the reliability and the robustness of the developed model. A truncation distance criteria is applied with respect to the magnitude and the distance values associated with each data. The obtained results show that (1) the model based on local data overestimates the predicted accelerations for larger magnitude, while the model based on regional data is in good agreement with the last published models; (2) among the four soil classes, the amplitudes and the shapes of the mean H/V spectral ratios are significantly different. Furthermore, the peaks in the period range are reasonably similar to those of site periods defined for each site class by Zhao et al. (2006); (3) the standard deviation decreases compared to the original rock/soil classification scheme and the obtained mean site coefficients for stiff and soft soil are in good agreement compared to those defined in EC-8 (CEN, Eurocode 8, design of structures for earthquake resistance—part 1: general rules, seismic actions and rules for buildings. EN 1998-1: 2004. Comite Europeen de Normalisation, Brussels, 2004); (4) at short distance, the proposed GMPE for Algeria predicts relatively smaller spectral acceleration compared to recent published models possibly due to the differences in the lower magnitude bounds of these models; (5) in addition to the proposed model, this study makes in evidence that Boore et al. (Earthq Spectra 30:1057–1085, 2014) and Akkar et al. (Bull Earthq Eng, 2013. https://doi.org/10.1007/s10518-013-9461-4 ) models are appropriate for the computation of the seismic hazard in Algeria.