Contribution to Probabilistic Seismic Hazard Assessment and Its Uncertainty for Northeastern Algeria

Abstract

This contribution uses two distinct gridded seismicity models to present a probabilistic seismic hazard assessment for Northeastern Algeria. Both local regional models and the next generation of attenuation (NGA) equations supplied the ground-motion prediction equations (GMPEs) that have been used. A logic-tree approach is applied to depict the epistemic uncertainty, or the uncertainty in the evaluation caused by the lack of knowledge about the model used. Expert judgment associated with the available acceleration recorded data was used to evaluate the weights assigned to each of the distinct GMPEs. In the final stage, the study offers estimated ground-motion parameters for soil classes B, B/C and C (National Earthquake Hazards Reduction Program) with return periods of 475 and 975 years. Along with uniform hazards spectra for the examined soil conditions and return periods, seismic hazard curves for the main cities are also included. Among the computed ground-motion characteristics, the mean horizontal peak ground acceleration values for the B/C soil types in Setif have been estimated to be 0.30 ± 0.05 g and 0.44 ± 0.05 g for the two considered return periods (475 and 975 years), respectively. Using the exceedance and occurrence deaggregation methodologies, for some locations, a deaggregation investigation was also performed in terms of three parameters (magnitude, distance and azimuth) in order to look at how specific sources influenced the hazard level. This has made it possible to identify the earthquake that contributes most in terms of the considered parameters in the specified locations, known as the "control" or "modal" earthquake.