Update and sensitivity analysis of the neo-deterministic seismic hazard assessment for Egypt

Abstract

The main goal of this work is to provide an update on the seismic hazard maps available for Egypt that incorporates the results of recent studies, i.e. revised historical earthquake catalogs, morphostructural zonation data (MZ), revised focal mechanism solutions and mechanical models of the lithospheric structure. This is done within the framework of the neo-deterministic seismic hazard assessment (NDSHA) procedure that may effectively accommodate any reliable new information to adequately compute the earthquake ground motion maps (i.e. PGA, PGV and PGD). Furthermore, with the set of relevant scenario earthquakes, this work provides a large dataset of synthetic seismograms, particularly important for the areas that suffer from the endemic lack of useful strong motion time histories such as Egypt, setting the base toward detailed and comprehensive seismic microzonation studies. NDSHA aims to supply an envelope value, in other words a value that should not be exceeded, therefore it is immediately falsifiable and verifiable.A sensitivity analysis based on the different ground motion maps, computed adopting different (a) models for the earthquake source process, (b) mechanical models of the crust and (c) mapmaker's preconceptions (e.g. different seismotectonic models), is provided. The maps of difference and ratio between various ground motion maps computed for different variants are shown and discussed in order to explore the influence of using various input models. The results provide the potential users with an adequate spectrum of choices and reliably assess and clearly communicate the possible uncertainties. The availability of a wide spectrum of hazard maps is a prerequisite to supply valuable information for the significant improvement of a seismic code.