Multi-Scale Seismic Hazard Assessment for Egypt

Egypt is a country with mainly moderate seismicity; it has witnessed strong earthquake impacts along its long history from far-field sources and earthquake impacts from the local. The occurrence of these destructive earthquakes ensures the importance of carrying out a reliable and comprehensive characterization of expected seismic ground shaking, which is essential in order to develop effective seismic mitigation strategies and increase earthquake preparedness for Egypt. So, reliable seismic hazard maps that computed based on correct data and methodology should be prepared for building codes applications; also these maps should be updated when needed. In the first chapter of this thesis, a review of the existing seismic hazard for Egypt is performed. For the understanding and studying the development of seismic hazard studies for Egypt, we had collected and tested the existing SHA maps, computed at different scales, against the available observations and physical assumptions, data quality, and methodology. Then, we propose some suggestions that could be considered before new seismic hazard maps can be produced and then adopted, for the real benefit of society. In Chapter 2, an update of seismogenic zones and nodes has been performed, which is needed to perform an updated seismic hazard study for Egyptian territory. We think that the incorporation of seismogenic nodes information side by side with the updated seismogenic zones in the seismic hazard computation may improve performance and usefulness of the resulting maps for the studied region, especially for the sites that have been silent in during the earthquake catalog window show no seismic activity in the catalog so far. Chapter 3 provides an update for the seismic hazard maps available for Egypt that incorporates recent studies, such as reviewed historical earthquake catalogs, morphostructural zonation data (MZ), revised fault plane solutions and laterally non-varying crustal structure using the neo-deterministic seismic hazard assessment (NDSHA) procedure. Also, a sensitivity analysis of different ground motion maps computed adopting different (a) models for the earthquake source process, (b) crustal structure models of the crust and (c) mapmaker’s preconceptions (e.g., different seismotectonic models), is provided. In Chapter 4, detailed ground motion modeling for the proper characterization of the amplification patterns (site-effects) along three 2D profiles have been accomplished. The expected amplification patterns range between 2 and 5 and occur at a frequency range 1-7Hz based on the location of the site along the profiles, subsurface geometry and the thickness of the sedimentary layer. In Chapter 5, we provided the seismic input (response spectra and time histories) that can be applied for the proper evaluation of the dynamic performance of the minaret of the Madrasa the Princess Tatar al-Higaziya, which by role will help in proposing a seismic conservation strategy for this valuable structure. A detailed numerical model for the minaret was established, accompanied with installing ambient sensors for calibrating the numerical model. The careful assessment of the seismic excitation on the historic minaret through conducting the proposed C-MCSI response spectrum and time history analyses predicts severe damage to the minaret: significant lateral displacements at the minaret top and excessive tensile stress concentration, particularly at the geometric transition zone between the squared base and the hexagon shaft, have been developed. Since the minaret is expected to suffer severe damage against the anticipated scenario of earthquake shaking, a vital protection plan is recommended for the minaret to avoid any future damage or collapse.