North Africa Group for Earthquakes and Tsunami Studies NAGET

Italy

North Africa Group for Earthquakes and Tsunami Studies NAGET

Italy

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Hassan H.M.,National Research Institute of Astronomy and Geophysics | Hassan H.M.,North Africa Group for Earthquakes and Tsunami Studies NAGET | Panza G.F.,China Earthquake Administration | ElGabry M.N.,National Research Institute of Astronomy and Geophysics | ElGabry M.N.,North Africa Group for Earthquakes and Tsunami Studies NAGET
Engineering Geology | Year: 2017

The seismic hazard studies for Egypt have been initiated a long time ago aiming to predict the ground motion parameters at different geographical scales; their review process had been routinely performed due to the increase of available instrumental observations rather than from methodological advances. For the comprehensive understanding of the development of seismic hazard assessment (SHA) studies in Egypt, we properly collect and test the existing SHA maps, computed at different geographic scales, against the available observations, data quality, physical assumptions and adopted methodology. Most of these SHA studies are probabilistic and the mapped ground motion acceleration values have been often largely exceeded by the observed values due to earthquakes occurred after their publication. For each study, we discuss and evaluate the input data, methodology and the results obtained in order to understand the reasons behind the bad performance of the available seismic hazard maps and to avoid such shortcomings in future seismic hazard assessment. Finally, we formulate suggestions that could be considered before new seismic hazard maps are released and then adopted, for the real benefit of society. © 2017 Elsevier B.V.


Hussein H.M.,National Research Institute of Astronomy and Geophysics | Hussein H.M.,North Africa Group for Earthquakes and Tsunami Studies NAGET | Abou Elenean K.M.,National Research Institute of Astronomy and Geophysics | Abou Elenean K.M.,North Africa Group for Earthquakes and Tsunami Studies NAGET | And 9 more authors.
Journal of African Earth Sciences | Year: 2013

Stress field inversion is performed in Egypt on the basis of 219 focal mechanism solutions in the period from 1955 to 2007. For this purpose Egypt is divided into six seismotectonic zones: the northern part of the Gulf of Suez, southern Gulf of Suez, and Gulf of Aqaba, Cairo-Suez district, Dahshour zone and the Aswan Zone. The entire Gulf of Suez is currently under extensional stress field, with NE-SW trending horizontal extension. In the Gulf of Aqaba, the strike-slip regime predominates with sub-horizontal σ1 and σ3 axes trending NNW and ENE, respectively. A normal dip slip with small strike-slip component due to a nearly sub-vertical σ1 and sub-horizontal NNE striking σ3 characterizes Cairo-Suez district and Dahshour zone. Aswan seismic zone shows mainly strike-slip stress regime with a slight extension component (horizontal NW σ1 and NNE σ3). The stress field derived in this study indicates a prevailing tension stress (σ3 horizontal) which agrees well with the general tectonic frame of northeastern African, which is subjected to tensional stresses. Generally, extensional and/or extensional-strike slips are dominating the Egyptian territory. These regimes are compatible with the kinematics of the Red Sea-Gulf of Suez rift and Gulf of Aqaba transform plate boundary. Furthermore, the inferred stress in the present study (SHmin directed NNE-SSW) for the Cairo-Suez, Dahshour, and Aswan areas is similar to the East African Rift stress fields " Congo and Sudan" especially (Bosworth et al., 1992; Delvaux and Barth, 2010), whose origin is attributed to the far field effects of ridge push in the Atlantic and Indian Oceans (Zoback, 1992). © 2013 Elsevier Ltd.

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