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Ibrahim, E. M.
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Ibrahim, E. M.
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- PublicationOpen AccessFault plane solutions of the 1993 and 1995 Gulf of Aqaba earthquakes and their tectonic implications(1997-12)
; ; ; ; ;Abdel Fattah, A. K.; National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt ;Hussein, H. M.; National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt ;Ibrahim, E. M.; National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt ;Abu El Atta, A. S.; Faculty of Science, Geophysics Department, Cairo, Egypt; ; ; The stereographic projection of P-wave first motions for the 3 August 1993 Gulf of Aqaba earthquake, its largest aftershock (16 h 33 min), and for the 22 November 1995 earthquake were constructed using the polarity readings of regional and teleseismic stations. The focal mechanism solutions of the 3 August 1993 mainshock and its largest aftershock represent a normal faulting mechanism with some left lateral strike slip component. The nodal planes selected as the fault imply high similarity in strike and dip. They are related to a local fault striking NW-SE and dipping to the SW. The selected fault planes are in good agreement with the aftershock distribution. For the main shock of the 22 November 1995, the fault plane solution displays the same mechanism (normal faulting with left lateral strike slip component) with a plane striking N-S and dipping to the west. The fault plane is greatly conformable with the direction of the regional tectonics and also with the aftershock distribution. The main trend of the extension stress pattern is in a NE-SW direction, corresponding to the rifting direction of the Gulf of Suez and may be related to the paleostress along the Gulf of Suez and Aqaba during the Middle to Late Miocene.214 462 - PublicationOpen AccessSeismological aspects of the Cairo earthquake, 12th October 1992(2000-06)
; ; ; ; ;Abou Elenean, K. M.; National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt ;Hussein, H. M.; National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt ;Abu El-Ata, A. S.; Faculty of Science, Ain Shams University, Cairo, Egypt ;Ibrahim, E. M.; National Research Institute of Astronomy and Geophysics, Helwan, Cairo, Egypt; ; ; On 12 October 1992 a significant earthquake (MB = 5.8) occurred southwest of Cairo in the vicinity of the Dahshour region. For the mainshock, an average moment release M 0 = 9.70E17 n-m; a fault length = 13.8 km; an average displacement = 0.22 m; a stress drop = 0.760 MPa and maximum spectral magnitude = 5.78 were obtained. Spectral magnitude calculations were used in this analysis. The distribution of the well-recorded aftershocks over 15 months using a temporary seismic network installed immediately after the mainshock shows a zone of concentrated activity. Three composite focal mechanism solutions are constructed, using P wave polarity data for 30 earthquakes. These solutions have a mechanism, involving normal and right lateral strike slip motion along E-W to ENE-WSW trending fault plane. The P-wave polarity data of the individual 30 earthquakes are inverted to determine the stress tensor. The stress field estimated is extensional with s3 in the direction of NNE. The stress pattern determined from the inversion is in good agreement with the one estimated from the three composite fault plane solutions, while the neotectonic situation in Northern Egypt supports ENE-WSW extensional movement. However, the region of study has suffered both extensional tectonic activity of the Northern Red Sea rift zone and the compressional tectonic activity along the Hellenic arc. The inconsistency of the principal tension directions may belong to the interaction between the extensional and compressioal tectonics.202 1111