Focal mechanism determination based on the polarity and SV-P amplitude ratio in the Kalabsha area, Aswan, Egypt
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Focal orientations are presented for small earth-quakes of the four different local seismic zones (zone A, zone B, zone C and zone D) in the Kalabsha area, Aswan, Egypt. These earthquakes (1.2≤M<3, and depth 1.5-23km) were monitored by the Aswan Telemetered Network between November 1995 and November 1997. Three or four single-event focal mechanisms and one composite event focal mechanism were determined for each zone. One composite focal mechanism for all events of the zones A, B, and C (10 earthquakes) was obtained. Both P-wave polarities and SV/P amplitude ratios were used to determine the focal mechanisms in the study area. The focal mechanism solutions in the four seismic zones show that they are almost characterized by strike-slip faults with two types of motion, right lateral along ENE-WSW faults and left lateral motion along NNW-SSE faults. The orientations of the compressional and tensional stresses prevailing in the area have the directions of ESE-WNW and NNE-SSW, respectively. It is found that there is no significant change in either the direction of prevailing stresses or the senses of motion along the preexisting faults in the area.
Key wordsfocal mechanism P-wave polarity SV/P amplitude ratio Kalabsha area strike-slip motion
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