BENI ILLMANE EARTHQUAKE OF MAY 14, 2010 - AFTERSHOCK SEQUENCE LOCATION
USING A DENSE SEISMIC NETWORK.
Supervisor: Nobuo HURUKAWA
The Beni-Illmane earthquake sequence, which started on May 14th, 2010, occurred in a region of low to moderate seismic activities in north Algeria. Following the first main shock, the National Center of Applied Research in Earthquake Engineering (CGS) acted and organized a seismic survey of aftershocks using 13 temporary seismic stations installed close to the epicentral area during 30 days recording period. The data was analyzed by using the Seisan program and the phase picking was performed for 14 days including the third main shock on May 23rd (Md = 5.0). A subset of 406 aftershocks was used to resolve details of the hypocenter distribution. . The VP/VS ratio was calculated by using both Wadati diagram and Chatelain method and was estimated to 1.74. We relocated 141 earthquakes precisely using the Modified Joint Hypocenter Determination (MJHD) method and calculated a composite focal mechanisms solution. It appeared a major clusters oriented NNE-SSW with 12.5 km length and the foci were distributed in the two clusters on a near-vertical plane, mostly at depths of 0-5 km and 6-15 km. The composite focal mechanism shows strike-slip faulting with NW-SE compressional axis, which were consistent with previewed studies in the north Algeria.