CHARACTERISTICS OF SURFACE RUPTURE OF EL ASNAM (ALGERIA) EARTTHQUAKE AND THE STUDY OF PALEOSEISMIC EVENTS

The Main rupture of the El Asnam M=7.5 earthquake is characterized by compression-shearing. A series of parallel or oblique secondary extensional fractures developed on the thrusted wall and the trail of the fault. The main fracture zone was 36 km in length,with vertical dislocation of 1.5-2 m and horizontal dislocation of 1.5 m.Many evidences for paleoearthquake and paleo-dislocation have been found all along the seismic rupture zone. Based on the measurements and comparison analysis of various parameters of dislocations. It is determined that the recurrence interval of earthquake with similar magnitude,in the same area is about 596 years.