Temporal distribution, source parameters, and depth discrimination of earthquakes from the Abu Dabbab region, Egypt
Records of earthquakes from the Abu Dabbab region in Egypt, situated about 25 km west of the Red Sea coast, were collected from the Aswan Seismograph Network (ASN). The temporal distribution of these events shows several sequences of the foreshock-main shock-aftershock type. Four such sequence occurred in 1984 and 1985. the slope of the frequency-amplitude relation (b-value) for the four sequences ranges form 1.8 to 2.4, reflecting co-seismic deformation with time in the vicinity of the source area. Source parameters were estimated for ten events from the same area, which occurred between 1998 and 2001 and had magnitude ranging from 3.0 to 4.2.the spectral plateau, corner frequency, seismic moment, source dimension, and stress drop were calculated. A good correlation is found between the logarithm of seismic moment and the local duration magnitude determined by the ASN. The stress drop is not uniform and ranges between 0.1 and 6.8 MPa. In addition, the relative decay of the amplitude of S waves from the Abu Dabbab earthquakes with the epicentral distance is examined from the records of various stations of the ASN. It was found the rater of decay can be divided into two distinct types, related to different paths between the hypocenters and the stations, which in turn indicate different depths of the studied events.
Bibliogr. 22 poz.