Attenuation of intensity in the northern part of Egypt associated with The May 28, 1998 Mediterranean earthquake
On May 28, 1998, a moderate size earthquake of magnitude 6 occurred at lat, 31.45°N; long. 27.63°E. It was strongly kit in the northern part of Egypt. This study presents its intensity distribution based on the field observations and 280 MMI questionnaires describing the situation in the northern part of Egypt immediately after the mainshock. These reports indicate that this earthquake caused a strong shaking in Cairo and in many localities along the Nile Delta area. Cracks on buildings were observed in several places in Mersa-Matruh province, the western area of the Mediterranean Sea coast in Egypt, but cracks on ground were only observed on the sea beach area of Ras E1-Hekma village. Based on these data, the intensity-distribution map is presented here; its isoseismals are of non uniform distribution. The attenuation of MM intensity (I) with epicentral distance (D in km) of the studied shock is determined using a simple relation of type log I = log Io - mD, where Io is the epicentral intensity and m is constant. According to the variation in m constant, the isoseismal map of the studied area is divided into two zones, (a) and (b) of which zone-a is characterized by a higher m. The interpretation of the remarkable change in the m-value is attributed to the obvious variations in geological structures between zone-a and zone-b.
Bibliogr. 21 poz.