Intraplate Earthquakes in Iraqi Western Desert

Abstract

The seismicity of Iraqi western desert was analyzed. During the period from 1900 to 2004, there occurred about 40 events with magnitude Mw ≥ 3.0.The area was inactive before 1970.This may be attributed to quietness of the area and / or to missing of data and the poor coverage for the local and regional seismic stations. The relation between earthquake magnitude Mw and cumulative frequency Nc for the studied area is Log Nc = 3.51 – 0.54 Mw .The spatial epicentral distribution in western desert shows that there are two seismic zone , Zone (I) and Zone (II). Most events were located in and around the Rutbah uplift ( Zone II). The focal depth of most events in the area belongs to the crust. In order to understand the cause of intraplate earthquakes in the western desert, the idea of intraplate seismicity occurs in vicinity of '' stress concentrators" within preexisting zones of weakness is considered. These concentrators are buried intrusions and intersecting faults. It is found that there is a causal association between the seismicity of western desert and the buried intrusions and fault intersections. A better understanding of the seismicity of western desert requires detailed information about stress and strain within the area, crustal structure, continuous geodetic measurements, heat flow data and detailed microearthquakes monitoring.