Earthquake Hazards Considerations for Iraq

The seismic hazard for the investigated area outlined by longitudes (30º. 00 –49º. 50’) N and latitudes (28º. 50’-38º. 50`) N. Earthquake data for the period 1900-1988 was utilized for the seismicity studies Most earthquakes clustered on the edges of the Zagros-Tauros subduction zones between the Arabian sub continent Plate and the Iranian and Anatolian Plates; in addition to few intraplate type events on the tectonically stable zone to the west. It was found that 95.5%of the events have mb magnitudes range of (4.0-5.5) and that 75.5% of the vents have a focal depth range of (0.0- 50.0) Kms. The (a) and (b) constants of the Gutenberg-Richter recurrence relation gave the values of 6.85 and 0,89 respectively,thus reflecting and intermediate seismicity level. Historical data for the period 1260 B.C. –1900 A.D. were utilized for the historical isointensity determinations.A seismic zoning map was constructed showing four damage zones ranging between less than (III) and (VIII) on the MM scale. A seismicity index map was also constructed showing the areas east of Tigris River to depict the highest seismicity index.Seismic sources were also investigated, where five line sources and four area sources were modeled and their locations and parameters determined. Isoacceleration maps were constructed for the studies area for four return periods of 25,50,100 and 200 years respectively. The acceleration values tend to increase towards the eastern,northeastern and northern direction.The seismic design parameters were studies and seismic design regionalization map was presented showing a value increase towards the east, northeast and north