Seismicity anomalies of the 2003 Bam, Iran earthquake

The Bam earthquake occurred in an area without any historically recorded major earthquake. Based on active tectonics and CMT solutions the area is under the influence of shortening and right-lateral strike-slip faulting. Seismicity is of a shallow crustal type which is mainly distributed within the Koohbanan–Golbaf, Lakarkooh–Shahdad–Gowk fault systems and the terminal sections of Zagros. In order to detect temporal seismicity anomalies before this earthquake we compiled a catalog from the ISC events and then analyzed it for the magnitude of completeness. After declustering this catalog, changes in seismicity were assessed by the z-value test. The temporal variations indicate a relative decrease in z-value before the Bam earthquake. Additional to seismic quiescence and decrease in b-value before the main shock there are pieces of evidence corresponding to increase in triggered background seismicity after this earthquake.

► Decrease in the z-value before the Bam earthquake. ► Seismic quiescence before the Bam earthquake. ► Decrease in b-value before the Bam earthquake. ► Increase in triggered background seismicity after the Bam earthquake.