Full length articleSpatial variation in the frequency-magnitude distribution of earthquakes under the tectonic framework in the Middle East

- The seismic b-value and energy release are spatially mapped within the Middle East region.
- We found that central Zagros, Cascadia, and Hindu-Kush have high b-values.
- Within the Zagros b-values decrease from northwest to southeast.
- A strong low b-value anomaly was observed at the major tectonic discontinuity at Strait of Hormuz.

Spatial variations of seismic energy released and b-value over the Middle East region are investigated based on a seismicity catalog from 1995 to 2007. The goal is to use these seismic parameters and based on other geodetic and geophysical observations, such as GPS measurements, strain rate model, fault distribution, focal mechanism, crustal model, Q model, and gravity measurements, etc., to uncover spatial patterns that seem anomalous. Areas of high energy released (cumulative) seem to correspond to the areas of relatively high b-values. Areas of high energy released and high b-values seem to correspond very well with the location of continental collision where earthquake activities are high. The divergent boundary between Arabia and African plates and subduction zone at Makran seem to correspond to low to moderate energy release.Northern Pamir, Azerbaijan-Caucasus, the lower part of Zagros Mountains, eastern Turkey, Owen Fracture Zone, Strait of Bob-el-Mandeb, and south of the Sulaiman Shear Zone seem to correspond to high cumulative energy-released, high strain rate, high b-values, and high fault density. While, the central and eastern Iran, southern Zagros, northern Pakistan, Gulf of Aden, Alborz, southwest of the Caspian Sea, western Caucasus and Kopeh-Dagh seem to correspond with lower b-values.The cross-section map for Hindu-Kush shows general decreasing of the b-values with depth, however, a region of high b-value is observed underneath Pamir at depths from 170 to 230 km. This anomaly region can be due to dehydration of Pamir crustal slab at depth.

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