CORRELATION BETWEEN B-VALUE AND DIFFERENT STYLES OF FAULTING IN THE CASPIAN SEA REGION

The South Caspian Basin is a part of the Alpine-Himalayan seismic belt. This basin is limited from all sides by active earthquake belts. The diversity of the focal mechanism of earthquakes on the margins of this basin shows the complex tectonic activity of the region including strike slip faulting, large and small angle thrusting, and normal faulting. Data analysis shows that the b-value of the Gutenberg Richter Relation is variable in the region and is correlated to faulting style. While the highest b-values belong to the normal events, thrust events have the lowest b-values and Intermediate values mark strike-slip faulting. In the Caspian Sea basin, earthquakes occurring in the Apsheron-Balkhan seismic belt are deep with normal focal mechanism and b-value map shows an overall b-value for this region of about 1.2, whereas in the Talesh, western Alborz and eastern Kopeh Dag, where the dominant faulting mechanism is thrusting, low b-values can be extracted, of approximately 0.5. In the central Alborz and eastern Apsheron-Balkhan, strike-slip faults result in intermediate b-values. This also introduces the b-value as a stress-metre.

Keywords:

Faulting Styles , b-value , Frequency Magnitude Equation , Caspian Sea