Document Type : Original Research Paper
Authors
1 Associate Professor, Seismological Research Center, International Institute of Earthquake Engineering and Seismology, Tehran, Iran
2 Ph.D. Student, Seismological Research Center, International Institute of Earthquake Engineering and Seismology, Tehran, Iran
Abstract
The V shape kink of the AlborzMountains at its southern end reaches to the Garmsar city located 100 km southeast of Tehran metropolis. We investigated seismicity and seismotectonic features of the Garmsar area by precisely locating of microearthquakes recorded by our local dense seismological network and by the Iranian Seismological Center (IRSC). Our results indicate high seismic activity at the central and western parts of the Garmsar fault. Three computed focal mechanisms revealed compressional movements of the central part of this fault. Very little seismic activity is observed on the Eyvanekey and the Pishva faults. The only computed focal mechanism for the northern hills of the Garmsar fault shows tensional movements in this area, which refers to strain release among the Garmsar and Sorkheh reverse faults. Most of the calculated focal mechanisms in the Garmsar area indicate compressional and strike slip motions with overall P axis direction of 10° to 35°. The calculated P axis with NW-SE trend, close to the Sorkheh fault, is different from the other calculated P axes that show NNE-SSW direction. This is probably due to rotating of structures in this area, as revealed by recent GPS measurements in this region.
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