Shahrokh Pourbeyranvand - International Institute of Earthquake Engineering and Seismology (IIEES) Tehran, Iran
Mohammad Tatar - International Institute of Earthquake Engineering and Seismology (IIEES) Tehran, Iran

The Alborz is one of the most important seismotectonic provinces in Iran from seismicity point of view. Furthermore, emplacement of Tehran as a mega city in southern part of the Alborz intensifies the seismic vulnerability in this area. In this study the focal mechanism data from teleseismic data sources (GCMT) and local seismic networks has been used for stress tensor inversion. The earthquake focal mechanisms in the Central Alborz are clustered with respect to their location. Focal mechanism stress tensor inversions for each subdivision of data show spatial variations in tectonic stress field. The central Alborz can be divided to western and eastern parts based on above facts. The deformation can be observed by shortening on northern and southern reverse faults and left-lateral strike-slip motion in central parts. The observed strike slip motion can be described by deformation partitioning due to act of regional stresses on preexisting weak planes in the area.

Deformation partitioning, focal mechanism, inversion, Stress