Seismic potential on the northwestern Main Recent Fault (Iran) revealed by InSAR

The Main Recent Fault (MRF) is an important boundary fault that accommodates the oblique convergence motion between the Arabian and Eurasian plates. Several large earthquakes including the 1909 Mb 7.4, 1958-1963 three events with magnitude larger than Mw 6.0, and the 2006 Mw 6.1 earthquake had partly ruptured the central and southeast segments of MRF. However, there is no large earthquake occurred in the northwest segment in the past hundred years. In this study, the interseismic surface deformation was firstly mapped from the Synthetic Aperture Radar (SAR) images observed by the Sentinel-1 satellite. Then, the ununiformed fault slip rate, coupling ratio and locking depth are estimated based on the measured interseismic surface deformation. The results show that the interseismic fault slip rate slightly varies from ~3.7 mm/yr to ~6.1 mm/yr along the MRF. Furthermore, it is also found a gradual increasing extensional component with magnitude of 2-7 mm/yr from Morvarid to Sahneh segments of MRF. In addition, total 9 sub-segments could be divided based on the fault coupling distribution and historical earthquakes in the interest zone. A seismogenic zone is identified from the historical earthquakes, which has a good space consistency with the transition between the significant shallow locking and deep free slip zones. According to the potential seismic magnitude and estimated recurrence interval, it is found that several segments are approaching the end of their interseismic recurrence interval. Meanwhile, one segment (SF-8) may be in the early stage of a new recurrence period due to the recent several large earthquakes and a long recurrence interval.