Spatial and Temporal Stress Changes in the Aftershock Sequence Following the Nov. ۱۲, ۲۰۱۷ Sarpol-e Zahab Earthquake

A devastating earthquake with moment magnitude of ۷.۳ hit Sarpol-e Zahab in the Zagros on November ۱۲, ۲۰۱۷. An intense aftershock sequence was recorded by the permanent and dense temporary seismic networks, which installed rapidly in the epicentral region. The focal mechanisms of the November ۲۰۱۷ aftershocks were gathered (for about ۵۰ events) and derived (for about ۱۰ events) from P-wave polarities and/or waveform modeling, show predominantly thrust movements. The transpressional stress regime in the region is suggested as the driving force for the earthquakes. The temporal variation of the principal stress directions analyzed by subsequent stress inversion in several time intervals following the Nov. ۲۰۱۷ mainshocks. In addition, the spatial stress variations were studied implementing the stress tensor inversion in different clusters of events. These results suggest that the ۲۰۱۷ mainshock ruptures caused both spatial and temporal stress perturbations that continued in time showing a specific character, which was not observed before in the Zagros region.

Keywords:

Earthquake , Focal mechanism , Inversion , Sarpol-e Zahab , Spatial , Stress , Temporal