In addition, the spatial stress variations were studied implementing the stresstensor inversion in different clusters of events. These results suggest that the 2017 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. | JSEE Vol. 20, No. 2, 2018 Spatial and Temporal Stress Changes in the Aftershock Sequence Following the Nov. 12, 2017 Sarpol-e Zahab Earthquake Shahrokh Pourbeyranvand 1*, Saeed Soltani Moghadam 2, and Abolfazl Komeazi 2 Received: 18/08/2018 Accepted: 29/09/2018 1. Assistant Professor of Seismology, Earthquake Prediction National Center, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran, * Corresponding Author; email: beyranvand@ 2. . Candidate, International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran AB S T RA CT Keywords: Earthquake; Focal Mechanism; Inversion; Sarpol-e Zahab; Spatial; Stress; Temporal A devastating earthquake with moment magnitude of hit Sarpol-e Zahab in the Zagros on November 12, 2017. 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 2017 aftershocks were gathered (for about 50 events) and derived (for about 10 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. 2017 mainshocks. In addition, the spatial stress variations were studied implementing the stress tensor inversion in different clusters of events. These results suggest that the 2017 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. 1. Introduction Major earthquakes have been shown to significantly influence the stress field in the close vicinity of the rupture. The causative stress field has been reported to rotate significantly for some earthquakes.
