Shallow Earthquake Sources in Iran

Session: Alpine-Himalayan Alpide Shallow Earthquakes and the Current and the Future Hazard Assessments
Type: Oral
Date: 4/30/2020
Time: 01:45 PM
Room: 215 + 220
Description: 

Iran is one of the seismically most active regions along the Alpine-Himalayan belt. High seismicity is due to the Arabia-Eurasia plate convergence, which is accommodated within wide deforming zones. The deformation causes magnitude M=6 and larger earthquakes almost each year often associated with significant destruction and loss of life. We use broadband, 3-component waveforms from in-country seismic networks to determine the seismic moment tensor and centroid depth of Iranian earthquakes from 2004 to 2019 with a magnitude of completeness (M_c) near 4.2-4.3 since 2013. Lower-crustal and sub-crustal earthquakes, with few exceptions, are confined to the Makran subduction zone (east of 56°E and south of 30°N) and the Caspian Sea area. Otherwise, most (>80%) centroids are shallow (≤12 km depth) indicating ruptures in the upper crust. This includes the majority of M6+ earthquakes. Even though shallow, most of them did not produce surface faulting and occurred along previously unknown or ill-defined faults, which has to be considered for future hazard assessments. This includes the 2013 M6.5 Khaki and 2014 M6.2 Mormori events in the Simply Folded Belt (SFB) of the Zagros Mountains, the 2017 M6.0 Fariman earthquake in NE Iran, the 2010 M6.5 South Rigan event in southeast Iran and the 2013 M6.2 Minab sequence above the Makran subduction zone. The 2017 M7.3 Ezgeleh main shock in the SFB ruptured on a shallow-dipping basement fault precluding surface rupture. The shallow nature of faulting and the almost country wide distribution of active faults capable of destructive M6+ earthquakes leads to high seismic hazard in Iran.

Presenting Author: Jochen Braunmiller

Authors