Splay Faults in the Makran Subduction Zone and Changes of their Transferred Coulomb Stress

The Makran subduction zone in northeast and the Sumatra subduction zone (Sunda) in the west have been known as tsunamigenic zones of the Indian Ocean. The ۹۹۰ km long Makran subduction zone is located offshore of Iran, Pakistan and Oman. Similar to many subduction zones all over the world, the Makran accretionary prism is associated with an imbricate of thrust faults across the zone, which may rupture due to great earthquakes. Based on some studies, it has been suggested that the presence of young marine terraces along parts of the western Makran, Jask, and Konarak, providing a strong evidence for the occurrence of great thrust earthquakes in the western Makran. Besides, this region might have experienced a strong earthquake in ۱۴۸۳ (Mw=۷.۲). This study uses ۲D seismic reflection data to map the splay faults in the western Makran subduction zone. The result of this interpretation has been presented on map showing the major splay and normal faults, in the south and north, respectively. Furthermore, Coulomb stress changes is calculated along the splay faults, following a hypothetical earthquake (Mw=۷.۲) on the megathrust. The amount of slip that transfers from the plate boundary onto the splay faults during large subduction earthquake and the pattern of slip partitioning between them are calculated. The results show that the slip on Megathrust increases stress in some parts of surrounding areas. Some splay faults are located in these areas that can be loaded in shallow depth and are likely the sources of aftershocks. Since the slip on splay faults has a key significance in generating tsunami, their analysis is an important issue in tsunami risk assessment. It is strongly suggested that the result of this study is used as an input parameter for a comprehensive tsunami hazard modeling in the Makran region.

Keywords:

Subduction zone , Splay faults , Seismic reflection data , Coulomb stress changes