Investigating the strength and trend of seismic anisotropy in the western part of Makran subduction zone and southeast of Iran

Publication date: Available online 6 November 2019Source: Physics of the Earth and Planetary InteriorsAuthor(s): Saeid Rahimzadeh, Ali Moradi, Ayoub KavianiAbstractThe Makran subduction zone, located in southeastern Iran and southern Pakistan, extends approximately 900 km along the Eurasian-Arabian plate boundary, where the Arabian oceanic plate subducts beneath the Eurasian plate. Using broadband seismic data recorded in the western part of Makran in the southeast of Iran, seismic anisotropy was studied to better understand geodynamic processes of this subduction zone. We analyzed shear wave splitting of core-refracted shear-wave phases (SKS, SKKS and PKS) recorded by 17 broadband stations located in the western Makran and southeast of Iran from 542 earthquakes (MW ≥ 6.0) that occurred between 2004 and 2017 at epicentral distances between 90°–145°. Few stations close to the trench line exhibit a trench-perpendicular trend in the west to a trench-oblique trend to the east. The magnitude of splitting delay times suggests a mantle source of anisotropy.Our findings show that the majority of the fast axes of seismic anisotropy at farthest stations in the backarc region are oriented in the NW-SE direction with delay times (created by crust and mantle) varying between 0.8 and 1.3 s. The orientations of these fast directions are almost parallel to surface structural features. For stations near the Minab strike-slip fault system (the transition from the Makran subductio...
Source: Physics of the Earth and Planetary Interiors - Category: Physics Source Type: research