Seismotectonics and Velocity Structure in the Qeshm Region Based on the Local Dense Temporary Seismic Network Data
By: Farzam Yaminifard, Khaled Hessmai Azar, Mohammad Tatar, Abbas Gholamzadeh
Abstract
The temporary network included 17 stations established in the Qeshm Island in January 2, 2005 after the November 27, 2005 Qeshm earthquake (Mw, 6.0) to record aftershocks. This network stays there until February 25, 2006.
Results shows that the upper crust structure of the southern edge of the Zagros in Qeshm includes a sedimentary layer of thickness 8 km and speed 5.5 km/s on the another layer with 4 km thickness and about 5.9 km/s speed on the another layer with 6.2 km/s. The calculated ratio between Vp and Vs is 1.85.
Epicentral distribution of the aftershocks reveals east-west and northwest-southeast trends of seismicity. An aftershocks depth between of 11 to 18 km implies that they are located beneath sedimentary layer. Depth distribution is diffuse and a trend of seismicity with 40 degrees dip to north is observed in eastern end of the aftershock zone.
Epicentral distribution and strike-slip mechanisms for the November 27, 2005 Qeshm earthquake reveals that the main shock with reverse mechanism activated the strike-slip basement faults. It implies that besides of reverse faults, basement strike-slip faults are involved in deformation of this part of Zagros.
Keywords:
Aftershocks, Fault, Qeshm, Seismotectonics, Zagros