Seismicity, Velocity Structure and Tectonics of the Arabian Plate

Volume 1 , Issue 1 , January 2016 , Pages 481-497

Authors

¹ Array Information Technology, 5130 Commercial Drive, Suite B, Melbourne, FL 32940, USA

² Washington University in Saint Louis, Campus Box 1169, One Brookings Drive, Saint Louis, MO 63130, USA

The deployment of the North Iraq Seismographic Network (NISN) and of the array

KSIRS and the implementation of the virtual Middle East Seismographic Network

(vMESN) produced a wealth of unprecedented data for use in studying the seismicity,

velocity structure and some aspects of the tectonic activities associated with the Arabian

plate dynamics. Recent studies using stationary Global Positioning System (GPS)

stations in the region clearly show the northeast trending transitional and

counterclockwise rotational motions of the plate. Most of the seismicity is occurring in

the crust along the Zagros and Taurus mountain ranges and their foothills, along the

Dead Sea transform fault and along the rift zones in the Red Sea and the Gulf of Aden.

Earthquakes with magnitude greater than 5 mb are not frequent. Likewise, intermediate

and deep earthquakes are uncommon in the region. The great majority of the

earthquakes occur as a result of the continental collision between the Arabian plate and

the Iranian and Turkish plateaus. Preliminary analysis of the earthquakes’ spatial

distribution suggests likely alignment with the faults in the region. Moment tensor

analysis of the larger events, carried out as part of the routine data processing, suggests

their focal mechanisms vary from normal, reverse to strike-slip depending on the local

stress pattern and the event’s location relative to the Zagros and Taurus suture zones.

The three-dimensional crustal seismic velocity structure of the Arabian plate and

surrounding regions estimated from the dispersion of Rayleigh surface waves reflects the

impact of the overlying 5-10 km thick sedimentary column on the morphology of the

crystalline basement, the Conrad and Moho discontinuities whose depths range from 20-

25 km and 40-50 km, respectively. The teleseismic P-wave receiver function analysis

provided an independent verification of the velocity models beneath the various stations

used in the study of the region. In summary, the resulting models show remarkable

correlation between the distribution of shear velocities and the major physiographic and

tectonic provinces of the Arabian plate, Turkish and Iranian plateaus. It also helped

delineate the extent of the Red Sea rift and the roots of the Zagros and Taurus mountain

ranges.

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