Document Type : Research Paper
Authors
Abstract
A new and significant source of information on earthquake studies has been provided by space geodesy. The data which are gathered by various techniques of space geodesy, can quantify potential of seismic activity in the region of interest. To achieve this goal, the main advantage of extra-terrestrial geodetic data in comparison with the conventional data from geology and seismology is the ability of this data in portraying the present kinematics of the area with faults that are unknown, too slowly slipping, or too deeply buried. Seismic moment rate, that can be calculated based on geological fault data and historical earthquake catalogue, is the amount of accumulation of earthquake potential in a region. Space geodetic data are used in the deformation analysis for quantifying strain rate tensor. The strain tensor is related to the moment rate tensor according to Kostrov formula presented in 1974 for the first time. In 1994, Ward calculated geodetic seismic moment rate by means of eigenvalues of strain rate tensor. The seismic moment rate that are calculated based on these three discipline, namely geodesy, geology and seismology can grant us a comprehensive view of seismic potential of the region. Since 1999 the National Cartographic Center (NCC) of Iran has been established and maintained a high precision geodetic network in the region of Iran. The network has 28 stations on two of the main plates, namely Eurasian and Arabian plates. This is a long term project, with planned re-observations every two years. First epoch of GPS measurements was done in 1999 and the second GPS campaign was carried out in 2001.
This paper will focus on this data to derive geodetic seismic moment rates. Our results show that south-east region and central
Alborz presents largest values of the seismic moment rates in comparison to other parts
of Iran. The moment rates in area unit are 5.7659x1015(N m-1 yr-1) and 2.0147x1015
(Nm-1 yr-1) over the predefined seismic regions of south-east and central Alborz, respectively. The derived magnitudes of the seismic moment rate show the smallest value in north-east region. The determined rate is equal to 1.0832x1015(N m-1 yr-1) in this region.
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