Abstract
Determining and studying the crustal strain tensor allows describing geodynamic processes such as stress accumulation, which is an important parameter in seismic hazard assessment. In this study, the geodetic strain rate for the Western Alborz and Azerbaijan regions was calculated using geodetic data and the finite element method. The results of the geodetic strain calculation for the Khoy region show a right-lateral strike-slip shear in the NW-SE direction along with a compressional component. In the northern area of Tabriz, these results show a right-lateral strike-slip shear with a compressional component in the E-W direction in the area around the GhoshaDaghi fault. In the Western Alborz region, the results obtained from the calculation of geodetic strain for the eastern part of the range to the westernmost part of the Rudbar fault show a left-lateral strike-slip shear along the WNW-ESE direction with a tension perpendicular to the structure of the region. The magnitude and direction of the velocity vectors in the northern and southern parts of the western mountain range show a right-lateral strike-slip shear with a tension perpendicular to the mountain range.
Introduction

Calculating and examining geodetic strain as the current active deformation at the surface of the Earth's crust in a region and comparing it with seismic deformations or focal mechanisms of earthquakes occurring in the deep parts of that region as well as deformations in surrounding areas can be helpful both in better understanding active tectonics and in assessing the risk of future earthquakes.
This paper is dedicated to comparing tectonic deformations recorded by geodetic surveys in three separate regions of khoy, Varzaghan, and Rudbar in Iranian Azerbaijan and Western Alborz. Large strike-slip faults and rough mountains are common features of the study areas, and all three areas are directly affected by the northward movement of the Arabian plate and its interaction with the southern Caspian backstop (Solaymani Azad et al., 2019). Seismic hazard is one of the main problems of the study areas, as demonstrated by recent large earthquakes. Since Iran is currently covered by a GPS geodetic network, it is possible to calculate the geodetic strain rate tensor and compare it with seismic strain rate tensors or focal mechanisms of earthquakes that occurred in the region.

Research Method
In this study, the Delaunay triangulation method and geodetic velocity vectors were used to calculate the geodetic strain rate, and the planar velocity gradient tensor was calculated separately for each triangle. In order to calculate the geodetic strain rate tensor and estimate the kinematics of the study area, GPS data published in the article by Khorrami et al. (2019) were used. The velocity vectors used in this study are relative to the Eurasian frame.
The study area was divided into 12 triangular grids in the Rudbar region, 16 triangular grids in the Varzaghan region, and 14 triangular grids in the Khoy region. A GPS station is located at the vertex of each triangle.
Based on the hypothesis that the velocity field v varies linearly within each triangular subnetwork spanning the GPS network, we calculate the average horizontal velocity gradient L = grad(v) on each triangle. Since the velocity gradient generally incorporates both deformation and rotation, this two-dimensional tensor is asymmetric. L can be separated into a symmetric and an antisymmetric part as follows:

Its symmetric part is the strain-rate tensor while its antisymmetric part provides a local measure of the rigid rotation rate (Malvern 1969).

Discussion and Conclusion
To estimate the kinematics of the study area, GPS data published by (Khorrami et al., 2019) were used. The velocity vectors used in this study are relative to the Eurasian fixed frame.
The results obtained from the geodetic strain calculated for the Western Alborz region as well as the velocity vectors used show a left-handed shear in the WNW-ESE direction in the eastern part of the studied area. This left-handed shear is accompanied by a NNE-SSW stretch due to the divergence of the axes of minimum elongation (e2). In the west of the Western Alborz region, the direction of the velocity vectors obtained for the north of the mountain compared to its south shows a right-handed shear in the WNW-ESE direction. The amount of geodetic strain also decreases from east to west and the elongation axes show smaller values. These results are in good agreement with the effects of the interaction of the South Caspian basin on the Arabian-Eurasian convergence in the NNW area of Iran (Soleimani Azad et al., 2019).
Also, according to the results obtained from the calculation of geodetic strain and velocity vectors plotted in the northern region of the North Tabriz Fault, a dextral shear with an approximately east-west trend is visible in this area. Considering the location of the Ghosha-Daghi fault zone (which passes through the middle of this range), it can be related to the function of this fault. This dextral shear is accompanied by its pressure in the WNW-ESE direction, considering the convergence of the axes of minimum elongation (e2) obtained from the geodetic strain calculations. These results also have a good agreement with the tectonic transpression proposed by many researchers in the NW area of Iran (such as; Jackson, 2002; Soleimani-Azad et al., 2015). The geodetic velocity vectors plotted in the functional area of the Siyeh-Cheshme-Khoi fault and its surroundings show a clear dextral shear with a NW-SE trend for this range. This dextral shear is associated with a NNW-SSE orientation due to the convergence of the minimum elongation axes (e2). All velocity vectors obtained from GPS stations located in the northeast of the study area show a clockwise rotation relative to the stations in the southwest of the area, indicating dextral shear in this part of the study area. The Gilato-Siyeh-Cheshme-Khoi, Chaldran and Mako faults, which have a northwest-southeast trend, are located in this zone and each of them could be responsible for attenuating a part of this dextral shear.