Tectonic Deformation using Interferometry SAR
Saadatfar, Ehsan1; Dehghani, Maryam2; Esmaeily, Ali3
1Kerman Graduated University Technology, Department of remote sensing engineering, Kerman, Iran, IRAN, ISLAMIC REPUBLIC OF; 2Dept. of Civil and Environmental Engineering, School of Engineering, Shiraz University, IRAN, ISLAMIC REPUBLIC OF; 3Kerman Graduated University of Technology, Department of remote sensing engineering, Kerman, Iran, IRAN, ISLAMIC REPUBLIC OF
Study of earthquake faulting in Iran has shown that the early Quaternary tectonic history as well as the pre-Quaternary geological record is very important in understanding the present-day continental deformation during earthquakes.
In general seismicity is discontinuous and earthquakes show seismic gaps of several years to several centuries. The tectonic movements during the late Neogene-early Quaternary and the mechanism of the recent active fault motions show that the Iranian plateau is a ‘broad zone of compressional deformation'. The plateau is a relatively weak belt affected by several collisional orogenic movements and is being compressed between two blocks of greater rigidity (Arabia and Eurasia).We are going to measure the displacements occurred in faults and structures to study the tectonic activities. NW Iran is a region of intense deformation and seismicity situated between two thrust belts of the Caucasus to the north and the Zagros Mountains to the south which is the case study of the this project. In this project we will be tried to overcome the problems which conventional InSAR is encountered. The main problems are temprol decorrelation so that conventional interferometric synthetic aperture radar (InSAR) is a very effective technique for measuring crustal deformation, almost any interferogram includes large areas where the signals decorrelate and no measurement is possible and temporal decorrelation is occurred when the study area is mainly covered by vegetation.We use Persistent scatterer (PS) InSAR method to overcome the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms, and measuring small deformations that monitoring the phenomena with small deformation signals such as tectonic activities is a difficult task using conventional Interferometry because the deformation signal is mostly masked by atmosphere and residual topographic effects. Hence, in order to estimate the small deformation signals, PSI technique is the most proper method. We use Stanford Method for PSI (StaMPS) technique that uses spatial correlation of interferogram phase to find pixels with low-phase variance in monitoring the deformation caused by tectonic activities.
The method used to monitor a phenomenon is selected based on the nature of the phenomenon and the study area. Therefore, in order to cover a wide range of applications, different phenomena located in different parts of Iran are selected.
The data search stage consists of searching for appropriate data that will ensure adequate data quality and capable of yielding optimal result for the InSAR processing. We are trying to use all radar data available within each study area particularly while using PS Interferometry. The most suitable data that is mainly covering Iran is ENVISAT ASAR.
The main innovation of the project contains three main parts:
1.To avoid high geometrical decorrelation we use StaMPS which uses a co registration algorithm that applies amplitude based method to estimate offsets in position between pairs of images with good correlation. The density is significantly increased in the rural and mountain areas, which constitutes the main advantage of StaMPS.
2.conventional Interferometry has two main limitation: The first limit is related to temporal decorrelation which makes InSAR measurements unfeasible over such cultivated land and the second limit of InSAR is the spatial gradient or deformation time rate. Since these limitation of conventional interferometry, we use Persistent Scatterer (PS) technique that deals with these problems in an new way. The PS technique offers a systematic processing strategy,capable of utilizing all archived SAR data of a certain area from repeat orbits, and creating a stack of differential interferograms that have a common master image.
3. Most geodetic techniques such as GPS require repeated ground surveys in order to make measurements of surface deformation; also they are costly and time-consuming. InSAR is a relatively new tool that does not require ground surveys, and can make precise measurements of surface deformation across wide areas in most parts of the world.
The main objective of the project is measuring the displacements occurred in faults and structures to study the tectonic activities, measurements of the deformation can then be used in order to model or control the phenomena and slip rate of fault can be determined with PSI algorithms.
The results will contain extension of the deformation caused by tectonic activities, deformation time series of faults and interpretation of deformations.