Estimating subtle long-wavelength deformation with InSAR: Application to the Chaman Fault
Abstract
While it's difficult to discriminate the tectonic deformation from the effects of orbital error in the single interferogram due to their similar spatial pattern, but their different temporal behavior is an opportunity to measure the tectonic deformation from the InSAR time-series. Considering the fact that the long-wavelength tectonic signal is correlated in time (in most cases linearly) whereas orbital errors have random distribution, theoretically we should be able to extract tectonic deformation signal from the InSAR time-series results. However in practice, systematic errors from various sources, usually misinterpreted as the orbital error, are the main obstacles to use current SAR archives for estimating long-wavelength deformation. In this presentation we will introduce a temporal systematic error in Envisat-ASAR data limiting our ability in using these data for estimating long-wavelength deformation and propose a processing strategy to correct it's effects in the time-series results. We will show using simulated data that the linear velocity map calculated from the InSAR time-series is not affected by the random orbital error. However in practice the velocity map of InSAR time-series from Envisat ASAR data is always affected by an approximately 1.5 cm/yr ramp in the range direction. This constant ramp in the results from Envisat should not be misinterpreted as the random orbital error but it's a result of systematic temporal error with possible sources from the radar hardware, processing parameters or softwares. Being aware of this systematic effect in the Envisat data enables us to propose a new processing strategy to correct the error without removing the long-wavelength deformation. We have examined this strategy to estimate the velocity map over Southern San Andreas Fault. These results show that the obtained velocity map using only Envisat InSAR data is very well comparable with other recent studies attempting to use GPS to correct the InSAR orbital error. Results from this study are very promising for InSAR community to explore the Envisat archive to measure long-wavelength deformation using the proposed strategy. We have applied the proposed processing strategy on the Envisat ASAR time-series data to measure the geodetic slip rate along the northern Chaman Fault. The preliminary results show the shallow fault creep along some segments of the fault, north of Chaman city. Velocity map from InSAR combined with seismic information in this area suggests strain partitioning between various known and unknown faults at the western Indian boundary.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.G51B1094F
- Keywords:
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- 1209 GEODESY AND GRAVITY / Tectonic deformation