G018-03
Interseismic Strain Accumulation On The Main Recent Fault (Iran) From Sentinel-1 Data

Tuesday, 15 December 2020: 07:08
Virtual
Andrew Watson, University of Leeds, COMET, School of Earth and Environment, Leeds, LS2, United Kingdom, John R Elliott, University of Leeds, COMET, School of Earth and Environment, Leeds, United Kingdom, Richard J Walters, COMET, Durham University, Department of Earth Sciences, Durham, United Kingdom, Gregory A Houseman, University of Sydney, School of Geosciences, Sydney, Australia and Douglas Paton, University of Leeds, School of Earth and Environment, Leeds, United Kingdom
Recorded Presentation
Abstract:
The Main Recent Fault (MRF) is a major right-lateral transform fault in the Zagros mountains of Iran. An accurate estimate of the rate of interseismic strain accumulation is critical both for estimating local seismic hazard, and for developing understanding of the overall distribution and mechanics of continental deformation across Iran. However, there has been major disagreement between previous estimates of the rate of slip on this important fault: previous estimates from regional GNSS observations and geological offsets vary between 1.6-17 mm/yr. Whilst the fault is favourably orientated for measurement with InSAR, no previous InSAR velocity estimates have been published to-date.

Here we use Sentinel-1 observations to make the first InSAR estimate of the interseismic slip velocity and locking depth for a ~400 km section of the MRF. We use the LiCSAR automated system to process 5.5 years of Sentinel-1 SAR acquisitions for four adjacent and overlapping frames (two ascending and two descending), producing a total of ~2500 interferograms. We apply a NSBAS-type approach using LiCSBAS in order to derive satellite line-of-sight velocities, mitigating the effects of atmospheric noise using GACOS. We estimate north-south velocities from regional GNSS and use this to isolate the fault-parallel and vertical velocity components from the overlapping ascending and descending InSAR frames. Finally, in order to estimate the slip-rate and locking depth for the MRF, we fit an approximate 2-D screw dislocation to the velocity field using an elastic half-space model and a Bayesian approach.

Our preliminary results show an interseismic slip velocity of 1-6 mm/yr below a locking depth of 10 km. The locking depth is relatively poorly constrained because of the presence of incoherence and large subsidence signals close to the fault trace, and because the slip rate is close to the current sensing limit of Sentinel-1 time series (2-3 mm/yr). These results show that the MRF is an important major crustal structure that shows clear localisation of strain at depth and which accommodates a significant portion of the relative motion between Arabia and Eurasia. However, the overall slip rate is towards the lower end of the range of previous estimates, supporting previous GNSS-derived rates but which is inconsistent with longer-term estimates.

<< Previous Abstract | Next Abstract >>