Investigating continental deformation using PS InSAR

I use Persistant Scatterer Interferometric Synthetic Aperture Radar (PS InSAR) to measure interseismic strain accumulation across the Kunlun Fault, observe and model the postseismic signal associated with the Mw 7.8 2001 Kokoxili earthquake, and map strain in Western Turkey. PS InSAR selects pixels whose echo is dominated by a single scatterer in a series of interferograms (Hooper et al., 2004). To date most tectonic signals measured with InSAR have used Differential InSAR (DifSAR) rather than PS InSAR. I compare PS InSAR and DifSAR across the Kunlun Fault to obtain equivalent slip rates of 9.5 mm/yr and 10.5 mm/yr, respectively. I show that regions which are incoherent in DifSAR, are coherent using PS InSAR. Knowledge of slip rates along faults has important implication in terms of seismic hazard and is key to our understanding of the mechanical behaviour of the crust and mantle; for example they can be used to test the prediction of various models (Van Der Woerd et al., 2002). I show slip rate variability on the eastern Kunlun Fault in Tibet with rates reducing eastwards by upwards of 9 mm/yr over a region of upwards of 80 km to a slip rate of 2.4 mm/yr towards the fault tip. To date both afterslip and viscoelastic relaxation have been proposed as plausible mechanisms (Wen et al., 2012) for the Kokoxili earthquake. I model afterslip across the Kunlun Pass Fault using rate and state friction to create a series of models with various preseismic slip rates and frictional parameters. I then perform a parameter space search to find the best fitting models to ENVISAT data from 2003-2010. I compare the best fit afterslip model with viscoelastic relaxation to show that viscoelastic relaxation gives a better fit to the data. A number of studies have looked at interseismic strain accumulation across the North Anatolian and East Anatolian faults, e.g. Walters et al. (2014); Yamasaki et al. (2013), but relatively little work has been done on a fault scale across the grabens in Western Turkey. GPS data for the region shows fairly uniform strain (Aktug et al., 2009). I compare PS InSAR with GPS data to see whether the spatial resolution of the GPS is too low to resolve strain localisation. I then combine the two data sets to generate velocity and strain rate maps, which can be used for seismic hazard assessment, and to distinguish between different dynamic models of continental deformation.