[1] We present here a new InSAR persistent scatterer (PS) method for analyzing episodic crustal deformation in non-urban environments, with application to volcanic settings. Our method for identifying PS pixels in a series of interferograms is based primarily on phase characteristics and finds low-amplitude pixels with phase stability that are not identified by the existing amplitude-based algorithm. Our method also uses the spatial correlation of the phases rather than a well-defined phase history so that we can observe temporally-variable processes, e.g., volcanic deformation. The algorithm involves removing the residual topographic component of flattened interferogram phase for each PS, then unwrapping the PS phases both spatially and temporally. Our method finds scatterers with stable phase characteristics independent of amplitudes associated with man-made objects, and is applicable to areas where conventional InSAR fails due to complete decorrelation of the majority of scatterers, yet a few stable scatterers are present.

We present a modification to the adaptive Goldstein radar interferogram filter which improves the quality of interferometry products. The proposed approach makes the Goldstein filter parameter alpha dependent on coherence, such that incoherent areas are filtered more than coherent areas. This modification minimizes loss of signal while still reducing the level of noise.Index Terms-Phase filtering, phase statistics, radar interferometry, synthetic aperture radar (SAR).

Abstract-In the permanent scatterer technique of synthetic aperture radar interferometry, there is a need for an efficient and reliable nonlinear parameter inversion algorithm that includes estimation of the phase cycle ambiguities. Present techniques make use of a direct search of the solution space, treating the observations as deterministic and equally weighted, and which do not yield an exact solution. Moreover, they do not describe the quality of the estimated parameters. Here, we use the integer least squares estimator, which has the highest probability of correct integer estimation for problems with a multivariate normal distribution. With this estimator, the propagated variance-covariance matrix of the estimated parameters can be obtained. We have adapted the LAMBDA method, part of an integer least squares estimator developed for the ambiguity resolution of carrier phase observations in global positioning systems, to the problem of permanent scatterers. Key elements of the proposed method are the introduction of pseudo-observations to regularize the system of equations, decorrelation of the ambiguities for an efficient estimation, and the combination of a bootstrap estimator with an integer least squares search to obtain the final integer estimates. The performance of the proposed algorithm is demonstrated using simulated and real data.Index Terms-Nonlinear parameter inversion, permanent scatterers, synthetic aperture radar (SAR) interferometry.

We use a combination of Persistent Scatterer Interferometry (PSI) and GPS observations to study interseismic crustal deformation on the Gazikoy-Saros segment (Ganos fault) of the North Anatolian Fault (NAF) zone, northwestern Turkey. The data include 44 C-band radar images collected by the ERS1 and ERS2 satellites in descending orbits between 1992 and 2003 over the study area, and campaign GPS horizontal velocities from 7 stations. The resultant secular velocity field is inverted using a nonlinear minimization algorithm to estimate parameters of two interseismic deformation models: aseismic deep slip in a purely elastic earth model (elastic half-space rheology), and viscoelastic flow in an elastic-viscoelastic earth model (viscoelastic-coupling rheology). The following conclusions are drawn: (1) The fault locking depth is estimated in the range of ∼ 8-17 km (95% confidence interval) regardless of the rheological model. (2) The elastic half-space model implies an upper bound of 20-27 mm/yr for the slip rate on the Ganos fault. (3) Models incorporating viscoelastic rheology and seismic cycle effects suggest a lower slip rate of 18-24 mm/yr, which agrees more closely with geological estimates. However, these values are slightly sensitive to the assumed earthquake recurrence interval. (4) A bootstrap analysis of deformation data yields average crust-upper mantle viscosities of 1.3 × 10 19 -3.6 × 10 20 Pa s for the Ganos area.

This paper addresses the question of how to robustly estimate linear deformation at a large number of points from differential phase in an interferometric stack. The so-called "Permanent Scatterers technique" [1], uses a relatively large number of differential interferograms of the same area, coregistered at the same master SLC image. Linear deformation rates and DEM errors are estimated for pixels that have limited temporal decorrelation. This straightforward and generic setup has been used in a network approach that uses connections between nearby points to compute a velocity field for large areas.