[1] We present a new method to extract along-track displacements from InSAR data, based on split-beam InSAR processing, to create forward-and backwardlooking interferograms. The phase difference between the two modified interferograms provides the along-track displacement component. Thus, from each conventional InSAR pair we extract two components of the displacement vector: one along the line of sight, the other in the alongtrack direction. We analyze the precision of the new method by comparing our solution to GPS and offset-derived alongtrack displacements in interferograms of the 1999, Hector Mine earthquake. The RMS error between GPS displacements and our results ranges from 5 to 8.8cm. Our method is consistent with along-track displacements derived by pixel-offsets, which are limited to 12-15cm precision. The theoretical precision of the new method depends on SNR and coherence. For a signal to noise ratio of 30 the expected precisions are 3, 11cm for coherence of 0.8, 0.4, respectively. Citation: Bechor, N. B. D., and H. A.Zebker (2006), Measuring two-dimensional movements using a single InSAR pair, Geophys. Res. Lett., 33, L16311,

A network of 11 continuous GPS stations was constructed in Israel between 1996 and 2001 to monitor current crustal movements across the Dead Sea Fault (DSF). Analysis of the GPS measurements with respect to the ITRF2000 Reference Frame yields time series of daily site positions containing both secular and seasonal variations. Horizontal secular variations (station velocities) are evaluated with respect to the main tectonic element in the region, the DSF. We use six velocity vectors west of the DSF to define the ITRF2000 pole of the Sinai sub‐plate, and rotate the velocity field for all stations into the Sinai reference frame (SRF). The velocity vectors reveal that (1) relative station movements are less than 4 mm/yr; (2) the nine stations located west of the DSF show no statistically significant motion with respect to the SRF; and (3) the two stations located in the Golan Heights (KATZ and ELRO) and a station in Damascus, Syria (UDMC) show 1.7–2.8 mm/yr northward motion with respect to Sinai, indicating a left‐lateral motion along the DSF. Using locked‐fault models, we estimate the current slip rate across the DSF as 3.3 ± 0.4 mm/yr. If we exclude the northern sites (ELRO and UDMC), which are located adjacent to the compressional jog of Mount Hermon, our estimate increases to 3.7 ± 0.4 mm/yr. The calculated ITRF2000 Sinai, Eurasia, and Nubia poles and a published pole for Arabia allow us to calculate the current relative plate motion of Sinai‐Arabia and Sinai‐Nubia.

Postseismic displacements of as much as 14 cm were recorded by GPS measurements in the 3 months following the MW 7.6 1999 Chi‐Chi, Taiwan earthquake. Data from 35 continuous and 90 campaign‐surveyed stations, which show continued east over west thrusting, are analyzed to estimate the postseismic slip distribution and fault geometry. Assuming the shallow fault dips 24° E, as determined by numerous studies of the mainshock, we invert for the deeper fault structure. Our results show that the fault dip shallows with depth below the hypocenter, merging into a nearly horizontal decollement at a depth of 8–12 km. The afterslip distribution shows a maximum slip of 25 cm in the hypocentral region at 7–12 km depth as well as significant slip on the lower decollement. Afterslip is notably absent in the region of maximum coseismic slip, consistent with the afterslip being driven by the mainshock stress change.

The Dead Sea Fault (DSF) is a transform plate boundary between the Arabian plate and the Sinai sub‐plate. The rate of displacement across the fault has been estimated as 1–10 mm/yr. In this study we present a new estimate of the current displacement across the DSF, which is based on three years of continuous Global Positioning System measurements (July 1996 to July 1999). Our analysis of these data shows that relative northward velocity, which is the fault parallel component, on the baseline between Tel Aviv and Katzerin (Golan Heights) and Katzerin and Elat is 1.4 ± 0.3 mm/yr and −1.0 ± 0.5 mm/yr, respectively, assuming a colored noise (white noise plus flicker noise) model for the daily position estimates. By using a simple locked fault model, we estimate that during the three‐year observation period the relative plate motion across the DSF was 2.6 ± 1.1 mm/yr.

Ice velocity is one of the products associated with the Ice Sheets Essential Climate Variable. This paper describes the intercomparison and validation of ice-velocity measurements carried out by several international research groups within the European Space Agency Greenland Ice Sheet Climate Change Initiative project, based on space-borne Synthetic Aperture Radar (SAR) data. The goal of this activity was to survey the best SAR-based measurement and error characterization approaches currently in practice. To this end, four experiments were carried out, related to different processing techniques and scenarios, namely differential SAR interferometry, multi aperture SAR interferometry and offset-tracking of incoherent as well as of partially-coherent data. For each task, participants were provided with common datasets covering areas located on the Greenland ice-sheet margin and asked to provide mean velocity maps, quality characterization and a description of processing algorithms and parameters. The results were then intercompared and validated against GPS data, revealing in several cases significant differences in terms of coverage and accuracy. The algorithmic steps and parameters influencing the coverage, accuracy and spatial resolution of the measurements are discussed in detail for each technique, as well as the consistency between quality parameters and