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Summary of Proposal GEO2665

TitleSpatial and temporal variations of surfacedeformation in the Pamir - Tian Shan collision zone
Investigator Bookhagen, Bodo - Universität Potsdam, Institut für Erd- und Umweltwissenschaften
Team Member
Graduate Student Bufe, Aaron - UC Santa Barbara, Department of Earth Science
SummaryThe western end ofthe Tarim Basin, trapped between the Pamir and Tian Shan mountain ranges innorthwestern China, is one of the fastest deforming mountain ranges in theworld with shorteningrates of ~20mm/yr. Recent field surveys and dating work has established some constraints ofthe kilo-milion year timescale deformation of the major structures in theregion. Comparison with GPS data points to a general agreement between longterm and geodetic shortening rates. InSAR will allow us to obtain a highresolution map of spatial variations of surface deformation as well asilluminate the style and mode of deformation of faults and detachment folds inthe area. We aim to use InSAR in conjunction with longer-timescale records ofdeformation to 1) study the spatial variation of surface deformation in thisrapidly shortening region; 2) investigate the mode and style of deformation ofstructures in the area; and 3) compare rates and patterns of uplift across timescales.We are currently processing ENVISAT data for two frames spanning a 6 yearinterval. Preliminary results are promising but in order to better resolvedeformation on structures moving at rates < 1mm/y, a longer time series isrequired. Anticipated Resultsand Deliverables The proposed research will generate a time series ofInSAR-based deformation for the Kashgar region in NW China. This area istectonically active, but remote-sensing derived rates have not been calculatedfor this densely populated area. Preliminary studies based on ENVISAT confirmthe partly rapid deformation rates. Preliminary vertical surface velocities areon the order of 0.1-10 mm/yr. We have calculated interferograms using 90-m SRTM and 30-m ASTER topography. Because ofthe large uncertainty of the topography datasets and becase overall absoluteerror of <7 m (Farr et al., 2007) are most likely producing InSARrate-change errors on the order of <0.5 mm/yr, we will attempt to generate ahigh-resolution DEM generated from TerraSAR-X pairs or the high-resolutionTanDEM-X DEM to remove the topographic phase for this region. Additionalsources of InSAR uncertainties arise from differences in atmospheric watervapor between radar pairs (Hansen, 2001). In general, after the topographiccomponent is removed from the interferometric phase, the residual phase oftenincludes a signal that mimics the topography due to phase-propagation delaythrough the wet troposphere (Hansen, 2001). We have climatic data available forthis region that we will use in conjunction with numerical model outputs, butalso MODIS satellite data to correct for these effects. However, the analysisof the ENVISAT data indicates a low-to-moderate atmospheric moisture content. The deformation rates based on TerraSAR-X interferometry constitutean important boundary condition for numerical models describingmountain-building processes. The InSAR-derived rates on ~annual timescales willbe compared to decadal rates from ENVISAT and deformation rates onmillennial-timescales derived from the offset of dated geomorphic markers(fluvial terrace and deformed anticlines). This will generate a more coherentimage of tectonic deformation and natural hazards in the Kashgar region in NWChina. Justification of datarequested The team relies on archived data and requests additionaldata to be collected (if possible) with center point at 39.64N and 76.01E). Ourmain focus, however, is the analysis of existing data that have been archivedin the catalog. There exist data for this region until January 2014. We willfocus on data for the summer months to avoid issues with snow cover (data willbe used from May to Oct each year). Funding of the ResearchWork for the PI and Co-I The PI is a W3 professor at the University of Potsdam and haspreviously received funding from NASA, National Science Foundation (NSF), and theGerman Science Foundation (DFG).

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