Radar Determination of Fault Slip and Location in Partially Decorrelated Images
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Faced with the challenge of thousands of frames of radar interferometric images, automated feature extraction promises to spur data understanding and highlight geophysically active land regions for further study. We have developed techniques for automatically determining surface fault slip and location using deformation images from the NASA Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR), which is similar to satellite-based SAR but has more mission flexibility and higher resolution (pixels are approximately 7 m). This radar interferometry provides a highly sensitive method, clearly indicating faults slipping at levels of 10 mm or less. But interferometric images are subject to decorrelation between revisit times, creating spots of bad data in the image. Our method begins with freely available data products from the UAVSAR mission, chiefly unwrapped interferograms, coherence images, and flight metadata. The computer vision techniques we use assume no data gaps or holes; so a preliminary step detects and removes spots of bad data and fills these holes by interpolation and blurring. Detected and partially validated surface fractures from earthquake main shocks, aftershocks, and aseismic-induced slip are shown for faults in California, including El Mayor-Cucapah (M7.2, 2010), the Ocotillo aftershock (M5.7, 2010), and South Napa (M6.0, 2014). Aseismic slip is detected on the San Andreas Fault from the El Mayor-Cucapah earthquake, in regions of highly patterned partial decorrelation. Validation is performed by comparing slip estimates from two interferograms with published ground truth measurements.
KeywordsRadar interferometry fault slip computer vision Canny algorithm
This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology under contract with NASA. The work was funded by NASA Earth and Space Science program, NASA’s EarthScope Geodetic Imaging UAVSAR program, Advanced Information Systems Technology (AIST) program for QuakeSim work, and the ACCESS program for GeoGateway development. We thank the UAVSAR team and in particular Yunling Lou, Brian Hawkins, Naiara Pinto, and Yang Zheng for collection and processing of the UAVSAR data.
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