Measurement of Along-track Displacements due to the M6.0 August 24, 2014 South Napa Earthquake Using X-band Multiple-Aperture SAR Interferometry
Min-jeong Jo1, Sang-Ho Yun2, Hyung-Sup Jung3, Hae-Ik Jung4, Young-Chang Koh4 and Frank Webb5, (1)Yonsei University, Seoul, Korea, Republic of (South), (2)Jet Propulsion Laboratory, Pasadena, CA, United States, (3)University of Seoul, Seoul, Korea, Republic of (South), (4)National Geographic Information Institute, Suwon, Korea, Republic of (South), (5)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, United States
Abstract:
Multiple-aperture SAR interferometry (MAI) has been developed for measuring surface displacements in along-track direction as an alternative method of amplitude offset tracking method. Various studies on geological phenomena have been carried out using MAI technique with C-band and L-band SAR data, but application of MAI to X-band SAR is challenging due to its more severe temporal decorrelation compared to longer wavelength radar. The Italian Space Agency’s (ASI) COSMO-SkyMed (CSK) mission consisting of four identical radar satellites has a powerful capability to minimize temporal baselines maintaining high coherence. This offers a good chance for MAI application for precise measurement of along-track displacements. In this study, we demonstrate the MAI performance of X-band SAR for the M6.0, South Napa Earthquake occurred on August 24, 2014. A coseismic CSK pair data (July 26 and August 27, 2014) acquired from descending orbit was used to show the along-track displacements in the fault zone.
In order to evaluate the precision for measuring MAI deformation on the Napa Earthquake using CSK data, we produced a coherence map of the interferogram because the MAI precision is a function of interferometric coherence. However, we found that standard deviation of MAI phase does not coincide with the theoretical variation. The measurement uncertainty of along-track displacements was estimated by using the predefined empirical equation which was established through the performance test using multi-path CSK dataset at Kilauea Volcano region. The uncertainty map of the along-track displacements in the South Napa Earthquake region provides a reliable metric to estimate the variance/covariance of the data, useful for 3-D displacement field construction and geophysical modeling.
