Observation of Surface Creep from InSAR and other geodetic data
Yu-Jen Chang
Abstract
Geophysical applications of radar interferometry to measure changes in the Earth’s surface have exploded in the early 1990s. This new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times. The resulting interferogram is a contour map of the change in distance between the ground and the radar instrument. Application of Radar Interferometry can efficiently observe the land surface deformation. There are two successful studies using the SAR Interferometry to observe surface creep. The first case is the San Andreas fault in the west of United States, and the other is the LongitudinalValley fault in eastern Taiwan. The San Juan Bautista (SJB) segment forms the northern transition zone of the creeping section of the San Andreas fault. It is an area of moderate seismicity; the largest instrumentally-recorded earthquakes have been M5.5. However, historic records suggest six M ≧6 earthquakes occurred near the SJB segment between 1840 and 1899. It is also an area that has experienced several slow earthquakes. I. A. Johanson perform a joint inversion of GPS and InSAR (Interferometric Synthetic Aperture Radar) data to determine the current rate and distribution of interseismic creep. On the other hand, Leslie Hsu use InSAR analysis in eastern Taiwan to study reverse creep on the LongitudinalValley fault (LVF). The InSAR results support the view that although surface creep is rapid in certain locations, significant portions of the LVF are locked and thus represent a substantial seismic hazard.
Reference
I. A. Johanson and R. Burgmann 2005, Creep and quakes on the northern transition zone of the San Andreas fault from GPS and InSAR data, Geophysical Research Letters, vol. 32, l14306.
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Leslie Hsu and Roland Burgmann 2006, Surface creep along the LongitudinalValley fault, Taiwan from InSAR measurements, Geophysical Research Letters, vol. 33, l06312.
Massonnet, D., and K. Feigl 1998, Radar interferometry and its application to changes in the Earth’s surface, Rev. Geophys., 36(4), 441– 500.
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