Estimating Slip Distribution by the Combination of
InSAR and GPS Measurements

Presenter: Ting-Yu Liu              Adviser: Wu-Lung Chang, Chung-Pai Chang

Abstract
The common geodetic data we often use are Global Position System (GPS) observation and satellite radar data which include both ascending and descending orbits of interferometric synthetic aperture radar (InSAR).  In order to obtain the variable slip distribution on the fault segments from GPS and satellite data, we use a nonnegative least-square method that includes an appropriate degree of smoothing to invert.  For the case of 16 October 1999 Mw 7.1 Hector Mine, California, Earthquake, Jonsson et al., first estimate variable dip of each fault segment, as well as the single constant right-lateral strike-slip component across each segment.  Then, the author fix the optimal fault segment dip (83∘) and discretize the fault segment into patches of 1.5 x 1.5 km, and calculate the variable slip distribution.  The data include campaign GPS observations from 55 stations and both ascending and descending orbits InSAR displacement deformation.  Another fault slip distribution solution estimated from geodesy data by Simons et al., using different ways to reduce the number of data and smoothing.  The distribution of slip that we wish to find includes strike-slip and dip-slip component obtain by joint inversion, while the fault patches were not discretized into the same size across the whole fault plane, but increase with the depth.  
The total geodetic moment are 5.93 x 1019 Nm (Mw7.1) and 6.7 x 1019 Nm from S. Jónsson et al., 2002 and M. Simons et al., 2002, respectively. The results are similar to previous seismic moment estimates of 4~6 x 1019 Nm. 

References
Jónsson, S., H. Zebker, P. Segall, and F. Amelung (2002). Fault Slip Distribution of the 1999 Mw 7.1 Hector Mine, California, Earthquake, Estimated from Satellite Radar and GPS Measurements, Bull. Seism. Soc. Am. 92, 1377-1389.

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Simons, M., Y. Fialko., and L. Rivera (2002). Coseismic Deformation from the 1999 Mw 7.1 Hector Mine, California, Earthquake as Inferred from InSAR and GPS Observations, Bull. Seism. Soc. Am. 92, 1390-1402.

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Welstead, S. T. (1999). Fractal and Wavelet Image Compression Techniques, SPIE Optical Engineering Press, Bellingham, Washington, 232 pp.

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