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Northridge Earthquake GPS Results:

The static displacement field of the earthquake was precisely measured at 66 stations using GPS. These measurements were then modeled by computer to produce an image of the slip on the fault plane that ruptured in the earthquake, as shown below.

In July 1996, a paper containing the GPS data set and models of the earthquake source was published in the BSSA special issue on the Northridge earthquake. An electronic version of the reprint of this paper is available on-line. This electronic version contains tabulated data that can be saved as text files. Hard copies of the reprint are available by request.

This diagram shows the topography of the Northridge area, based on the USGS DEM, and graphics generated by GMT. The projection is such that the fault slip model is shown head-on, undistorted.

The GPS data were inverted using SVD techniques implemented in Shawn Larsen's GINV code. There are 5 x 6 subfaults, each 4 km square, and we inverted for thrust and strike slip on each subfault (rake vectors for each subfault are shown in blue).

A more recent version of the modeling results is contained in the paper (but has not been incorporated into the image above).

References

Hudnut, K., Z. Shen, M. Murray, S. McClusky, R. King, T. Herring, B. Hager, Y. Feng, P. Fang, A. Donnellan, and Y. Bock, Co-seismic displacements of the 1994 Northridge, California, earthquake, Bulletin of the Seismological Society of America (Special Issue on the Northridge Earthquake). electronic reprint available

Hudnut, K. W. et al., Co-seismic displacements of the 1994 Northridge, California, earthquake Fall 1994 AGU Meeting abstract: EOS v. 75, No. 44, pg. 176; G32B-09

For more information, contact Ken Hudnut at hudnut@gps.caltech.edu

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