Seismic and magnetotelluric interpretation near Parkfield, California: Testing 
a joint inversion of independet data sets

Julia, J.; Shalev, E.; Chavarria, J.; Onacha, S.; Malin, P. E.; Hole, J. A.; Ryberg, Trond; Cumming, W. B.; Suemnicht, G.

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Seismic and magnetotelluric interpretation near Parkfield, California: Testing a joint inversion of independet data sets

Authors

Julia, J.
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Shalev, E.
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Chavarria, J.
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Onacha, S.
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Malin, P. E.
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Hole, J. A.
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Ryberg, Trond
2.2 Geophysical Deep Sounding, 2.0 Physics of the Earth, Departments, GFZ Publication Database, Deutsches GeoForschungsZentrum;

Cumming, W. B.
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Suemnicht, G.
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Citation

Julia, J., Shalev, E., Chavarria, J., Onacha, S., Malin, P. E., Hole, J. A., Ryberg, T., Cumming, W. B., Suemnicht, G. (2004): Seismic and magnetotelluric interpretation near Parkfield, California: Testing a joint inversion of independet data sets, (EOS, Transactions, American Geophysical Union, Suppl.; Vol. 85, 47), AGU 2004 Fall Meeting (San Francisco 2004) (San Francisco).

https://gfzpublic.gfz-potsdam.de/pubman/item/item_232672

Abstract

We present a simultaneous interpretation of coincident magnetotelluric (MT) and seismic refraction lines near the Parkfield, CA, San Andreas Fault Observatory at Depth site. The MT data set was acquired with Phoenix 4-channel systems with average station spacing of about 250 m over a profile length of ($sim$5000) m. The time-domain recording scheme was designed to yield data in the 0.01-200 Hz frequency band. The seismic travel-times were obtained from a SAFOD-related refraction/reflection line that was shot in the fall of 2003. The station and shot spacing for the line section coincident with the MT data were 50~m and 500~m, respectively. An initial, first-pass model of the seismic data suggests a simple structure lies beneath the study site: a 1.0-1.5 km thick, gradational, sedimentary layer with surface topography over a more uniform igneous basement. Modeling of the MT data alone shows a significant trade off exists in these data between the sediment thickness and the basement resistivity. To integrate the separate seismic and MT interpretations we combine both data sets into a joint inversion scheme by assuming that rapid velocity changes are accompanied with correspondingly rapid resistivity changes. We expect the combination will yield a mutually consistent estimate of sediment thickness and basement topography beneath the studied line.