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Shear wave anisotropy from cross-correlation of seismic noise in the Parkfield pilot hole
Article first published online: 12 DEC 2011
© 2011 The Authors Geophysical Journal International © 2011 RAS
Geophysical Journal International
Volume 188, Issue 2, pages 626–630, February 2012
How to Cite
Lewis, M. A. and Gerstoft, P. (2012), Shear wave anisotropy from cross-correlation of seismic noise in the Parkfield pilot hole. Geophysical Journal International, 188: 626–630. doi: 10.1111/j.1365-246X.2011.05285.x
- Issue published online: 5 JAN 2012
- Article first published online: 12 DEC 2011
- Accepted 2011 October 31. Received 2011 October 30; in original form 2011 August 28
- Body waves;
- Seismic anisotropy
We use cross-correlation of seismic noise recorded at stations in the San Andreas Fault Observatory at Depth (SAFOD) pilot hole to extract P and S waves and measure S-wave anisotropy on the horizontal components. The data are recorded at seven three-component stations at depths from 1857 to 2097 m in the pilot hole. In late September and early 2004 October drilling noise underneath the stations generated propagating waves, which were absent in the rest of October. Estimates of the P- and S-wave velocities from the cross-correlations, on the vertical and horizontal components, respectively, are consistent with velocity measurements taken directly in the borehole. We observe polarization of the S wave, with a fast polarization direction of 120°–130° that is 4 per cent faster than the slow direction. Cross-correlation of the seismic noise can accurately determine S-wave anisotropy.