Applications of attenuation tomography to Imperial Valley and Coso-Indian Wells Region, southern California
Abstract
Spatial variations in seismic wave attenuation were tomographically imaged from observed S to P wave amplitude ratios in the Imperial Valley and Coso-Indian Wells regions of southern California. In the Coso-Indian Wells region a highly attenuating body (S wave quality factor Q_β ≈ 30) coincides with a slow P wave anomaly mapped by Walck and Clayton (1987). This coincidence suggests the presence of a 3- to 5-km depth magmatic or hydrothermal body in the Indian Wells region. In the Imperial Valley, slow P wave travel time anomalies and highly attenuating S wave anomalies were found in the Brawley seismic zone at a depth of 8–12 km. The effective S wave quality factor is very low (Q_β ≈ 20), and the P wave velocity is 10% slower than the surrounding areas. These results suggest either magmatic or hydrothermal intrusions, or fractures at depth, possibly related to active shear in the Brawley seismic zone. This attenuation tomographic technique is shown to be useful in delineating the spatial variations in seismic wave attenuation and in estimating the effective seismic quality factor of attenuation anomalies.
Additional Information
© 1988 American Geophysical Union. Received 18 March 1987; accepted 6 March 1988. We thank Chris Sanders for valuable suggestions in the early stage of this study and providing us with the Coso data set and Marianne Walck for providing us with the results obtained in the Coso-Indian Wells study (Figure 7). We also thank Christof Stork for supplying the three-dimensional ray-tracing code. Discussions with Art Frankel, Carl Johnson, Kerry Sieh, Richard Stead, and John Vidale have been very helpful. We also thank Luciana Astiz, E. Kissling, Harold Magistrale, William Menke, Richard Stead, John Vidale, and two anonymous reviewers for reviewing the manuscript. This work is supported by USGS grant 14-08-0001-G1171 and in part by a grant from the Keck Foundation. Contribution no. 4437, from the Division of Geological and Planetary Sciences, California Institute of Technology.Attached Files
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Additional details
- Eprint ID
- 34917
- Resolver ID
- CaltechAUTHORS:20121016-103928185
- 14-08-0001-G1171
- USGS
- W. M. Keck Foundation
- Created
-
2012-10-17Created from EPrint's datestamp field
- Updated
-
2021-11-09Created from EPrint's last_modified field
- Caltech groups
- Seismological Laboratory, Division of Geological and Planetary Sciences
- Other Numbering System Name
- Caltech Division of Geological and Planetary Sciences
- Other Numbering System Identifier
- 4437