| Abstract: | Integrated vibroseis compressional and experimental hammer-source, shear-wave, seismic reflection profiles across the Provo segment of the Wasatch fault zone in Utah reveal near-surface and shallow bedrock structures caused by geologically recent deformation. Combining information from the seismic surveys, geologic mapping, terrain analysis, and previous seismic first-arrival modeling provides a well-constrained cross section of the upper ~500 m of the subsurface. Faults are mapped from the surface, through shallow, poorly consolidated deltaic sediments, and cutting through a rigid bedrock surface. The new seismic data are used to test hypotheses on changing fault orientation with depth, the number of subsidiary faults within the fault zone and the width of the fault zone, and the utility of integrating separate elastic methods to provide information on a complex structural zone. Although previous surface mapping has indicated only a few faults, the seismic section shows a wider and more complex deformation zone with both synthetic and antithetic normal faults. Our study demonstrates the usefulness of a combined shallow and deeper penetrating geophysical survey, integrated with detailed geologic mapping to constrain subsurface fault structure. Due to the complexity of the fault zone, accurate seismic velocity information is essential and was obtained from a first-break tomography model. The new constraints on fault geometry can be used to refine estimates of vertical versus lateral tectonic movements and to improve seismic hazard assessment along the Wasatch fault through an urban area. We suggest that earthquake-hazard assessments made without seismic reflection imaging may be biased by the previous mapping of too few faults. ?? 2010 Geological Society of America. |
| Genre: | Article |
| ProdID: | 70037704 |
| Citation Author: | McBride, J. H.; Stephenson, W. J.; Williams, R. A.; Odum, J. K.; Worley, D. M.; South, J. V.; Brinkerhoff, A. R.; Keach, R. W.; Okojie-Ayoro, A. O. |
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| Citation End Page: | 1814 |
| Citation Issue: | 11-12 |
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| Citation Language: | English |
| Citation Larger Work Title: | Bulletin of the Geological Society of America |
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| Citation Number Of Pages: | 15 |
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| Citation Search Results Text: | Shallow subsurface structure of the Wasatch fault, Provo segment, Utah, from integrated compressional and shear-wave seismic reflection profiles with implications for fault structure and development; 2010; Article; Journal; Bulletin of the Geological Society of America; McBride, J. H.; Stephenson, W. J.; Williams, R. A.; Odum, J. K.; Worley, D. M.; South, J. V.; Brinkerhoff, A. R.; Keach, R. W.; Okojie-Ayoro, A. O. |
| Citation Start Page: | 1800 |
| Citation Volume: | 122 |
| Citation Year: | 2010 |
| Type: | citation/reference |
| Text: | Shallow subsurface structure of the Wasatch fault, Provo segment, Utah, from integrated compressional and shear-wave seismic reflection profiles with implications for fault structure and development; 2010; Article; Journal; Bulletin of the Geological Society of America; McBride, J. H.; Stephenson, W. J.; Williams, R. A.; Odum, J. K.; Worley, D. M.; South, J. V.; Brinkerhoff, A. R.; Keach, R. W.; Okojie-Ayoro, A. O. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/outside_thumb.jpg |
| URL (DIGITAL OBJECT IDENTIFIER): | http://dx.doi.org/10.1130/B30174.1 |
| Date Other: | Fri, 1 Jan 2010 00:00 -0600 |
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