| Abstract: | Differential pressure affects elastic velocities and Poisson?s ratio of sediments in such a way that velocities increase as differential pressure increases. Overpressured zones in sediments can be detected by observing an increase in Poisson?s ratio with a corresponding drop in elastic velocities. In highly overpressured sands, such as shallow water flow sands, the P-to S-wave velocity ratio (Vp/Vs) is very high, on the order of 10 or higher, due to the unconsolidated and uncemented nature of sediments. In order to predict elastic characteristics of highly overpressured sands, Biot-Gassmann theory by Lee (BGTL) is used with a variable exponent n that depends on differential pressure and the degree of consolidation/compaction. The exponent n decreases as differential pressure and the degree of consolidation increases, and, as n decreases, velocity increases and Vp/Vs decreases. The predicted velocity ratio by BGTL agrees well with the measured velocity ratio at low differential pressure for unconsolidated sediments. |
| Genre: | USGS Numbered Series |
| ProdID: | 53149 |
| Citation Author: | Lee, Myung W. |
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| Citation Edition: | Version 1.0 |
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| Citation Language: | ENGLISH |
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| Citation Phsyical Description: | 10 p. |
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| Citation Series: | Bulletin |
| Citation Series Code: | B |
| Citation Series Number: | 2214 |
| Citation Search Results Text: | Elastic properties of overpressured and unconsolidated sediments; 2003; B; 2214; Lee, Myung W. |
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| Citation Year: | 2003 |
| Type: | citation/reference |
| Text: | Elastic properties of overpressured and unconsolidated sediments; 2003; B; 2214; Lee, Myung W. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/usgs_thumb.jpg |
| URL (INDEX PAGE): | http://pubs.usgs.gov/bul/b2214/ |
| Date Other: | Sat, 1 Nov 2003 00:00 -0600 |
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