| Abstract: | The amplitude of a bottom simulating reflection (BSR), which occurs near the phase boundary between gas hydrate-bearing sediments and underlying gas-filled sediments, strongly depends on the frequency content of a seismic signal, as well as the impedance contrast across the phase boundary. A strong-amplitude BSR, detectable in a conventional seismic profile, is a good indicator of the presence of free gas beneath the phase boundary. However, the BSR as observed in low-frequency multichannel seismic data is generally difficult to identify in high-frequency, single-channel seismic data.
To investigate the frequency dependence of BSR amplitudes, single-channel seismic data acquired with an air gun source at Blake Ridge, which is located off the shore of South Carolina, were analyzed in the frequency range of 10-240 Hz. The frequency-dependent impedance contrast caused by the velocity dispersion in partially gas saturated sediments is important to accurately analyze BSR amplitude. Analysis indicates that seismic attenuation of gas hydrate-bearing sediments, velocity dispersion, and a transitional base all contribute to the frequency-dependent BSR amplitude variation in the frequency range of 10-500 Hz. When velocity dispersion is incorporated into the BSR amplitude analysis, the frequency-dependent BSR amplitude at Blake Ridge can be explained with gas hydrate-bearing sediments having a quality factor of about 250 and a transitional base with a thickness of about 1 meter. |
| Genre: | USGS Numbered Series |
| ProdID: | 80218 |
| Citation Author: | Lee, Myung W. |
| Citation Contributing Office: | Geological Survey (U.S.) |
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| Citation Edition: | Version 1.0 |
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| Citation Language: | ENGLISH |
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| Citation Phsyical Description: | iii, 12 p. |
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| Citation Publisher: | Geological Survey (U.S.) |
| Citation Series: | Scientific Investigations Report |
| Citation Series Code: | SIR |
| Citation Series Number: | 2007-5091 |
| Citation Search Results Text: | Amplitude Variation of Bottom Simulating Reflection with Respect to Frequency - Transitional Base or Attenuation?; 2007; SIR; 2007-5091; Lee, Myung W. |
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| Citation Year: | 2007 |
| Type: | citation/reference |
| Text: | Amplitude Variation of Bottom Simulating Reflection with Respect to Frequency - Transitional Base or Attenuation?; 2007; SIR; 2007-5091; Lee, Myung W. |
| URL (THUMBNAIL): | http://pubs.er.usgs.gov/thumbnails/sir_2007_5091.jpg |
| URL (INDEX PAGE): | http://pubs.usgs.gov/sir/2007/5091/ |
| Date Other: | Tue, 14 Aug 2007 00:00 -0500 |
| Publisher: | Geological Survey (U.S.) |
