Amplitude Variation of Bottom Simulating Reflection with Respect to Frequency - Transitional Base or Attenuation?
Scientific Investigations Report
2007-5091
By: Myung W. Lee
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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.
Suggested Citation
Lee, M.W., 2007, Amplitude Variation of Bottom Simulating Reflection with Respect to Frequency - Transitional Base or Attenuation? (Version 1.0): U.S. Geological Survey Scientific Investigations Report 2007-5091, iii, 12 p., https://doi.org/10.3133/sir20075091.
ISSN: 2328-0328 (online)
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Amplitude Variation of Bottom Simulating Reflection with Respect to Frequency - Transitional Base or Attenuation? |
| Series title | Scientific Investigations Report |
| Series number | 2007-5091 |
| DOI | 10.3133/sir20075091 |
| Edition | Version 1.0 |
| Year Published | 2007 |
| Language | ENGLISH |
| Publisher | Geological Survey (U.S.) |
| Contributing office(s) | U.S. Geological Survey |
| Description | iii, 12 p. |