Velocity structure of a bottom simulating reflector offshore Peru: Results from full waveform inversion
Earth and Planetary Science Letters
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Abstract
Much of our knowledge of the worldwide distribution of submarine gas hydrates comes from seismic observations of Bottom Simulating Reflectors (BSRs). Full waveform inversion has proven to be a reliable technique for studying the fine structure of BSRs using the compressional wave velocity. We applied a non-linear full waveform inversion technique to a BSR at a location offshore Peru. We first determined the large-scale features of seismic velocity variations using a statistical inversion technique to maximise coherent energy along travel-time curves. These velocities were used for a starting velocity model for the full waveform inversion, which yielded a detailed velocity/depth model in the vicinity of the BSR. We found that the data are best fit by a model in which the BSR consists of a thin, low-velocity layer. The compressional wave velocity drops from 2.15 km/s down to an average of 1.70 km/s in an 18m thick interval, with a minimum velocity of 1.62 km/s in a 6 m interval. The resulting compressional wave velocity was used to estimate gas content in the sediments. Our results suggest that the low velocity layer is a 6-18 m thick zone containing a few percent of free gas in the pore space. The presence of the BSR coincides with a region of vertical uplift. Therefore, we suggest that gas at this BSR is formed by a dissociation of hydrates at the base of the hydrate stability zone due to uplift and subsequently a decrease in pressure.
Suggested Citation
Pecher, I., Minshull, T., Singh, S., and von Huene, R.E., 1996, Velocity structure of a bottom simulating reflector offshore Peru: Results from full waveform inversion: Earth and Planetary Science Letters, v. 139, no. 3-4, p. 459-469, https://doi.org/10.1016/0012-821X(95)00242-5.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Velocity structure of a bottom simulating reflector offshore Peru: Results from full waveform inversion |
| Series title | Earth and Planetary Science Letters |
| DOI | 10.1016/0012-821X(95)00242-5 |
| Volume | 139 |
| Issue | 3-4 |
| Year Published | 1996 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Earth and Planetary Science Letters |
| First page | 459 |
| Last page | 469 |