Understanding gas distribution beneath Hydrate Ridge, offshore Oregon: combining high-resolution 3D seismic data with various 2D seismic profiles acquired at different frequencies
Abstract
We present 3D seismic data that were acquired over Hydrate Ridge, offshore Oregon, during cruise TN220 aboard R/V Thompson in 2008 in order to better understand dynamics of gas migration through the gas hydrate stability zone. A surface area of 3 by 6 km was covered with the low-fold, high-resolution P-Cable system that comprised two 150 cubic inch airguns and two paravanes towing 10 single channel streamers. A standard near-trace processing sequence including trace editing, trace interpolation and 3D Kirchhoff migration was applied. Supplementing the 3D data are 2D profiles that were acquired with various source types (airgun, GI gun and sparker) during R/V Sonne Cruise SO150 in 2000. Due to tuning effects of thin gas layers, the strength of the bottom simulating reflection is shown to be strongly dependent on seismic frequency. Synthetic seismic modeling of thin gas layers at different frequencies allowed for a comparison between synthetic amplitudes and real amplitude variations in the different datasets. This ultimately enabled predictions of the thickness of the gas column beneath the ridge to be made, which is estimated to vary between 3 and 11 m along a 2 km segment spanning the western flank of the southern ridge. Combining these results with the 3D architecture of the sub seafloor revealed from the P-Cable data will lead to an improved understanding of gas migration dynamics and gas distribution beneath Hydrate Ridge.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMOS53A1360C
- Keywords:
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- 3004 MARINE GEOLOGY AND GEOPHYSICS / Gas and hydrate systems;
- 3025 MARINE GEOLOGY AND GEOPHYSICS / Marine seismics