3-D Seismic Imaging of an Active Margin Hydrate System - Oregon Continental Margin

bangs推荐的项目是对位于俄勒冈大陆边缘Cascadia增生复合体的水合物山脊顶部9 x 4公里区域进行高分辨率三维海洋地震调查。该调查将使用海底地震仪（OBS）来优化地震信号的记录，并将重点放在绘制该地区高流体通量的沉积沉积物中天然气水合物的存在。其他目标集中在确定天然气水合物的稳定性条件；利用与天然气水合物相关的底部模拟反射器（BSR）估算天然气水合物和游离气体积；流体通量路径及其在天然气水合物形成中的重要性以及与卡斯卡迪亚边缘天然气水合物存在有关的斜坡稳定性（或不稳定性）。本研究需要验证的具体假设包括：1)明亮的地层反射是否代表流体集中流动的发育带；2)研究区背斜内多通道双BSR成像是否代表水合物在褶皱作用下的不稳定；3)折射到达层析成像能否反演出存在游离气体的亚bsr体积；4)水合物和游离气体的存在是否会影响堆积复合体的力学性质，从而影响边坡的稳定性和形态。这项工作将为拟议的海洋钻探计划（ODP提案546-Full）在水合物脊上的钻探提供三维地层和构造背景，旨在“地面真相”与天然气水合物形成和稳定性相关的因素

99-06990 Trehu99-07205 BangsRecommended project is for a high-resolution, 3-D marine seismic survey of a 9 x 4 km area on the crest of Hydrate Ridge, on the Cascadia accretionary complex of the offshore Oregon continental margin. The survey will use ocean bottom seismometers (OBS's) to optimize recording of the seismic signals, and will focus on mapping the presence of gas hydrate within the accretionary sediments in this region of high fluid flux. Other goals center on defining the gas hydrate stability conditions; estimation of gas hydrate and free gas volumes, with the free gas trapped beneath bottom simulating reflectors (BSR's) associated with gas hydrate presence; defining pathways of fluid flux and their importance in gas hydrate formation; and slope stability (or instability) related to gas hydrate presence on the Cascadia margin. Specific hypotheses to be tested by the research include: 1) do bright stratigraphic reflections represent developing zones of focused fluid flow; 2) does a double BSR imaged in previous multichannel work within an anticline in the study region represent destabilization of hydrate in response to folding; 3) can tomographic inversion of refracted arrivals image the sub-BSR volume in which free gas is present; and 4) does the presence of hydrate and free gas affect the mechanical properties and thus slope stability and morphology of accretionary complexes. This work will provide the 3-dimensional stratigraphic and structural context for the proposed Ocean Drilling Program drilling (ODP proposal 546-Full) on Hydrate Ridge, which is designed to "ground truth" the factors related to gas hydrate formation and stability.***