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

99-06990 Trehu 99 -07205 Bangs建议的项目是对俄勒冈州近海大陆边缘卡斯卡迪亚增生复合体上的海伯利脊顶部的一个9 x4公里区域进行高分辨率三维海洋地震勘探。 该调查将使用海底地震仪来优化地震信号的记录，并将侧重于绘制这一高流体通量区域的增生沉积物中存在的天然气水合物。 其他目标集中在定义天然气水合物的稳定性条件;估计天然气水合物和游离气体的体积，与游离气体被困在底部模拟反射层（BSR）与天然气水合物的存在;定义流体通量的路径及其在天然气水合物形成的重要性;和斜坡稳定性（或不稳定性）有关的卡斯卡迪亚边缘的天然气水合物的存在。 本研究所要检验的具体假设包括：1）明亮的地层反射是否代表聚焦流体流动的发育带; 2）在研究区的背斜内的先前多通道工作中成像的双BSR是否代表响应于褶皱的水合物的不稳定性; 3）折射到达的层析反演是否能够成像其中存在游离气的子BSR体积;水合物和游离气的存在是否影响增生复合体的力学性质，从而影响边坡稳定性和形态。 这项工作将为海参崴

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.***