Geophysical and geochemical data indicate there is abundant fluid expulsion in the Nootka fault zone (NFZ) between the Juan de Fuca and Explorer plates and the Nootka continental slope. Here we combine observations from >20 years of investigations to demonstrate the nature of fluid‐flow along the NFZ, which is the seismically most active region off Vancouver Island. Seismicity reaching down to the upper mantle is linked to near‐seafloor manifestation of fluid flow through a network of faults. Along the two main fault traces, seismic reflection data imaged bright spots 100–300 m below seafloor that lie above changes in basement topography. The bright spots are conformable to sediment layering, show opposite‐to‐seafloor reflection polarity, and are associated with frequency reduction and velocity push‐down indicating the presence of gas in the sediments. Two seafloor mounds ~15 km seaward of the Nootka slope are underlain by deep, nonconformable high‐amplitude reflective zones. Measurements in the water column above one mound revealed a plume of warm water, and bottom‐video observations imaged hydrothermal vent system biota. Pore fluids from a core at this mound contain predominately microbial methane (C₁) with a high proportion of ethane (C₂) yielding C₁/C₂ ratios <500 indicating a possible slight contribution from a deep source. We infer the reflective zones beneath the two mounds are basaltic intrusions that create hydrothermal circulation within the overlying sediments. Across the Nootka continental slope, gas hydrate‐related bottom‐simulating reflectors are widespread and occur at depths indicating heat flow values of 80–90 mW/m².

中文翻译：

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沿Nootka断层带和大陆坡集中的流体流动，Explorer-Juan de Fuca板块边界

地球物理和地球化学数据表明，在胡安德富卡和探险家板块与Nootka大陆斜坡之间的Nootka断层带（NFZ）中有大量的流体排出。在这里，我们结合了超过20年的调查结果，以证明沿着NFZ的流体流动的本质，NFZ是温哥华岛附近地震最活跃的地区。地震作用一直延伸到上地幔，这与通过断层网络的近海流体流动有关。沿着两条主要断层迹线，地震反射数据成像了海底以下100-300 m的亮点，这些亮点位于地下室地形变化的上方。亮点适合沉积物分层，显示与海底相反的反射极性，并与频率降低和速度下推相关联，表明沉积物中存在气体。Nootka斜坡向海约15 km处的两个海底丘被深的，不整合的高振幅反射带所覆盖。在一个土墩上方的水柱中的测量结果显示出一缕温水，而底部视频的观测结果则为热液喷口系统生物群成像。在此堆堆中，来自岩心的孔隙液主要含有微生物甲烷（C₁）具有高比例的乙烷（C ₂），产生的C ₁ / C ₂比<500，表明可能是由深层来源引起的轻微贡献。我们推断这两个土墩下方的反射带是玄武质侵入体，在上覆沉积物中产生了热液循环。在Nootka大陆斜坡上，与天然气水合物有关的底部模拟反射器分布广泛，并出现在指示热流值为80–90 mW / m ^2的深度处。