The Hikurangi Margin off the east coast of the North Island (Te Ika-a-Māui) is a tectonically active subduction zone and the location of New Zealand’s largest gas hydrate province. Faults are internally complex volumetric zones that may play a significant role in the migration of fluids beneath the seafloor. The combined processes of deformation and fluid migration result in the formation of concentrated hydrate accumulations along accretionary ridges. It is not fully understood to what extent faults control fluid migration along the Hikurangi Margin, and whether deep-seated thrust faults provide a pathway for thermogenic gas to migrate up from sources at depth. Using 2D models based on seismic data from the region we investigated the role of thrust faults in facilitating fluid migration and contributing to the formation of concentrated gas hydrates. By altering permeability properties of the fault zones in these transient state models we can determine whether faults are required to act as fluid flow pathways. In this study we focus on two study sites offshore southern Wairarapa, using realistic yet simplified fault geometries derived from 2D seismic lines. The results of these models allow us to start to disentangle the complex relationship between fault zone structure, permeability, geometry, fluid migration and gas hydrate formation. Based on the model outputs we propose that faults act as primary pathways facilitating fluid migration and are critical in the formation of concentrated gas hydrate deposits.

中文翻译：

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调查断层在新西兰南部Hikurangi边缘沿流体运移和天然气水合物形成中的作用

北岛东海岸（TeIka-a-Māui）的Hikurangi边缘是构造活跃的俯冲带，是新西兰最大的天然气水合物省的所在地。断层是内部复杂的体积带，可能在海底以下流体的迁移中起重要作用。变形和流体运移的综合过程导致沿增生脊形成浓缩的水合物堆积。尚未完全了解断层在多大程度上控制了流体沿Hikurangi边缘的运移，以及深层的逆冲断层是否为热成气从深处的源向上迁移提供了途径。使用基于该地区地震数据的二维模型，我们研究了逆冲断层在促进流体运移和促进天然气水合物形成中的作用。通过改变这些瞬态模型中断层带的渗透性，我们可以确定是否需要断层作为流体流动路径。在这项研究中，我们集中在怀拉拉帕南部海域的两个研究地点，使用了从2D地震线得出的逼真的但简化的断层几何形状。这些模型的结果使我们开始理清断层带结构，渗透率，几何形状，流体运移和天然气水合物形成之间的复杂关系。