--> Distribution of faulting and gas hydrates in the southern Hikurangi Margin

AAPG Asia Pacific Region Geosciences Technology Workshop:
Gas Hydrates – From Potential Geohazard to Carbon-Efficient Fuel?

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Distribution of faulting and gas hydrates in the southern Hikurangi Margin

Abstract

The Hikurangi Margin hosts New Zealand’s largest gas hydrate province, extending over 50,000 km2, across an extremely varied, tectonically active subduction zone. The region is characterized by a series of accretionary ridges connected to deep-seated thrust faults that generally do not reach the gas hydrate stability zone. At shallower depths the anticlinal ridges are frequently associated with localized extensional deformation and closely spaced normal faults that extend up to the seafloor. Recently completed 2D models from the southern Hikurangi Margin suggest that in some locations deeply penetrating thrust faults play a significant role in supplying gas from depth to the hydrate stability field, facilitating and channeling upward fluid flux. This results in the formation of concentrated hydrate accumulations in anticlinal thrust ridges. However; some uncertainty remains as to the relationship between faulting and the occurrence of gas hydrates at a regional scale. The abundance of seismic data along the Hikurangi Margin allows us to examine this relationship and determine whether faults are a controlling factor in the distribution of gas hydrates. Through mapping anomalous amplitudes, indicative of gas hydrates, and bottom simulating reflections (BSRs) in seismic data we can determine the distribution of hydrate accumulations across the region. Correlating this information with the occurrence of thrust and normal faults reveals an interesting relationship between the tectonic setting and hydrate system. In addition, the position of observed flares in the water column demonstrates the role that shallow faults play in channeling focused fluid flow from the GHSZ up towards the seafloor. Better constraining the relationship between faults, heatflow, fluid flux and seafloor venting may help further our understanding of the interconnectivity of processes across the Hikurangi Margin subduction zone and whether fluid flux plays any role in earthquake generation.