Free gas distribution and basal shear zone development in a subaqueous landslide – Insight from 3D seismic imaging of the Tuaheni Landslide Complex, New Zealand

Gross, Felix, Mountjoy, Joshu, Crutchley, Gareth J., Böttner, Christoph, Koch, Stephanie, Bialas, Jörg, Pecher, Ingo, Woelz, Susi, Dannowski, Anke, Micallef, Aaron, Huhn, Katrin and Krastel, Sebastian (2018) Free gas distribution and basal shear zone development in a subaqueous landslide – Insight from 3D seismic imaging of the Tuaheni Landslide Complex, New Zealand Earth and Planetary Science Letters, 502 . pp. 231-243. DOI 10.1016/j.epsl.2018.09.002.

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Abstract

Highlights

• 3D seismic imaging of an entire landslide complex.
• Shallow gas accumulation within and underneath Tuaheni Landslide Complex.
• Imaging of a basal shear zone within a subaqueous landslide complex.

Abstract

The Hikurangi margin is an active continental margin east of New Zealand's North Island. It is well recognized as a seismically active zone and is known for the occurrence of free gas and gas hydrates within the shallow sediments. A variety of subaqueous landslides can be observed at the margin, including the Tuaheni Landslide Complex off Poverty Bay. This slide complex has been interpreted previously as a slowly creeping landform, as its morphology and internal deformation is comparable to terrestrial earthflows and rock glaciers. In 2014, we acquired a high-resolution 3D seismic volume covering major parts of the Tuaheni South landslide. The 3D data show a variety of fluid migration indicators, free gas accumulations and manifestations of the base of gas hydrate stability in the pre-slide sedimentary units and the lower unit of the landslide system. The data also show that the landslide system is composed of an upper and lower unit that are separated by an intra-debris negative-polarity reflection. Free gas accumulations directly beneath the landslide units suggest that the debris acts as a boundary for rising fluids and only few migration pathways to the intra-debris reflector are observed in the distal parts of the landslide. Deformation within the landslide's debris is focused in the upper landslide unit, and we interpret the intra-debris reflector as a basal shear zone or ‘glide plane’ upon which the debris has been remobilized. The origin of the intra-debris reflector is unclear, but we suggest it could be a relatively coarse-grained horizon that would be prone to fluid flow focusing and the development of excess fluid pressure. Our seismic study provides one of the most detailed examples of a subaqueous landslide system and reveals insights into the fluid flow system and potential basal shear zone development of the Tuaheni Landslide Complex.

Document Type: Article
Additional Information: Access to the bathymetric and seismic data is through NIWA marine data repository (https:// marinedata.niwa.co.nz/project-map-sam/).
Keywords: Tuaheni Landslide Complex, subaqueous landslide, shallow free gas, basal shear zone, 3D seismic, P-Cable, RV Tangaroa
Research affiliation: MARUM
Kiel University > Kiel Marine Science
OceanRep > The Future Ocean - Cluster of Excellence
OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
Kiel University
Refereed: Yes
DOI etc.: 10.1016/j.epsl.2018.09.002
ISSN: 0012-821X
Related URLs:
Date Deposited: 20 Sep 2018 07:33
Last Modified: 04 Feb 2019 11:34
URI: http://eprints.uni-kiel.de/id/eprint/44040

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