Understanding slow-slipping submarine landslides: 3D seismic investigations of the Tuaheni landslide complex

• Applicants: Dr. Jörg Bialas; Professor Dr. Sebastian Krastel
• Subject Area: Geophysics
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 254069062

• Final Report Year: 2018

Final Report Abstract

Slow creeping landslides and earthflows are common landforms, which can be observed in the terrestrial and extra-terrestrial realm. In the subaqueous realm, such landforms have been proposed but have never been documented. In comparison to terrestrial-style earthflows, subaqueous landslides are not mainly controlled by water saturation and resulting shear strength reduction. Hence, studying the agents, responsible for subaqueous mass movements, is essential to understand rapid failures or slow slipping landslides. The Tuaheni Landslide Complex offshore New Zealand’s North Island shows a morphology and deformation fabrics like lateral spreads and crevasses, which were only known from terrestrial-style earthflows and rock glaciers. This makes it to one of the best candidates, which could show a slow creeping behavior, implying that not all subaqueous landslides show a rather rapid failure mechanism. The aim of this study was to evaluate the potential driving mechanisms by imaging its internal deformation fabrics, free gas- and gas hydrate distribution within and underneath the slide complex. In order to obtain the required data, a high-resolution P-Cable 3D seismic volume and several overview 2D seismic profiles have been acquired during RV Tangaroa cruise TAN1404 (April-May 2014) of the Tuaheni Landslide Complex and the Hikurangi margin. The new data show that the Tuaheni Landslide Complex is a stacked landslide deposit, which shows different slide bodies. A key observation is an internal reflector, which is interpreted as a potential basal shear surface, commonly observed in terrestrial slow-slipping landslides. The new data does not show any indicators for gas hydrates within the slide complex, making the presence of a postulated hydrate glacier unlikely. As nearly 50% of the landslide’s debris is located within the gas hydrate stability zone, free gas/fluid migration could also play an important role in slide remobilization. In some parts in the distal sector of the landslide complex, we were able to identify faults with clear indicators for gas/fluid migration. Next to the debris of Tuaheni Landslide complex, we identified an intensive network of normal faults underneath the distal extents of the landslide. Mechanisms that may have contributed to the development of the normal faults in the Hikurangi margin include uplift and gravitational collapse and/or flexural bending of the upper plate and residual extensional strain, which is induced into the marine forearc by rotation of tectonic blocks around nearby poles. This work adds another piece of evidence that normal faults play an important role in the seismotectonic evolution of accretionary margins. The acquired seismic lines and the 3D seismic volume are an essential contribution to the scientific community working on subaqueous mass movements. The dataset is a basis for several projects addressing slope stability and potentially slow creeping landforms. During SO247 and IODP-Leg 372, the landslide complex was sampled by means of deep drilling and LWD measurements. This study is the basis for all these investigations, which will eventually make TLC to one of the best studied subaqueous landslide complexes worldwide.

Publications

• (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 502 231-243
  Gross, F., Mountjoy, J.J., Crutchley, G., Böttner, C., Koch, S., Bialas, J., Pecher, I., Woelz, S.,
  
• 2014. NIWA Voyage Report TAN1404: SCHLIP-3D: submarine clathrate hydrate landslide imaging project: Auckland, New Zealand (National Institute of Water and Atmospheric Research)
  Mountjoy, J., Krastel, S., Crutchley, G., Dannonski, A., Graw, M., Koch, S., Micallef, A., Quinn, W., and Woelz, S.
  
• (2015) The Tuaheni Landslide Complex – First results from the 3D seismic perspective In: 7th International Symposium on Submarine Mass Movements and their Consequences, 01.11.- 04.11.2015, Wellington, New Zealand
  Gross, F., Krastel, S., Mountjoy, J., Crutchley, G., Pecher, I.
  
• (2016) Shallow Gas and the Development of a Weak Layer in Submarine Spreading, Hikurangi Margin (New Zealand). In: Geoffroy Lamarche et al. (Eds.): Submarine Mass Movements and their Consequences Bd. 41. Cham: Springer International Publishing (Advances in Natural and Technological Hazards Research), S. 419–426
  Micallef, A., Mountjoy, J. J., Krastel, S., Crutchley, G., Koch, S.
  
• (2016) Submarine creeping landslide deformation controlled by the presence of gas hydrates: The Tuaheni Landslide Complex, New Zealand [Talk] In: EGU General Assembly 2016, 17.-22.04.2016, Vienna, Austria
  Gross, F., Mountjoy, J., Crutchley, G., Koch, S., Bialas, J., Pecher, I., Woelz, S., Dannowski, A., Carey, J., Micallef, A., Böttner, C., Huhn, K. und Krastel, S.
  
• 2016. Large creepy landslides controlled by gas hydrates? Rheological control or cyclic gas flux from the base of hydrate stability. Gordon Research Conference, Galveston, Texas, 28 February–4 March 2016
  Mountjoy, J.J., Krastel, S., Gross, F., and Pecher, I.
  
• (2017) An analysis of marine forearc extension on the northern Hikurangi subduction margin using high-resolution 3D seismic data. In: Subduction Interface Processes Conference., 18.04.-21.04.2017, Barcelona, Spain
  Böttner, C., Gross, F., Geersen, J. M., Mountjoy, J., Crutchley, G. und Krastel, S.
  
• (2017) Marine forearc extension in the Hikurangi Margin: New insights from high-resolution 3D seismic data. In: EGU General Assembly 2017, 23.-28.04.2017, Vienna, Austria
  Böttner, C., Gross, F., Geersen, J., Mountjoy, J., Crutchley, G. und Krastel, S.
  
• (2018) Marine forearc extension in the Hikurangi margin: New insights from high-resolution 3-D seismic data. Tectonics, 37
  Böttner, C., Gross, F., Geersen, J., Crutchley, G. J., Mountjoy, J. J., Krastel, S.
  
• (2018). International ocean discovery program expedition 372 preliminary report creeping gas hydrate slides and Hikurangi LWD. Integrated Ocean Drilling Program: Preliminary Reports (372), 1-35
  Pecher, I. A., Barnes, P. M., LeVay, L. J., Bourlange, S. M., Brunet, M. M. Y., Cardona, S., ... Elger, J.