Phyllis Yu

PhD Candidate

Madsen Building (F09), Room 358
Phone: +61 (0)412 121 190
Fax: +61 2 9351 2442
Email:

Supervisor
Associate Professor Thomas Hubble

Associate Supervisor
Associate Professor David Airey

Research

PhD: Submarine landslides on the mid-slope of the East Australian Continental Margin: Implications for tsunamigenesis

In recent years, the existence of submarine landslides, their roles in seafloor morphology, and their capability in generating tsunamis have been recognised. In the Australian context, a large number of features associated with such failures have been observed on the East Australian continental margin during a voyage in 2008 abroad CSIRO’s oceanographic ship, the RV Southern Surveyor (Boyd et al, 2009). The mid- and lower-slopes appear to have experienced the largest slides in terms of the volume of failed material involved.

A range of dredge samples, including potential slide-plane material, have been collected within the study area located offshore southern Queensland and northern New South Wales during the aforementioned voyage. Sedimentological analysis indicates that the margin is composed primarily of normally-consolidated, cohesive, calcareous sandy-silts. Preliminary bulk dates derived from biostratigraphic data suggest that the failure events and episode of margin dissection are geologically young, dating around the Neogene (more specifically, Mid- to Late-Miocene). Geotechnical parameters such as cohesion, friction angle and bulk unit density have been obtained using classical soil mechanics methodologies.

High-resolution multibeam data was also collected upon the same voyage. Various slide features such as slump scars and canyons appear to be ubiquitous throughout the study area, across the entire continental margin, from the upper- to the lower-slope. On the mid- to lower-slopes, the larger slides are generally rotational, low-angle, and some present strong evidence of retrogression with lower slope failures propagating upslope. Using parameters provided by geotechnical testing and geometry provided by multibeam data, preliminary classical geomechanical models suggest that the margin is inherently stable, and that destabilising forces equivalent to a magnitude-6 to 7 earthquake are required to induce failure.

This study will investigate the physical characteristics of the East Australian continental margin, the potential causes of mass failure events in such a setting, and the factors that dictate their likelihood of reoccurrence. The Mid-Miocene Antarctic Icesheet expansion is suspected to have played a part in destabilising the slopes by providing an influx of cold, equator-bound bottom water that is responsible for causing erosion from the mid- and lower-slopes of the Australian continental margin in the Tasman Sea. This would contribute to the destabilisation of the slopes by removal of material from the toe of the continental slope sediment wedge. Biostratigraphic dates are also in support of Boyd et al.’s (2009) conclusion based on sedimentation rates, that some of these masses were mobilised during the most recent sea-level lowstand. These dates are contemporaneous across separate but adjacent slides, and therefore consistent with the notion that the failures were triggered by a single short-term event, such as an earthquake.

Publications

Clarke, S., Airey, D. W., Yu, P., Hubble, T. (2011). Submarine Landslides on the South-Eastern Australian Margin. Australian Geomechanics Society Sydney Chapter Symposium October 2011. Sydney, Australia, Australian Geomechanics Society: 27-38.

Clarke, S., Hubble, T., Airey, D.W., Yu, P., Boyd, R., Keene, J. B., Exon, N., Gardner, J., Shipboard Party SS12/2008 (2012). Submarine Landslides on the Upper Southeast Australian Passive Continental Margin – Preliminary Findings. Submarine Mass Movements and Their Consequences. . Y. Yamada, K. Kawamura, K. Ikehara, Y. Ogawa, R. Urgeles, D. Mosher, J. Chaytor, M. Strasser. Kyoto, Springer. 31: 55-66.

Hubble, T., Yu, P., Airey, D.W., Clarke, S., Boyd, R., Keene, J. B., Exon, N., Gardner, J., Shipboard Party SS12/2008 (2012). Physical Properties and Age of Continental Slope Sediments Dredged from the Eastern Australian Continental Margin – Implications for Timing of Slope Failure. Submarine Mass Movements and Their Consequences. Y. Yamada, K. Kawamura, K. Ikehara, Y. Ogawa, R. Urgeles, D. Mosher, J. Chaytor, M. Strasser. Kyoto, Springer. 31: 43-54.

Conference Proceedings and Abstracts

Clarke, S., Hubble, T., Airey, D., Yu, P., et al. (submitted) Geologically recent submarine landslides from the southeastern Australian continental margin - preliminary findings, Abstract. 2012 Ocean Science Meeting, AGU, Salt Lake City, Utah, 20-24 Feb.

Hubble, T., Yu, P., et al. (submitted) A conceptual model for the onset and occurrence of submarine landslides on the southeastern Australian continental margin, Abstract. 2012 Ocean Science Meeting, AGU, Salt Lake City, Utah, 20-24 Feb.

Hubble, T., Yu, P., et al. (2010) Physical properties and age of mid-slope sediments dredged from the Eastern Australian Continental Margin and the implications for continental margin erosion processes, Abstract OS13E-1297 presented at 2010 Fall Meeting, AGU, San Francisco, Calif., 13-17 Dec.