Title: Terrestrial-style slow-moving earthflow kinematics in a submarine landslide complex
Author: Mountjoy, Joshu J.; McKean, Jim; Barnes, Philip M.; Pettinga, Jarg R.
Source: Marine Geology. 267: 114-127.
Description: Morphometric analysis of Simrad EM300 multibeam bathymetric
DEMs reveals details of deformation patterns in a ~145 km2 submarine
landslide complex that are commonly associated with slow-moving
earthflows in terrestrial settings. This mode of failure, where
existing landslide debris is remobilised repeatedly along discrete
shear boundaries and is progressively conveyed through the complex,
has not previously been recognised in the submarine environment.
The kinematics contrast with the more traditional models of submarine
landslide complex development in which repeated catastrophic
failures each mobilise new source material to form a composite
stacked landslide deposit. In our study of the Tuaheni landslide
complex on the Hikurangi Margin of New Zealand, remobilisation
has formed boundary shear zones imaged at the seafloor surface
in multibeam data, and at depth in multichannel seismic reflection
data. A significant amount of internal deformation has occurred
within the debris streams. Phases of deformation appear to be
partitioned longitudinally as extensional and contractional zones
rooted into a basal decollement, and laterally with strikeslip
shears partitioning discrete debris streams. While slow-moving
terrestrial earthflows are activated by fluctuating piezometric
levels typically controlled by precipitation, different processes
cause the equivalent mobility in a submarine earthflow. Elevated
pore pressures in submarine earthflows are produced by processes
such as earthquake-generated strong ground motion and/ or gas/fluid
release. Earthflow movement in submarine settings is prolonged
by slow dissipation in pore pressure.
Keywords: submarine earthflow, mass transport complex, morphometric analysis, landslide kinematics, EM300 multibeam, submarine geomorphology
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Mountjoy, Joshu J.; McKean, Jim; Barnes, Philip M.; Pettinga, Jarg R. 2009. Terrestrial-style slow-moving earthflow kinematics in a submarine landslide complex. Marine Geology. 267: 114-127..