The notion of giant slides triggered by an earthquake
as a cause of the tsunami is interesting, - the
modelling associated with landslides associated with
volcanic islands is well known. However the scale of
debris flows on continental margins may not be so well
known to many structural geologists, so I thought I
would chip in here with the following: - I have been
recently mapping some 3D seismic data deepwater
offshore Brunei, and there is one debris flow at the
seafloor today - (so it is well imaged), that is about
120 km long, and 50-80 km wide, and in places tens of
metres thick. It is very easily identified from less
disturbed parts of the seafloor by the very irregular
rugged surface topography caused by entrained blocks.
Compared with say 10 m vertical displacement of the
seafloor along a 100 km surface fault, the volume of
material in the debris flow capable of displacing
water is much greater. However one problem with this
particular debris flow is understanding whether it was
a single catastrophic event or an amalgamation of
events, and mixed fast and slow creep processes.
Chris
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