My point exactly! There are huge debris flows in the subsurface and there have been dire predicitions of tsunami's resulting from a flank of the canari's and the hawaiin Islands colapsing. But there's not been such an event since the 50's and our views and technology have changed and grown significantly since then. So if one could demonstrate that there was OR was not an associated catastrophic debris flow offshore Indonesia then this would be of some consequence. Furthermore the there was a apparently a tsunami on the west coast of Sumatra as well as the east coast. Seems that the epicenter was on the east coast, but so there should be no rupture on the west coast, but there could be significan debris flows from such an earthquake on all coast.
Finally: I could go do my own homework but it's easier to post the question here: What was the hypocenter or depth of the initiation of the earthquake below the epicenter? Displacement theory suggest that if the fault's initial rupture was as at 10,000 meters below the sea, the magnitude of the surface rupture may not be great enough initiate such a tsunami.
Josh
-----Original Message-----
From: Tectonics & structural geology discussion list on behalf of Christopher Morley
Sent: Thu 1/20/2005 10:12 PM
To: [log in to unmask]
Cc:
Subject: Re: Earthquake
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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