[Physltest] [Phys-L] Re: earthquake

[Brian Whatcott <betwys1@SBCGLOBAL.NET>]

At 05:50 PM 12/31/2004, Jim Green, you wrote:
> ///
> > At 1:28 PM -0700 12/30/04, Jim Green wrote:
> > > If a piece of the Earth sank, where did 600 mi x 100 mi x 30 ft go?  What
> > > did it displace?
> > >
> > > Jim
>
> I haven't seen a helpful answer to the original question.  Any land motion
> took place under water.  It didn't fall from a cliff or fall into a
> trench.  The boundary between plates moved.  And I don't see why there is
> wave motion.  If the land sank, where did it go?

///
> Jim Green

Here's a plausible description.   The current model of continental motion
  has it that plates of Earth surface move coherently.    They are motivated
in part by upwelling of material from the hot, more fluid depths. Where
  plate motion  encroaches on an adjacent plate, one or the other dives.
The subduction zone is not friction-free. An earthquake such as the one in
review presently, was reported to indicate a depth of about 10 km for the
origin of the tremor. One can easily suppose that elastic strain energy is
stored in the plate, until the latch in the subduction zone gives way.
At this point, one expects to see the plate edge move roughly as far
  as the upwelling zone has pushed the far edge of the same plate
since the last major slip.
The sound of your nails scratching on a blackboard has its counterpart
  in the 0.05 Hz fundamental 'squeal' of a plate moving on another.
There may be  theoretical justification for the talk of 30 meter drops
in a long slab of plate perimeter, or there may not be, but stick-slip
  motion of plate  boundaries is more or less a given.
  Nobody, I take it, would seriously doubt this as a cause for Tsunami
events.



Brian Whatcott    Altus OK    Eureka!
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