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Re: More questions on the Burma microplate (allegedly where the quake occurred)



Ok, now I don't mean to sound rude but have you tried Google? I typed in
"burma microplate" both with and with out the quotes and got a whole slough
of hits. Most useful were the alternative keywords I came up with simply by
reading the headers. For instance I got Burma block and Burma Plate,
Malacca-Burma block, West Burma Block. I could probably come up with more if
I searched harder. Anyway I eventually came across a blog which had pictures
and I traced them back to the source, and voila:
http://earthquake.usgs.gov/eqinthenews/2004/usslav/

Cheers,
Christopher

----- Original Message ----- 
From: "Dora Smith" <villandra@austin.rr.com>
To: "Dora Smith" <villandra@austin.rr.com>; "DML" <dinosaur@usc.edu>
Sent: Friday, December 31, 2004 10:52 PM
Subject: Re: More questions on the Burma microplate (allegedly where the
quake occurred)


> John Milson, in a chapter for a forthcoming book on Sumatra,
> http://www.es.ucl.ac.uk/people/milsom/smtrntct.htm, doesn't mention the
> Burma plate either - or the Sunda plate, atleast by name.
>
> He says that the fault-ridden zone between the Java trench and the Sumatra
> Fault, which he calls the forearc region, must be separated from both the
> "Indian Ocean" and "Eurasia".    He says it is often called a sliver plate
> but to call it a plate suggests that it has a degree of "strength and
> rigidity" that the long and narrow strip does not have.   He also says
that
> any analysis of subduction beneath Sumatra must take into account the
> probability of independent movement of fragments in this zone.
>
> We have another academic geologist who appears not to have heard of a
"Burma
> plate".
>
> I wonder what these two would say if I contact them, tell them to look at
> those NEIS web pages,  and ask what's the Burma plate?   I think I'll try
> it.    (Grin)
>
> So is the forearm strip the same thing as the "Burma plate"?
>
>
> Yours,
> Dora Smith
> Austin, Texas
> villandra@austin.rr.com
> ----- Original Message -----
> From: "Dora Smith" <villandra@austin.rr.com>
> To: "DML" <dinosaur@usc.edu>
> Sent: Friday, December 31, 2004 8:50 PM
> Subject: More questions on the Burma microplate (allegedly where the quake
> occurred)
>
>
> > Most ot what I'm finding on the Burma microplate is confusion.   Someone
> > sent me a bunch of links he thought would help; one link doesn't work,
one
> > is to that ol' NEIS chart, and the others are to small textual
> descriptions
> > of the plate.
> >
> > I have  Danny Hilman Natawidjaja's 2002 dissertation, "Neotectonics of
the
> > Sumatran Fault And
> > Paleogeodesy of the Sumatran Subduction Zone" , at
> >
>
http://etd.caltech.edu/etd/available/etd-05222003-155554/unrestricted/DHN_Th
> > esis.pdf.
> >
> > Natawidjaja identified and  mapped every fault on the island of Sumatra
> and
> > between the Sumatra fault and the subduction trench.   He discusses all
of
> > the geologic features.   He never mentions a Burma plate.   He doesn't
say
> > it doesn't exist; he literally never mentions it, though his work is
> > extremely recent.   I'd call that a good argument to think that many
> > geologists would have as little idea as I do what the NEIS descriptions
of
> > the earthquake are  talking about.
> >
> > Natawidjaja does mention an outer arc sliver, and describes it as a
> separate
> > piece of plate - is that the same thing as this Burma plate?
> >
> > Apparently the answer to the question about what is sliding in relation
to
> > what, is that, actually, the plates aren't sliding in a direction
parallel
> > to the subduction fault, at the trench, nor along one fault between two
> > plates; nor along two faults between three plates.    The two plates
> > converge in a very oblique angle.   Like apparently most oblique
> subduction
> > faults, the subduction trench takes perpendicular motion and a complex
> > lacework of strike/slip faults between the trench and the central ridge
> take
> > motion parallel to the subduction trench.    In the case of the Sunda/
> Java
> > subduction faults, a lacework of faults large and small between the
trench
> > and the Sumatra fault in the central mountain range take the motion
> parallel
> > to the trench.
> >
> > Natawidjaja appears to suggest that more of the motion is absorbed off
of
> > the coast of Sumatra than on Sumatra, but I'm not very clear on that
> because
> > I've only read two chapters of his long thesis so far.   He explains
that
> > one reason to believe that only so much displacement has occurred on the
> > island of Sumatra since it began only a few million years ago, is that
the
> > rest of it occurs offshore.
> >
> > The Burma plate is supposed to be separating from the Sunda plate.
> > Natawidjaja's version of that is that there is spreading occurring at
> > various places on the island of Sumatra and between the island and the
> > subduction trench, and that the spreading increases in the Andaman Sea
to
> > the north.
> >
> > North of Sumatra, the north-south aspect of the oblique convergence of
the
> > plates is handled by a network of faults in the Andoman Sea and a major
> > fault in Burma.
> >
> > Natawidjaja does not mention a Sunda plate, either.
> >
> > I am also partway through the Hall article - so far he mentions the
Burma
> > plate but does not properly discuss it.    He appears to be far less
> > interested in teh details of what is taking place than Natawidjaja is.
> >
> > Does anyone have any ideas?
> >
> > Is there anything about the boundaries of the Burma plate that would
> enable
> > me to identify its boundaries on a detailed chart of the faults of the
> area?
> >
> > By the way, since all of the faults between Sumatra and the subduction
> > trench have been mapped within the past few years, it should not be
> > difficult for the NEIS to identify the fault that was affected.
> >
> > Their explanation of the quake makes less sense than ever;  there are no
> > faults in the area where sections of crust move longitudinally along a
> fault
> > and thrust upward.    The thrust upward part and the move longitudinally
> > part are the work of different faults.   Conceivably a piece of land
could
> > have moved upward if a new fault were created and a piece of land that
had
> > been held down bounced up, but again NEIS's explanation does not say
that
> > happened.
> >
> > Certainly if they could tell us so much as they did they ought to be
able
> to
> > identify the fault - particularly if it is a preexisting fault 600 miles
> > long.    Only one fault on Natawidjaja's chart appears to be a
candidate.
> > That would be the West Andaman fault.   The chart does not show whether
> the
> > West Andaman fault is 600 miles or more long; but it is the only fault
> that
> > exists in the area wehre the epicenter of the quake was, that extends
off
> of
> > the northern edge of the chart, and its name suggests that it must
extend
> > for some distance in the Andaman Sea.   There is also something funny
> about
> > how Natawidjaja has it labelled.  What is a nomocline fault?   He also
ahs
> > syncline faults and anticline faults, those terms refer to two sides of
a
> > hill in a folded area; does a nomocline fault also have something to do
> with
> > moving up and down?
> >
> > Yours,
> > Dora Smith
> > Austin, Texas
> > villandra@austin.rr.com
> >
>
>