[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: looking for clear explanation of the earthquake



--- Dora Smith <villandra@austin.rr.com> wrote:

> Say, I bet there are people on this list who are
> qualified to explain this.
> Or maybe could tell me where to go to get an actual
> clear logical
> explanation.  There are specialists in Southeast
> Asian plate tectonics at UT
> Austin but they are on vacation and I can't reach
> them.
> 
> First of all, what are teh Burma and Sunda plates -
> besides part of the
> Eurasian Plate?

Southeast Asia is considered by many authors to be
moving independently of Eurasia, and it is called by
some as the Sunda Block (The plate encompasses
everything on the Sunda shelf, or Sundaland).It is
"assumed" to be relatively stable in recent times,
hence considering it as a single, rigid plate. During
the Cenozoic, there was much more tectonic activity,
with multiple changes in plate boundaries, including
the separation forming the Burma block.

You should try Hall (2002) for references

Hall, R. (2002). Cenozoic geological and Plate
Tectonic Evolution of SE Asia and the SW Pacific:
Computer Based Reconstructions, Models and Animations.
Journal of Asian Earth Sciences 20(4): 431p.

And yes, definitely Dilong.

Meor,
University of Malaya

--- Dora Smith <villandra@austin.rr.com> wrote:

> Say, I bet there are people on this list who are
> qualified to explain this.
> Or maybe could tell me where to go to get an actual
> clear logical
> explanation.  There are specialists in Southeast
> Asian plate tectonics at UT
> Austin but they are on vacation and I can't reach
> them.
> 
> First of all, what are teh Burma and Sunda plates -
> besides part of the
> Eurasian Plate?
> 
> Is the Burma "microplate" actually just a zone of
> loose rock and faults?
> It appears to constitute the entire region
> immediately east of the java/
> sunda trench, which is the point where the
> Australian and Indian plates
> (which of those plates is actually there and whether
> they are two plates is
> clearly a matter of controversy) slides under the
> Eurasian plate.   Why is
> the Burma plate or microplate called a plate at all?
>    Logically it is a
> fault zone, probably uplifted above the trench.
> 
> On one of the faults in the area I found evidence
> that some rock tries to
> move out of the way, along the fault zone.   Is the
> Burma plate an area of
> crust that is behaving in this way?    That would
> logically account for
> NEIS's insistence that the India and Australia
> plates move northward as well
> as eastward with respect to it ( though it would
> require that the Burma
> plate in fact be moving south) - and that there are
> slip/ slide faults along
> the boundary.
> 
> WHAT exactly is the Sunda plate, and why is it
> called a separate plate?
> The Sunda plate is part of the Eurasian plate and
> not usually depicted as a
> separate plate.   In fact before last night I could
> find next to nothing
> about it in Google, except that two countries sit on
> it.    I have been
> unable to find a map that shows the entire Sunda
> plate, but it appears to
> constitute Burma, Thailand, and Vietnam, and the
> Indonesian islands to the
> north and east of the java trench/ island arc formed
> where the Australian
> and Indian plates meet the Eurasian Plate.    On the
> western border, it
> meets with the Pacific plate, and its rigidity
> relative to plates around it
> purportedly causes trouble for Bali and another
> nation that sits on its
> boundaries.
> 
> I didn't find anything that says it moves
> differently with respect to the
> rest of the Eurasian plate or something - which is
> the rationale for
> thinking there is an Indian plate separate from the
> Australian plate.    I
> found a whole article showing that those two paltes
> move differently with
> respect to each other though thye have a poorly
> defined border and noone can
> decide where it is.
> 
> Speaking of noone knowing where the boundary is
> between the India and
> Australia plates, where is it?   Before yesterday,
> the eastern border of teh
> India plate was I think the mid-ocean Ninety-east
> ridge.    Now suddenly the
> India and Australian plates have an east-west
> boundary that ends at the java
> / sunda trench off of northern Sumatra, near where
> the quake occurred - and
> that helped cause the earthquake.
> 
> Now the part I REALLY don't understand.   NEIS's
> explanation of how the
> quake happened - which I found more or less
> paraphrased elsewhere.    The
> India and Australia plates move northeast with
> respect to the Eurasia plate
> and subducts underneath it where the plates meet.  
> Logical so far.    Where
> this takes place there are thrust faults.   Also
> logical.   It more or less
> requires that parts of the Eurasia plate are thrust
> upward at the boundary.
> That in fact created the entire island arc.
> 
> Now for not logical.    According to NEIS, the India
> and Australian plates
> also move northeast with respect to the "Burma
> microplate", which makes
> slip/ slide faults like the San Andreas fault in
> California, where two
> plates glide sort of smoothly past each other.  
> Occasionally they hang up,
> and when the rock breaks there is a quake.  Then the
> two plates continue
> their seperate northward and southward journeys.  
> Quakes in California do
> not result in land near the fault thrusting upward.
> 
> According to NEIS, as paraphrased in various places
> with no other detailed
> explanation of the quake available, this quake
> resulted from a rock breaking
> loose along a SLIP/ SLIDE fault, between the India/
> Australia and Burma /
> Eurasia plates.    When that happened, a nine- mile
> wide strip along the
> entire near boundary of the Burma/ Eurasian plate,
> abruptly SLIPPED, and
> THRUST a hundred feet UPWARD.    That just doesn't
> sound like something a
> slip/slide fault could do.
> 
> How is this even possible?   Is what really happened
> that the Australia/
> India plate got stuck while sliding UNDER the Burma
> plate, and when it broke
> free the edge of the Burma plate abruptly thrust
> upward?     That would be
> far more logical.
> 
> By the way, is there ANY justification for thinking
> that New Zealand sits on
> its own plate?  Two plates meet and twist in a
> bizarre way there - hard to
> see how there could be a separate plate, nor how
> there would be just ONE
> separate plate, logic says there would have to be
> two;  but maybe it's a
> Burma microplate sort of thing?
> 
> By the way, the best single article I have seen on
> the quake by far is at
>
http://en.wikipedia.org/wiki/2004_Indian_Ocean_earthquake,
> and there are
> links to the main media web sites on the quake,
> which is more than google
> news has managed to do.
> 
> Yours,
> Dora Smith
> Austin, Texas
> villandra@austin.rr.com
> 
> 



                
__________________________________ 
Do you Yahoo!? 
The all-new My Yahoo! - Get yours free! 
http://my.yahoo.com