Re: Sumatra 100 foot shift

From: Alan Browne (alan.browne_at_FreeLunchVideotron.ca)
Date: 12/30/04 

Date: Thu, 30 Dec 2004 10:45:22 -0500

Stichting ST wrote:

> On Wed, 29 Dec 2004 19:35:50 -0500, Alan Browne
> <alan.browne@FreeLunchVideotron.ca> wrote:
>
>
>>Viper wrote:
>>
>>
>>>Thanks for that link Alan.
>>>While I don't think a tectonic 100 foot shift is unresonable in a major
>>>quake, (I live in Alaska, and I'm well aware of the potential Geo
>>>shifts from a quake) I still wonder what USGS was looking at that led
>>>them to the conclusion (even if "premature") that there had been one,
>>>and to what magnatude, and in what direction .....??(including vertical
>>>shifts)
>>>Satelite photos? GPS stations?
>>>
>>>I see that CNN now reports the planet's revolutions may have
>>>accelerated as a result of the quake.
>>>
>>>http://www.cnn.com/2004/TECH/science/12/29/quake.wobble.reut/index.html
>>
>>If somwbody said an island a km across moved 100 feet, I wouldn't blink. But a
>>1500 km long island moving that far without causing more earthquakes and
>>tsunamis on the other side as well (Singapore would have been badly hit, as well
>>as Borneo, Java, Vietnam, Cambodia, possibly Bankok, ... more).
>>
>>Even there they state that a GPS won't notice it... but surely a properly
>>instrumented system must. Of course it depends on what you compare it to (what
>>is the reference? Stars are usually the best). Per that article, enough mass
>>'dropped' to increase the spin rate (like a skater spinning and pulling in her
>>arms). 1,000,000 / 365 =~ 2740 years until a another leap second is needed due
>>to this event but an upheaval of similar mass at about the same latitude will
>>return it to the pre-earthquake rate. The earth is accelerating/decelerating
>>its spin all the time...
>>
>>Cheers,
>>Alan.
>
>
> well since 1964 they have measured the changes the big earthquake (also with
> tsunami) in Alaska made. See:
> http://www.drgeorgepc.com/Earthquake1964Alaska.html
> It states there:
> "The earthquake caused vertical displacements which ranged from about 15
> meters of uplift to 2.3 meters of subsidence relative to sea level."
> "According to field measurements conducted by the U.S. Geological Survey, the
> earthquake was accompanied by vertical displacements over an area of about
> 520,00 square kilometers. " (= 520,000?)
> "The zone of subsidence covered about approximately 285,000 square kilometers.
> It included the the west part of the Chugach Mountains, the north and west
> parts of Prince William Sound, most of Kenai Peninsula, and almost all the
> Kodiak Island group, all the way to Trinity islands."

I'm not surprised by vertical movement. After all the plates are literally
floating and there is nothing to resist them vertically other than gravity and
air. Horizontal movement is something else as there are other objects in the
way (you don't dig a hole in the ground by pushing the ground aside, you dig it
by pulling the ground out to make the hole, IOW.)

>
> So much for the vertical. For the horizontal I cannot find the amount of
> movement at the moment. But from the Alaska Denali Earthquake event (November
> 3, 2002):
> "Early reports of fault movements indicate that Sunday's event caused more
> than 18 feet of slip at the ground surface (and possibly much more) along at
> least a 150 mile-long stretch of the fault. Movement on the fault caused
> ground north of the fault to move eastward, relative to ground south of the
> fault."
>
> So 30 meters for a 1500 km long island seem much but it is not in the realm of
> the impossible.

Had it moved, then there would have been effects, as I say above, on the other
side... that's all I was saying.

Cheers,
Alan. 

-- 
-- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm
--        r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm
--      [SI] gallery & rulz: http://www.pbase.com/shootin
--                   e-meil: there's no such thing as a FreeLunch.

Relevant Pages

  • Re: Sumatra 100 foot shift
    ... >> quake, (I live in Alaska, and I'm well aware of the potential Geo ... >If somwbody said an island a km across moved 100 feet, ... "The earthquake caused vertical displacements which ranged from about 15 ... "Early reports of fault movements indicate that Sunday's event caused more ...
    (sci.geo.satellite-nav)
  • Re: Techtonics of Sumatra Earthquake
    ... about his own comments on some sort of discontinuity in the fault system in ... northern Sumatra, his answer was pretty much that I really need to read the ... the text describes the IFZ as having ... > That "barrier" can be seen in Figure 2.4, just south of Batu Island, ...
    (sci.geo.geology)
  • Re: So long, Gilligan
    ... It was the Professor's fault: if they'd got off the island sooner, ... Gilligan's health would have been better. ... Rob ...
    (misc.writing)
  • HAARP Cannot ?
    ... into the earth, and the island of Atlantis, in like manner disappeared ... the earth to locate underground munitions, ... the chief White House advisor on weather ... of the earthquake on February 28. ...
    (sci.physics)
  • Re: Sumatra 100 foot shift
    ... > the shft has had a measurable impact on the earth's revolutions. ... Sumatra is a huge island. ... Indonesian earthquake —An article in Monday's Section A said that Sunday's ...
    (sci.geo.satellite-nav)