George,

The focal mechanism (one on the links on the page given below) indicates
strike slip faulting.
http://gldss7.cr.usgs.gov/neis/FM/Q0006181444.html

If the fault is oriented NS, parallel to the ridges seen in
the ocean-bottom topography, then the event was left lateral strike slip.

Maybe subduction into the trench to the northeast is faster/easier than the
northward motion of the Indian plate in the collision zone of the Himalayas.
This would then be a mirror image of the 7.6 right
lateral strike slip events in the Gulf of Alaska in 1987 and 1988.
http://quake.wr.usgs.gov/hazprep/alaska/AK_EQ_map_big.gif

John


At 01:43 PM 6/18/00 , you wrote:
>At 10:25 AM 6/18/00 -0700, you wrote:
> >The NEIC reports it as the; south Indian Ocean, and believed
> >to be the largest known earthquake for the area.  Mw 7.5  See:
> >
> >http://gldss7.cr.usgs.gov/neis/bulletin/000618144413.HTML
> >
>Meredith-
>
>         The location of this quake is very interesting. I looked at the 
> history
>display and noticed very few previous quakes in the area. The shallow
>ridges on the ocean floor look sort of like spreading ridges. I didn't
>think that spreading centers caused large earthquakes such as this. I
>wonder if we are seeing the start of a volcano?
>
>George Bush
>Sea Ranch, CA, USA
>38.74N, 123.5W
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John C. Lahr
1925 Foothills Road
Golden, CO 80402
(303) 215-9913
john@........
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