Re: Japanese papers reveal huge quake

In article <[EMAIL PROTECTED]>,
 Damon Hill <[EMAIL PROTECTED]> wrote:

> Gerard Fryer <[EMAIL PROTECTED]> wrote in
> news:[EMAIL PROTECTED]: 
>  
> > What is new is the additional analysis. The BBC picked up on the
> > latest issue of JGR (probably prompted by a press release) which has
> > an article by Satake, Kelin Wang, and Brian Atwater. The paper is an
> > attempt to work out rupture dimensions and moment, guided by the
> > shoreline geological evidence (Atwater), the GPS and plate locking
> > evidence (Wang), and computer modeling (Satake).
> > 
> > True, the determination that there was a giant earthquake on Jan 26
> > 1700 is not news, but there were plenty of sceptics (including me)
> > waiting for stronger evidence. The new compilation further justifies
> > the giant earthquake hypothesis, and imposes valuable constraints on
> > what the event was really like. This follow-up work was essential, and
> > this paper will not be the end of it--the earthquake hazard assessment
> > for the Pacific Northwest deserves no less.
> 
> Being a resident of the PNW (between Seattle and Tacoma), I'd
> be interested in an analysis of how that same earthquake would
> have affected the inland region, considering that it was two
> orders of magnitude stronger than our M6.8 of a couple of years ago.
> 
> Granted, it was out in the Pacific and likely deep, but I suspect it
> might have done more than slosh Puget Sound into downtown Seattle.

The tsunami threat to Seattle from such events is likely small, since 
the tsunami would not be generated directly in Puget Sound and instead 
would have to thread its way in from the ocean. More serious would be 
the shaking. The severity of shaking would probably be similar to what 
you felt in the M6.8 event, but it would last far longer, perhaps five 
minutes. While that might not be devastating, damage would be very 
widespread. Make sure your house is bolted to the ground!

BTW, the 1700 event had to be shallow, since it created a large tsunami.

Despite the widespread damage to be expected from a monster subduction 
earthquake along the Cascadia margin, a greater threat to Seattle has to 
be the Seattle Fault.