[Beowulf] Re: Disks fail at what acceleration? (Jim Lux)

[Karen Shaeffer]

On Thu, Mar 23, 2006 at 11:54:49AM -0500, Robert G. Brown wrote:
> On Thu, 23 Mar 2006, David Mathog wrote:
> 
> >Jim Lux wrote
> >
> >>At 01:24 PM 3/22/2006, David Mathog wrote:

> There is actually a bunch of data
> out there on retrospective analyses of e.g. some relatively famous
> failures of raised floor and other infrastructure in some of the
> semi-major earthquakes of the last decade and a half, where some designs
> that were supposed to work did not and others that weren't really
> designed for it did OK.
> 
> Remember, it isn't just "g forces" -- earthquakes cause the ground to
> vibrate. 

Hi Robert,

I was in Moffet Park in Sunnyvale for the 1989 Loma Prieta (7.2) quake.
>From that experience, I can say that really large earthquakes do create
a lot of very chaotic motion. There were very strong vibrations. I remember
running for a door, and seeing that door vibrating violently as I tried to
open it. And the motions can be in any direction as well. In that
earthquake, Silicon Valley is ringed by mountains, and the shock waves were
bouncing off the mountains and returning for another ride. All told we were
shaking violently for about 45 seconds. And that is a lot longer than it
sounds, when all hell has broken loose. Loma Prieta was mostly horizontal
shaking, while Northridge included a lot of vertical movement. You can
shake in any direction during a large earthquake.

Designing a system to survive a large earth quake with a high probability
would likely be very costly.

I'll tell you, the most interesting part of my Loma Prieta experience was
the beginning. You could hear the roar of the earth moving about 1 or 2
seconds before the shaking started. It was an indescribable roar. It was
as loud as thunder and just kept getting louder. And then, once the shaking
started, the building was making incredible noises, as it struggled against
the force of movements. And then I saw that door vibrating violently, and
I knew this was a really major event. Very very scary.

OK, back to work.
Karen
-- 
 Karen Shaeffer
 Neuralscape, Palo Alto, Ca. 94306
 shaeffer at neuralscape.com  http://www.neuralscape.com