On 4/28/12 3:32 PM, Tom Van Baak wrote:
Related to that, are there any seismometer experts on the list? I've
always wondered why they don't augment the extremely sensitive
detectors with less sensitive detectors? Of course a really good
detector will overload; so just co-locate cheap detectors that are 40
and 80 dB less sensitive. That way you get a clean signal no matter
how close or far the epicenter is from the detector.
here in southern California they have what they call "strong motion"
stations which are exactly what you describe. (and probably other
places, I just happen to know about the one that is co-located with a
regular station near where I live, because you can see the data online).
A lot of these are colocated with SCIGN stations (which have geodetic
quality GPS stations).
The sensors have maximums of several G as I recall. I think the peak
accelerations in 94 were around 1 G or a bit over. That is, stuff, like
houses, literally got launched into the air, as opposed to just shaken
til collapse. And of course, structural resonance effects amplify it
substantially.
There was a bigger push to get them going after Loma Prieta and Jan 94
Northridge, as I recall, because structure and other damage had "hot
spots" (due to various propagation effects across the santa monica
mountains, for instance), and they wanted better knowledge in a (certain
to occur) future event.
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