In the early 1980's I visited the dominion radio astronomy observatory in Canada. I observed a bunker like structure and asked my host what it contained, he advised me that it housed a special seismograph that would only be of use in the event of a large earth quake.
Sent from my iPod On 2012-04-28, at 3:53 PM, Brooke Clarke <[email protected]> wrote: > Hi Tom: > > They do use two different seismometers at each location, a large movement and > a sensitive. > http://www.prc68.com/I/Seismometer.shtml > > Have Fun, > > Brooke Clarke > http://www.PRC68.com > http://www.end2partygovernment.com/Clarke4Congress.html > > > Tom Van Baak wrote: >> Brooke, >> >> Right, an overloaded accelerometer is a problem -- if you have >> only one or a few of them. >> >> But the beauty of using cellular sites is that you have hundreds >> or thousands of them across populated areas; so it's no problem >> if the a bunch of sensors near the epicenter overload. A clipped >> signal is not worthless; at least you know something big happened >> there; you can rely on slightly more distant cell tower sensors to >> get readings a few seconds later that are less clipped or not clipped >> at all. (There's another solution I heard about -- using smartphones >> as a tiered network of synchronized accelerometers). >> >> A high rate GPS solution sounds really cool to me but I bet its also >> far more expensive. >> >> 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. >> >> /tvb >> >> ----- Original Message ----- From: "Brooke Clarke" <[email protected]> >> To: "Tom Van Baak" <[email protected]>; "Discussion of precise time and >> frequency measurement" <[email protected]> >> Sent: Saturday, April 28, 2012 2:49 PM >> Subject: Re: [time-nuts] GPS, USGS Early Earthquake Warning >> >> >>> Hi Tom: >>> >>> The USGS talk was the first time I'd heard about the need to look at an >>> earthquake as happening along some length of fault line. For the big quake >>> in Japan the forecast software assumed a point source for the quake and >>> that cause them to under estimate the magnitude and get other things wrong. >>> GPS is part of the solution to get better results. >>> >>> In the S. CA example he showed a 180 mile long rupture of the San Andreas >>> fault. At 2 miles a second the quake would last about 90 seconds. >>> Accelerometers that are not right on top of the fault will be overloaded >>> with signals coming from each location where there's a fracture and so the >>> data will be nearly impossible to untangle in a short time frame. But a >>> GPS receiver will show a DC displacement that unambiguous. >>> >>> Have Fun, >>> >>> Brooke Clarke >> >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
