[time-nuts] GPS, USGS Early Earthquake Warning

Brooke Clarke brooke at pacific.net
Sat Apr 28 21:49:59 UTC 2012


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
http://www.PRC68.com
http://www.end2partygovernment.com/Clarke4Congress.html


Tom Van Baak wrote:
> Brooke,
>
> In the papers they were getting some results with even 1 Hz sampling,
> but, as expected, 10 Hz was better. That's probably sufficient for seismic
> waves; 100 Hz is overkill. See Figure 5 of the Larson paper I for a nice
> example of the AC vs. DC coupling that you mentioned.
>
> I also agree with Jim's earlier comment; for earthquake detection it
> seems an cheap accelerometer is more than adequate. One doesn't
> need the expense of dual frequency carrier phase gps receivers just
> to detect a local shake.
>
> These days, there are always many cell sites where there are many
> people; and each site already has GPS timing, battery backup, and
> a fast connection to a central office; so it's the perfect place to add
> a sensitive accelerometer. You could just call it an security intrusion
> monitor and use it for earthquake detection as a free side effect.
>
> /tvb
>
>> Hi Hal:
>>
>> In the talk there was a slide showing a comparison between ground position calculated from an accelerometer and a 
>> real time precision GPS.
>> The Accelerometer is AC coupled and so misses the DC coupled GPS answer that shows the permanent ground movement.
>> I'm guessing it takes a GPS receiver that has 100 Hz or faster outputs that can be reduced to cm or better position 
>> to do this.
>>
>> Have Fun,
>>
>> Brooke Clarke
>
>
>
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