[time-nuts] GPS, USGS Early Earthquake Warning

[Tom Van Baak]

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