Hi Geoff -

Use the following link to a USGS program and add the appropriate  
information:

	http://neic.usgs.gov/neis/travel_times/compute_tt.html

The answer you are looking for will be near the top of the page, prior  
to the listing of the arrival times of the phases.

Cheers

Bob Hancock


On Oct 18, 2008, at 11:01 PM, Geoff wrote:

> Gee Whillikers Guys, my system is only designed to get
> 2Hz to 3 Second vertical (Z) waves but with this Tonga quake
> a few minutes ago Im getting 20 second surface waves
> they must be really large since my system is relatively
> insensitive at these periods. Can someone give me an
> idea of the actual peak ground deflection from this
> 7.1 Tonga Quake at 20 seconds period surface waves and 81 degrees  
> away ?
> I do not know how to do this myself.
> regards
> geoff
>
>
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