From: Geoff 

To: psnlist 
Sent: Mon, 31 Dec 2012 10:56
Subject: Re: Omnidirectional instrument


I'm just interested in first time of arrivalas well as distance and depth b=
ut=20
not so muchabout axis. Possibly magnitude.=20
I think the plane of arrivalcan be extracted from three or more sites with
timing which is both accurate and precise.
At least GPS quality.

Hi Goeff,=20

    You don't need GPS quality timing. And a multitasking computer can't re=
cord it to=20
anything like the accuracy of the received signal. They run on an interrupt=
 cycling=20
system several hundred times a second.
    P waves usually have a velocity of 6 to 8 km / sec depending on depth, =
so if you=20
know the time correct to the nearest 1/10 of a second, this is good enough =
for our type=20
of seismology. You can get this easily from WWVB signals - but NOT over the=
 Internet.=20

    Regards,

    Chris Chapman
     =20
   =20


=20
From: Geoff <gmvoeth@hot=
mail.com>



To: psnlist <psnlist@..............>


Sent: Mon, 31 Dec 2012 10:56


Subject: Re: Omnidirectional instrument















I'm just interested in first time of arrivalas well as =
distance and depth but 

not so muchabout axis. Possibly magnitude. 

I think the plane of arrivalcan be extracted from three or more sites with
timing which is both accurate and precise.
At least GPS quality.

Hi Goeff, 



    You don't need GPS quality timing. And a multitasking computer can't record it to 

anything like the accuracy of the =
received signal. They run on an interrupt cycling 

system several hundred times a second.

    P waves usually have a velocity of 6 to 8 km / sec dep=
ending on depth, so if you 

know the time correct to the nearest 1/10 of a second, this is good enough =
for our type 

of seismology. You can get this easily from WWVB signals - but NOT over the Internet. 



    Regards,



    Chris Chapman