## PSN-L Email List Message

Subject: Re: Time of Quake??
From: "tchannel" tchannel@..............
Date: Sat, 21 Apr 2007 11:53:51 -0600

```Hi Chris, A question about P travel time?  I read somewhere it varies, =
from __km to __km per second.
Does it vary depending on the material, type of earth, that it is moving =
through?
I have calculated, from recordings, a range of 10,000 to 30,000 miles =
per hour. That's a big range.

I would like to have a better understanding of it.   Thanks, Ted
----- Original Message -----=20
From: ChrisAtUpw@..........
To: psn-l@.................
Sent: Saturday, April 21, 2007 9:34 AM
Subject: Re: Time of Quake??

In a message dated 2007/04/21, Paulc@........ writes:

=20
For the past month I have been working on a horizontal pendulum =
sensor and I am going through my maiden voyage with it.
The clock is accurate to within 10 seconds, I am using the =
Amaseis program, and a 12 bit ADC.

Hi Paul,

The P waves may travel at 8.2 km / sec. You need your clock =
accurate to about 1 sec for practical purposes. I suggest that you keep =
a note of the errors for a day or two. They are often very large.
You can buy a radio corrected crystal clock for less than \$20. =
They are very useful and are accurate to 20 mS. They update every hour.=20
You can also visit http://nist.time.gov/ and cross check =
on-line, but do watch out for transient data delays.

I would like to try and compare events elsewhere in the world / =
country to my sensor. At this site I can see various locations.

The question.

If I know in  when in UTC an event occurred, and where.. how do =
I convert that to a UTC time when the event would arrive at my location, =
if ever.
In other words how ho long does it take to get here??

Y
ou can calculate arrival time using =
http://neic.usgs.gov/neis/travel_times/=20

from the P to S delay time.

Regards,

Chris Chapman

Hi Chris, A question about P travel =
time?  I=20
read somewhere it varies, from __km to __km per second.
Does it vary depending on the material, =
type of=20
earth, that it is moving through?
I have calculated, from recordings, a =
range of=20
10,000 to 30,000 miles per hour. That's a big range.

I would like to have a better =
understanding of=20
it.   Thanks, Ted

----- Original Message -----
From:=20
ChrisAtUpw@.......
To: psn-l@..............
Sent: Saturday, April 21, 2007 =
9:34=20
AM
Subject: Re: Time of =
Quake??
In a=20
message dated 2007/04/21, Paulc@........=20
writes:
For the past month I have been working on a horizontal =
pendulum=20
sensor and I am going through my maiden voyage with it.    The clock=20
is accurate to within 10 seconds, I am using the Amaseis program, =
and a 12=20
Paul,       The P waves may =
travel at=20
8.2 km / sec. You need your clock accurate to about 1 sec for =
practical=20
purposes. I suggest that you keep a note of the errors for a day or =
two. They=20
are often very large.       You can =
radio corrected crystal clock for less than \$20. They are very useful =
and are=20
accurate to 20 mS. They update every hour.=20
You can also visit=20
http://nist.time.gov/ and cross check on-line, but do watch out for =
transient=20
data delays.
I would like to =
try and=20
compare events elsewhere in the world / country to my sensor. At =
this site I=20
can see various locations.The =
question.    If I know=20
in  when in UTC an event occurred, and where.. how do I convert =
that to=20
a UTC time when the event would arrive at my location, if =
ever.In other words =
how ho long=20
does it take to get here??   Y
ou can calculate arrival time using http://neic.usgs.gov/nei=
s/travel_times/=20
=20
and also =
and charts to measure the distance from the P to S delay=20
time.      =20
Regards,       Chris =
Chapman
```