PSN-L Email List Message

Subject: Re: Time of Quake??
From: ChrisAtUpw@.......
Date: Sat, 21 Apr 2007 11:34:35 EDT

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

> 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.
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/
>
and also download tables and charts to measure the distance from the P
to S delay time.

Regards,

Chris Chapman

In a me=
ssage dated 2007/04/21, Paulc@........ writes:

For the=20=
past month I have been working on a horizontal pendulum sensor and I am goin=
g through my maiden voyage with it.
The clock is accurate to within 10 seconds, I am using t=
he 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 sugge=
st that you keep a note of the errors for a day or two. They are often very=20=
large.
lock for less than \$20. They are very useful and are accurate to 20 mS. They=
update every hour.
You can also visit http://nist.time.gov=
/ and cross check on-line, but do watch out for transient data delays.

I would lik=
e to try and compare events elsewhere in the world / country to my sensor. A=
t this site I can see various locations.

The question.

If I know in  when in UTC an event occurred, and wh=
ere.. how do I convert that to a UTC time when the event would arrive at my=20=
location, if ever.
In other words how ho long does it take to get here??

You can calculat=
e arrival time using htt=
p://neic.usgs.gov/neis/travel_times/