PSN-L Email List Message

Subject: RE: Time of Quake??
From: "Paul Cianciolo" Paulc@........
Date: Sat, 21 Apr 2007 14:54:40 -0400

Hey Guys,

Thanks for all the input on the time question.

First I did make a mistake, as Steven pointed out.  Thanks Steve...  Yup I
was adding the time..  Sorry for the dumb mistake.

I am going to check out the links that you folks pointed out.

I also have a 10 MHz GPS discipline standard... a Z3801  and will look into
interfacing that to my computer.

But will somebody please tell me why the clock accuracy is so important??
It appears that events last multiples of minutes and longer.  Why is clock
accuracy in milliseconds so important.
Unless one is trying to "triangulate" or compare phase of signals.. I must
be missing something.


-----Original Message-----
From: psn-l-request@..............
[mailto:psn-l-request@................. Behalf Of dave
Sent: Saturday, April 21, 2007 1:45 PM
To: psn-l@..............
Subject: Re: Time of Quake??


there is a program at
that keeps your computer within tenths of a second and is free.
if you have an always on connection it can update time as often
as you like.

once in awhile the program appears to not work and what i found is that
the server it is using to get the time has failed.  if you select another
server things will be ok.

short of using a gps disciplined clock this is probably the easy and is
accurate enough for us.

dave k7da

ChrisAtUpw@....... wrote:
> 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 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??
>    You can calculate arrival time using
>        and also download tables and charts to measure the distance from
> the P to S delay time.
>        Regards,
>        Chris Chapman

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