PSN-L Email List Message
Subject: Short period vs Long period
From: tchannel1@............
Date: Wed, 5 Mar 2008 15:07:53 -0700
Hi All, Perhaps someone can explain the different in recorded data, =
between a (let's say a Lehman) at 2 second period and the same sensor at =
20 seconds.
I have compared data from two such sensors. Here is what I have found, =
but I am sure I am understanding the TRUE difference.
I get smaller EQ's on the shorter periods, my guess is about 1/3 more =
events. Mainly on the closer EQ's or smaller EQ's for the 2 second =
machine.
That is not to say the 20 second period machine, does not pick these up, =
just not as many, if they are weak. =20
If it is a big event I get it on both machines equally? If it is a =
medium event I get it on both machines. But, if it is weak, definitely =
better on the 2 second machine.=20
About the only difference, I can see on the 20 second machine traces is =
the duration. On a 8.0M the 20 second trace could be three hours long =
on the 2 second machine maybe only one hour.
I do understand the teleseismic, traveling greater distances, loses the =
higher frequencies, and those remaining can be in the range of 10-20 =
seconds.
However I pick up the teleseismic very well on the 2 second machine, =
they are just not as long in duration.
Hi All, Perhaps someone can =
explain the=20
different in recorded data, between a (let's say a Lehman) at 2 second =
period=20
and the same sensor at 20 seconds.
I have compared data from two such=20
sensors. Here is what I have found, but I am sure I am =
understanding=20
the TRUE difference.
I get smaller EQ's on the shorter =
periods, my=20
guess is about 1/3 more events. Mainly on the closer EQ's or =
smaller=20
EQ's for the 2 second machine.
That is not to say the 20 second period =
machine,=20
does not pick these up, just not as many, if they are weak. =20
If it is a big event I get it on both =
machines=20
equally? If it is a medium event I get it on both =
machines. =20
But, if it is weak, definitely better on the 2 second machine. =
About the only difference, I can =
see on the 20=20
second machine traces is the duration. On a 8.0M the 20 =
second trace=20
could be three hours long on the 2 second machine maybe only one=20
hour.
I do understand the teleseismic, =
traveling greater=20
distances, loses the higher frequencies, and those remaining can be =
in the=20
range of 10-20 seconds.
However I pick up the teleseismic very =
well on the=20
2 second machine, they are just not as long in =
duration.
Thanks, Ted
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