Great, Great question! Since I have no idea and have wondered in the past..=
I'd =0Alove to see some answers!=0A=0A=0A=0A=0A____________________________=
____=0AFrom: Thomas Dick =0ATo: psnlist@seismic=
net.com=0ASent: Fri, October 15, 2010 10:32:41 AM=0ASubject: Period of seis=
mic units=0A=0AI asked Larry about this and he wanted me to post it here. I=
 think he was trying =0Ato get rid of me. It probably shows how little I kn=
ow and that I am missing =0Asomething. This question came out of the activi=
ty in the Guy area which is about =0A500 miles west of me as well as the Ne=
w Madrid system which is closer. It seems =0Athe records are better on the =
2-4 Hz units. Here was my question;=0A=0A> It is about this geophone vs leh=
man or other long period instruments. In=0A> California you have many local=
 quakes. These quakes have frequencies=0A> higher than long distance quakes=
.. What is the logic of (just/or popularity of) =0A>long=0A> period instrume=
nts out there? What precipitated this trend? The 1-5 Hz units =0A>should be=
 better on local events -- which you have a lot.=0AThere are many Californi=
a quakes and there is the activity in Washington State =0Aand Yellowstone b=
ut you never see local seismic detectors being posted with =0Aperiods of 1-=
4.5 Hz -- except possibly tchannel.=A0 Shouldn't these units help =0Adiffer=
entiate human noises like quarry activity from smaller local earthquake =0A=
activity?=0A=0A__________________________________________________________=
=0A=0APublic Seismic Network Mailing List (PSNLIST)=0A=0ATo leave this list=
 email PSNLIST-REQUEST@.............. with the body of the =0Amessage (firs=
t line only): unsubscribe=0ASee http://www.seismicnet.com/maillist.html for=
Great, Great question! Since I have no idea and have w=
ondered in the past..I'd love to see some answers!
=0A
=

=0A
=0A
=0AFrom: Thomas Dick <dickthomas01@..............
>
To: psnlist@seismic=
net.com
Sent: Fri, Octob=
er 15, 2010 10:32:41 AM
Subject: Period of seismic units

I asked Larry about this and=
 he wanted me to post it here. I think he was trying to get rid of me. It p=
robably shows how little I know and that I am missing something. This quest=
ion came out of the activity in the Guy area which is about 500 miles west =
of me as well as the New Madrid system which is closer. It seems the record=
s are better on the 2-4 Hz units. Here was my question;

> It is a=
bout this geophone vs lehman or other long period instruments. In
> C=
alifornia you have many local quakes. These quakes have frequencies
>=
 higher than long distance quakes. What is the logic of
 (just/or popularity of) long
> period instruments out there? What pr=
ecipitated this trend? The 1-5 Hz units should be better on local events --=
 which you have a lot.
There are many California quakes and there is the=
 activity in Washington State and Yellowstone but you never see local seism=
ic detectors being posted with periods of 1-4.5 Hz -- except possibly tchan=
nel.  Shouldn't these units help differentiate human noises like quarr=
y activity from smaller local earthquake activity?

_________________=
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ling List (PSNLIST)

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