PSN-L Email List Message

Subject: RE: Period
From: "Bob Hancock" carpediem1@.........
Date: Tue, 3 Jul 2007 07:03:52 -0700

Hi Geoff -

If you did sum all the channels, how would you compensate for the fact that
the P & S body waves do not always have the same initial direction
(compression or dilation,) of travel on all channels.  

In addition, how would you compensate for Love waves which only appear on
the transverse channel, and Rayleigh wave only appears only on the vertical
and radial channels?

Finally, the fault dynamics (focal mechanism) adds it own twist to the
amplitudes of waves and how visible they will be depending upon the event to
station and station to event azimuths.  

It would take a very complex algorithm to accomplish this and while I am
certain it could be done, I am not sure just what would be accomplished.


-----Original Message-----
From: psn-l-request@.............. [mailto:psn-l-request@............... On
Behalf Of Geoffrey
Sent: Tuesday, July 03, 2007 02:18
To: psn-l@..............
Subject: Re: Period

Hello tchannel1,

I think it might be interesting to sum all three axis
possibly by some kind of vector math to
obtain a single signal.
I have never done this before but I know
for a fact the main signal most probably is not
in any of the three planes but some vector of all
three together.


----- Original Message ----- 
Sent: Saturday, June 30, 2007 06:07
Subject: Period

Hi All,  I just did a side by side comparison of an Earthquake recorded by a
Vertical with a 2? second period and a Horz Pendulum 
with a 10? second period.  The different on this 6.7M at 10000km was very
pronounced, showing all the advantages of the Horz.

However, using the Vertical, I record many more Earthquake, and smaller
ones.  If the event is large, both sensors are impressive 
(to me).

In planning my next sensor, I need to pick a target period.   I already see
the advantage of each.  What period might be the best 
target?   Or is it just better to pick one end of the spectrum and not the

Thanks, Ted 


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