PSN-L Email List Message
Subject: Caution on low pass filtering emphasis
From: RSparks rsparks@..........
Date: Wed, 30 Dec 2009 12:45:09 -0800
I sometimes think that we amateur seismologist over-emphasize the need
for low pass filtering, with the unexpected result that we destroy the
fidelity of the earthquake signal. To illustrate what we might be
losing, I posted my recording of this mornings Baja quake using both raw
data and HIGH PASS filtered data in the WinQuake volume format. The
high pass was done using WinQuake filters set at 1 Hz, two pole.
Here is a link to the posting:
The trace on the bottom is the raw data.
As you can see, the quake was about 1677 km from this station but there
was still lots of high frequency (> 1 Hz) in the data. If filtered low
pass below 1 Hz, this information would be compromised, and as you can
see, there is a lot of information to be lost.
Something to think about,
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