PSN-L Email List Message

Subject: Re: digital filtering
From: Mark Robinson mark.robinson@...............
Date: Fri, 03 Feb 2006 11:48:19 +1300

Jón Frímann wrote:
> I have set the raw data on digital filtering, but that one is on 5.5Hz
> but the online graphs are now on 4Hz. It appears that the noise is
> somewhat above 10Hz (there is noise on 10Hz, but alot less then if i
> record from 2Hz to 60Hz), maybe above 6Hz.  I just haven tested it
> properly yet. I do not know how this filtering will effect my abliti to
> detect earthquakes. But i hope that the won't be any effect of this in
> regarding detecing earthquakes.

The more you filter the higher frequencies out the less small local events you 
will see.

If you look at and you will 
see that the first one shows local events while the second shows teleseisms. 
Both traces come from the same sensor, the Geonet display showing the data with 
all the long period stuff filtered out and the usgs one showing the same data 
with all the high frequencies filtered out.


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