PSN-L Email List Message

Subject: Re: Time
From: Mauro Mariotti mariotti@.........
Date: Sat, 07 May 2005 09:20:15 +0200


this brings the need to apply to the recorded signal
a convolution algorythm in order to retrieve the exact
ground motion that will correct the waveform also in the
time domain and will put down to zero the filter delay
at various frequency.

Winquake should have the possibility to insert
(or better to pick from the file)
at least these parameters:

(Example for velocity sensors)
- Sensor damped sensitivity
- Resonance frequency of the sensor
- Filter corner frequency
- Filter type
- Number of Filter poles

If a convolution is made over the waveform the
original ground motion can be reconstrcuted.
This would be a great improvement of an already good
software as WinQuake is.


At 01:23 07/05/2005, you wrote:
>In a message dated 06/05/2005, lcochrane@.............. writes:
>With the Garmin GPS receiver your timing should be accurate to within one 
>or two
>Larry Cochrane
>Hi Larry,
>     Do you have any figures, or preferably measurements, for the time 
> delay produced by the filters on your amplifier boards, please?
>     Putting in the values for an 8th order 5 Hz Butterworth low pass 
> filter suggest that the delay is likely to be ~160 milli sec below 2 Hz, 
> peaking to about 280 milli sec at 5 Hz.
>     These delays, while swamping any timing errors, are unlikely to give 
> significant errors in general Earthquake location. However, since an 8 
> pole 1.5 Hz filter can produce a lag of over 1/2 second, we may sometimes 
> need to take filter delays into account, more particularly for local events.
>     Regards,
>     Chris Chapman


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