In a message dated 2007/08/09, gmvoeth@........... writes:

> It seems unlikely to me that an amatur has the abilities to build 
> scientific equipment with the abilities to properly recreate the actual ground motion.

Hi Geoff,

       Why do you say that? A long period Lehman has a ~flat response out to 
the edge of the band. The delays due to filters are often ~0.1 sec, maybe a 
bit more. You tend to get larger delays if you filter below 3Hz

> There are phase relationships involved that are\very difficult to
> properly record after passing through complex filter circuits.


       It largely depends on what filter circuits you use. The Butterworth 
filters have a sharp phase peak at the band edge. The Bessel filters show a slow 
change.

> The best we can hope to achieve are things like
> first time of arrival and relative energy content.

       The broad band filters are quite well compensated.

       You can compensate for time delays in WinQuake.

       Regards,

       Chris Chapman   
In a message dated 2007/08/09, gmvoeth@........... writes=
:



It seems unlikely to me that an=
 amatur has the abilities to build scientific equipment with the abilities t=
o properly recreate the actual ground motion.




Hi Geoff,



       Why do you say that? A long period Lehm=
an has a ~flat response out to the edge of the band. The delays due to filte=
rs are often ~0.1 sec, maybe a bit more. You tend to get larger delays if yo=
u filter below 3Hz



There are phase relationships i=
nvolved that are\very difficult to

properly record after passing through complex filter circuits.





       It largely depends on what filter circ=
uits you use. The Butterworth filters have a sharp phase peak at the band ed=
ge. The Bessel filters show a slow change.



The best we can hope to achieve=
 are things like

first time of arrival and relative energy content.




       The broad band filters are quite well c=
ompensated.



       You can compensate for time delays in W=
inQuake.



       Regards,



       Chris Chapman