If you look at  my force balance  instrument traces on the PSN current =
seismicity web site you will see long period signals in the few hours =
after the event. Theses are the whole earth or earth normal modes which =
were excited by the event.

The instrument long period corner is 50 seconds and the motion is at =
significantly longer periods but the motion is so  large the instrument =
response is sufficient to provide a nice display.  My Trillium Compact =
with its 120 second corner is much better but it is not an amateur class =
instrument.=20

I have made a spectrum in Winquake and the individual modes are quite =
apparent and individually identifiable.






If you look at  my force =
balance =20
instrument traces on the PSN current seismicity web site you will see =
long=20
period signals in the few hours after the event. Theses are the whole =
earth or=20
earth normal modes which were excited by the event.
 
The instrument long period corner is 50 =
seconds and=20
the motion is at significantly longer periods but the motion is so=20
 large the instrument response is sufficient to provide a nice=20
display.  My Trillium Compact with its 120 second corner is much =
better but=20
it is not an amateur class instrument. 
 
I have made a spectrum in Winquake and =
the=20
individual modes are quite apparent and individually =
identifiable.
 
Interesting stuff=20
!!