In a message dated 24/01/2006, asc@............... writes:

Jon
I  have been enjoying this exchange of information. The frequency range of 
local  earthquakes in Iceland is typical of the frequency range of small 
earthquakes  recorded on rock near to the source. You just have to sample at a high 
rate  100 or preferably 200s/s to see it. For monitoring of mining rock bursts 
up  close you have to increase this rate by a factor of 10 or more.
In the  Lachlan Foldbelt in south-eastern Australia we typically record 
ground shaking  near 50 Hz for small earthquakes up to ML 4 and there isn't a 
recently active  volcano for 500 km or so.
Regards
Kevin



Hi Jon, Kevin,
 
    Jon is using one of Larrys's four channel amplifier  boards. These have a 
nominal bandwidth of 20 sec to 10 Hz, with an 8 pole  Butterworth roll off. 
It is 20 dB down by 20 Hz and 40 dB down by 30 Hz. I doubt  if there is any 
point in sampling beyond 50 sps, and 30 sps would probably  would be 
satisfactory. See _http://psn.quake.net/serialamp.html_ 
(http://psn.quake.net/serialamp.html) 
    Jon also has sea noise and local environmental  noise to cope with. 
    Your comments, please, Kevin?
 
    Regards,
 
    Chris Chapman






In a message dated 24/01/2006, asc@............... writes:
<=
FONT=20
  style=3D"BACKGROUND-COLOR: transparent" face=3DArial color=3D#000000 size=
=3D2>Jon
I=20
  have been enjoying this exchange of information. The frequency range of lo=
cal=20
  earthquakes in Iceland is typical of the frequency range of small earthqua=
kes=20
  recorded on rock near to the source. You just have to sample at a high rat=
e=20
  100 or preferably 200s/s to see it. For monitoring of mining rock bursts u=
p=20
  close you have to increase this rate by a factor of 10 or more.
In the=20
  Lachlan Foldbelt in south-eastern Australia we typically record ground sha=
king=20
  near 50 Hz for small earthquakes up to ML 4 and there isn't a recently act=
ive=20
  volcano for 500 km or so.
Regards
Kevin


Hi Jon, Kevin,
 
    Jon is using one of Larrys's four channel ampli=
fier=20
boards. These have a nominal bandwidth of 20 sec to 10 Hz, with an 8 pole=20
Butterworth roll off. It is 20 dB down by 20 Hz and 40 dB down by 30 Hz. I d=
oubt=20
if there is any point in sampling beyond 50 sps, and 30 sps would proba=
bly=20
would be satisfactory. See http://psn.quake.net/serialamp.=
html
    Jon also has sea noise and local environmental=20
noise to cope with. 
    Your comments, please, Kevin?
 
    Regards,
 
    Chris Chapman