In a message dated 24/06/03, richard@............... writes:

>  I'm starting to set something up at home. I thought I'd first look for 
> local events and so purchased a few Geosource MD-100 geophones. They are labeled 
> 14Hz, 330 Ohms.
> Looking at pictures, I've seen similar units arranged in a cluster in a 
> X-Y-Z configuration. The MD-100s I have only work in one axis. Are there other 
> available (in the $20 range) units which work on their sides?
> The second question, which really should of been first, is: are these
> geophones adequate or appropriate for monitoring local events?

Hi Richard,

       The problem is not that local events don't generate vibrations that a 
14 Hz geophone can't pick up, but that the environmental / man made noise 
background is usually so large by 20 Hz and up. Sorry, but you are more likely to 
be monitoring road traffic with these units. 
       Call up http://www.seismicnet.com/ and read the notes under Used 
Geophones for Sale ---> Geophones and Earthquakes . Larry has 4.5 Hz L15B triaxial 
units for sale which might better fit your needs and your pocket.
       The L15Bs can have an additional output amplifier added later, to 
boost the response down to about 0.5 Hz, making them more useful for both local 
and regional events. (A bit like a powerful bass boost on your Hi-Fi.) Tele 
seisms need a response down to ~ 0.5 Hz.
       I suggest that you download Manual of Seismological Observatory 
Practice Also have a look at SCEC Education Module on Earthquakes at 
http://www.scecdc.scec.org/Module/index.html This has interactive programs to teach you about 
earthquakes.

       Regards,

       Chris Chapman
In a message dated 24/06/=
03, richard@............... writes:



 I'm starting to set someth=
ing up at home. I thought I'd first look for local events and so purchased a=
 few Geosource MD-100 geophones. They are labeled 14Hz, 330 Ohms.

Looking at pictures, I've seen similar units arranged in a cluster in a=20=
X-Y-Z configuration. The MD-100s I have only work in one axis. Are there oth=
er available (in the $20 range) units which work on their sides?

The second question, which really should of been first, is: are these

geophones adequate or appropriate for monitoring local events?



Hi Richard,



       The problem is not that local event=
s don't generate vibrations that a 14 Hz geophone can't pick up, but that th=
e environmental / man made noise background is usually so large by 20 Hz and=
 up. Sorry, but you are more likely to be monitoring road traffic with these=
 units.=20

       Call up http://www.seismicnet.com/=20=
and read the notes under Used Geophones for Sale ---> Geophones and Earthquakes . Larry has=20=
4.5 Hz L15B triaxial units for sale which might better fit your needs and yo=
ur pocket.

       The L15Bs can have an additional ou=
tput amplifier added later, to boost the response down to about 0.5 Hz, maki=
ng them more useful for both local and regional events. (A bit like a powerf=
ul bass boost on your Hi-Fi.) Tele seisms need a response down to ~ 0.5 Hz.

       I suggest that you download Manual of Seismological Obs=
ervatory Practice Also have a look at SCEC Education Module on Earthquak=
es at http://www.sc=
ecdc.scec.org/Module/index.html This has interactive programs to teach y=
ou about earthquakes.



       Regards,



       Chris Chapman