PSN-L Email List Message

Subject: Re: New Station Questions
From: John & Jan johnjan@........
Date: Tue, 27 Aug 2002 09:30:13 -0600

Dear Jonathan,

It's great that you've set up a seismograph station in your 
school!!!  There is a
national effort to promote school-based seismic recording which is supported by
the NSF through IRIS 
 and the USESN
US Educational Seismograph Network .
Your efforts and feedback to these groups would be very helpful to the effort.

At 06:56 AM 8/27/2002 -0700, you wrote:
>So, onto the questions:
>1) What is the average sample rated used by stations?
This relates to the sensor period and the type of earthquake that one wants
to record.  For local events a sensor with a natural frequency of 1 to 2 Hz is
ideal and sample rates of  50 Hz to 100 Hz are typically used.  Keep in mind
that a filter is required prior to the AD that will eliminate frequencies above
the Nyquist frequency 

which is one half of the sampling frequency.

For recording distant (teleseismic) events a sensor with a period of about 
15 - 20
seconds is good because the surface waves have a lot of energy in this range.
Due to limited dynamic range the higher frequencies are often filtered out from
a long-period system, so a high cut filter might be set to 1 Hz and the 
rate set to 6 Hz.

>2) What level of compression is usually used to examine results?

I'm not sure what your question is.

>3) Where can I find information to determine an ideal or reasonable level of

Dampening is usually set to a bit less than critical.
For all the details, see: 
Roughly what you want when the pendulum is bumped is for it to
reach a peak, return past zero to another peak and then return to
zero with very little overshoot.

>4) How can I convert magnitude to UG or MM?

If you system is calibrated so that you know what the peak amplitude
is in microns for a local event, then you can use Richter's original
magnitude formula to estimate the magnitude.  See:

>5) Does anyone know of quakeware  that will work with this A/D board?
You could try the AmaSeis program written by Alan Jones.  It works
with the DI154RS Dataq AD but I'm not sure about the DI194RS unit.
See Alan web site for this an two other free programs for seismology

Best of luck with your seismology.

John C. Lahr
1925 Foothills Road
Golden, CO 80402
Phone: (303) 215-9913


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