Jim-
    The minimum upper frequency of the band of flat response is about 20 Hz. Most sites
where there is strong motion have an f_max of 5-10 Hz, i.e., a frequency above which
earthquake-produced ground accelerations crash because of the low-pass filtering
effects and site response of the Earth. Above this frequency, the spectral amplitude
steeply decays with increased frequency at rates of 12-24 dB/octave (6 dB is a factor
of 2 in amplitude, i.e., a bit-amp; 1 octave is a factor of two in frequency), i.e.,
f**-2 to f**-4. It is important that the instrument have a flat response at least one
octave above f_max so that one can clearly distinguish between instrument and Earth
response.
    At sites that are on rock very close to the epicenter -- Mark Halliday has a PSN
station at site like this in Ben Lomond, near Santa Cruz, CA -- f-max will be higher,
and the instrument should have a flat response to ~50 Hz.
-Edward

JIm Hannon wrote:

> Edward Cranswick wrote:
>
> > PSN-
> >     Having no techno-smarts left, I cannot talk much about hardware/software
> > and all I can do is wave my arms in an attempt to motivate the building of
> > strong motion sensors. The bottom line is that strong motion sensors operate in
> > the range of groundmotion where the rubber of earthquakes hits the road of
> > public consciousness. We have just finished an intial report on what we did in
> > Turkey with respect to strong motion studies, and the website
> > -Edward
> >
> > --
> > Edward Cranswick                Tel: 303-273-8609
> > US Geological Survey, MS 966    Fax: 303-273-8600
> > PO Box 25046, Federal Center    cranswick@........
> > Denver, CO 80225-0046  USA      E.M. Forster said, "Only connect".
> >
>
> Edward,
> You might be able to answer one Techie question I have about strong motion sensors.
> What Upper frequency response would be desirable?
> --
> Jim Hannon
> http://soli.inav.net/~jmhannon/
> 42,11.90N,91,39.26W
> WB0TXL
>
> _____________________________________________________________________
>
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--
Edward Cranswick                Tel: 303-273-8609
US Geological Survey, MS 966    Fax: 303-273-8600
PO Box 25046, Federal Center    cranswick@........
Denver, CO 80225-0046  USA      E.M. Forster said, "Only connect".




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