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Sensor apparatus and method for detecting earthquake generated P-waves and generating a responsive control signal

  • US 20040135698A1
  • Filed: 08/28/2003
  • Published: 07/15/2004
  • Est. Priority Date: 08/30/2002
  • Status: Active Grant
First Claim
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1. Apparatus for detecting earthquake generated P-waves comprising:

  • means forming a housing adapted to be mounted to a supporting structure subject to movement by seismic forces;

    sensor means affixed to said housing and operative to generate electrical signals proportional to motion experienced by said support structure;

    signal amplifying and filtering means responsive to said electrical signals and operative to amplify and pass signals having frequencies within the range of approximately 0.5 to 15 Hz; and

    signal processing means for sampling the passed signals and for performing an automatic realtime offset zeroing function by averaging the signals over successive periods of time greater than approximately 10 seconds, and for taking the ongoing mean of the averaged signals as the zero point, but causing the averaged signal to drop to a “

    zero”

    value after a few seconds of no signal, and for determining that a P-wave has been detected if (a) the averaged signal rises above a predetermined level, and/or (b) the integrated sum rises above a predetermined trigger value within a predetermined window of time, and for generating an output signal commensurate therewith.

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