| 摘要 |
An earthquake detector is provided for mounting on a structural member of a building or the like, which is resistant to false alarms arising from door slamming, traffic, running, sonic booms, etc., and yet which is sensitive to earthquakes and especially to P-waves which often precede destructive S-waves. The apparatus includes a motion detector for generating an alarm signal, which is responsive only to vibrations below a frequency of about 14 Hz, to avoid false alarms from non-earthquake vibrations. The detector can include a cantilevered beam device with a weight on its free end, and which generates a signal as the weight moves up and down, and a filtering circuit that passes primarily signal components of a frequency between 3 and 14 Hz. The beam device preferably is highly damped so its response is only slightly higher at its resonance frequency than at other frequencies.
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