A motion detector for detecting earthquakes or the like provides a warning signal when vibrations having a frequency of the order of the natural frequency of an earthquake tremor are detected. A preferred embodiment of the device employs a vertical spring barb member which is mounted on a suitable support...http://www.google.fr/patents/US4689997?utm_source=gb-gplus-shareBrevet US4689997 - Motion detector suitable for detecting earthquakes and the like
Motion detector suitable for detecting earthquakes and the like
