Basic characteristics of ground vibration sensors for the detection of debris flow

An acoustic sensor has been designed and built to sense ground vibration wi th a microphone installed underground inside a steel pipe. The sensor has d etected debris flows in torrents in Japan. Other sensors have been used to sense ground vibrations similarly and they also have been tested in the fie ld individually. Basic characteristics of three different ground vibration sensors, an acoustic, a piezoelectric, and a moving-coil sensor are compare d in the same test field. Two of them, a microphone sensor and a piezoelect ric sensor, have higher signal-to-noise ratios (S/N ratios) than the moving -coil sensor. The microphone sensor has the maximum S/N ratio at our experi mental field and is the most useful one. (C) 2000 Elsevier Science Ltd. All rights reserved.