Verifications of the noise reduction by down hole sentinel vibration sensors for “Deep-seated landslide detection”
and “Detectable landslide volume” in the Kii peninsula

Tsuneo OHSUMI, Soichi KAIHARA, Ryo SAKAI and Wataru SAKURAI

In order to detect the point of a deep]seated landslide, detection by a sentinel vibration sensor is an effective system for finding the occurrence point of a landslide, the scale of collapse and the occurrence time. The observation points from the sentinel sensing system must be selected carefully, because a high sensitivity sensor needs to sense a low noise level. We must select a location where the ground noise is relatively small. Thus, microtremor measurement is carried out from a carefully selected observation site. The sensor is required to be installed underground because of its sensitivity to other outside noise. We investigated the limitations of the vibration sensors that are capable of detecting the landslide volume, and relationship between epicentral distance and observe vibration of Short Time Average level (STA level) of the landslides. At Goyo site, Noise level (night time) estimated4.7μkine. At this site, the trigger level was2.5(:STA/LTA). Thus, this system was able to exceed the 0.42 million m3 of collapse volume. When the site distance is 20km, this system detect the two million m3 of landslides volume, though this system is not able to detect under one million m3 of landslides volume.