Improvement of micro-earthquake monitoring method in large scale landslides in snowy areas

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Monitoring of seismic activity in snowy area in winter should be done at easily accessible sites close to roads which are always open by snow removing operation. The noise at sites far away from snow removed roade is very quite, however, no body can easily be access seismograph due to thick snow blanket to collect seismic records as well as the maintenance of the equipments. The seismograph have to set at noisy site, which is close to roade always opened by snow removing operation. This is a motivation to develop a noise eliminator equipped seismograph.Two same pickups are linearly arranged perpendicular to a noisy road. As the absorption of wave amplitude is very large in terms of distance, the difference of wave signals between two pickups is considerably large when the noise source is close to the monitoring sites. Distances from real earthquake are almost same for two pickups installed at monitoring site. Based on the above principle, a seismograph named as STR-110 equipped with two pickups and a micro computer circuit working for nose selector is developed. Waves recorded by the seismograph are treated by a computer program named MCD to select seismic waves from noises. MCD program is developed by the Fourier analysis of seismic waves and noise waves.Using newly developed STR-110 with MCD program, 74 evens consist of 24 earthquakes, 48 noises and 4 unclassified are analyzed. 45 noises are separated, which correspond to 92 % of total noises. Further experiments are required to improve suitable parameters to eliminate man made noise during micro earthquake monitoring.This research project also involves monitoring of seismic activity in relation to geopressured hydrothermal system. The 1995 Northern Niigata Earthquake with M 6.0 provide suitable example for a case study of geopressured hydrothermal system and seismic activity. Geopressured thermal water is discharging up to surface along fractured zones developed along active faults.