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

冬季雪区地震活动监测应在靠近道路的交通便利的地点进行，这些地点总是通过除雪作业开放的。远离除雪路段的场地噪音很大，但由于厚厚的积雪覆盖，没有人能轻易接触到地震仪来采集地震记录以及设备的维护。地震仪必须设置在噪声较大的地点，靠近经常通过除雪作业打开的Roade。这是开发配备地震仪的噪声消除器的动机。两个相同的拾取器垂直于嘈杂的道路线性排列。由于波幅在距离上的吸收非常大，当噪声源靠近监测点时，两个拾取器之间的波信号差异相当大。安装在监测点的两个皮卡距离真实地震的距离几乎相同。基于上述原理，研制了一种STR-110地震仪，它配备了两个拾取器和一个用于选鼻器的微型计算机电路。地震仪记录的波被一个名为MCD的计算机程序处理，以便从噪声中选择地震波。通过对地震波和噪声波的傅里叶分析，编制了MCD程序，利用新开发的STR-110和MCD程序，对24次地震的74个事件、48个噪声和4个未分类进行了分析。共分离出45个噪声，占总噪声的92%。还需要进一步的实验来改进合适的参数，以消除微震监测中的人为噪声。本研究项目还涉及与地压热液系统相关的地震活动监测。1995年新泻北部6.0级地震为地压热液系统与地震活动性的研究提供了一个合适的实例。地压热水正沿着活动断裂发育的断裂带排放到地表。

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.