Development of Equipments Installed in Observation Tunnels and Some Results in Earthquake Prediction

Abstract

This paper reviews of the results of crustal movement observations conducted in Nagoya University. The results are divided into two categories: the first concerns the development of instruments, and the second is related to the research on variations in underground water level. In the first category, we carried out experiments using newly-designed electronic circuits featuring low-cost IC's, and confirmed the long-term stability and reliability of the circuits. We also carried out observation by using silica-tube extensometers equipped with two or three detectors on one component to detect strain steps associated with earthquakes. Our suspension system of silica-tube extensometer is also discussed in this paper, since it is very important in detecting strain step and dynamic strain changes associated with earthquakes. In the second category, we discovered an abnormal increase in groundwater discharge associ ated with earthquake occurrence in a observation tunnel in 1969 using a newly developed equipment. It was found that long-term crustal movements were influenced by changes ingroundwater discharge. We also investigated the strain responses observed after rainfall and succeeded in calculation them using a tank model of precipitations. Abnormal strain re sponses to rainfall are frequently observed before and after earthquake occurrence.