著者

川北 優子 酒井 慎一

出版者

東京大学

雑誌

東京大學地震研究所彙報 (ISSN:00408972)

巻号頁・発行日

vol.84, no.2, pp.127-139, 2010-01-28

---

The Special Project for Earthquake Disaster Mitigation in the Tokyo Metropolitan Area has been ongoing (2007−2012). Under this project, the Metropolitan Seismic Observation network (MeSO-net), which consists of about 400 observation sites, has been constructed. The correlations of waveform from local and teleseismic events are high because observation sites are deployed at about 2 or 3-km intervals. In addition, the later phase is easily identified although artificial noise is very intense. However, we are attempting to improve quality by characterizing the various types of noise. In the metropolitan area, various human activities are observed that generate noise such as trains, automobiles, aircrafts, factories, and electrical power. These adversely affect our observations. We recognize various types of noise from continuous records. A spectral graph and a spectrogram in each station are useful for characterizing signals and noise. We also discovered a form of system noise obtained from the relationship between sensor and electrical circuit. We named it Aurora Noise. The strength of Aurora Noise was reduced by improving the electrical circuit. Our study will lead to improving the quality of observed data, and contribute to a new assessment of seismic hazard in the Tokyo Metropolitan Area in Japan.