Taiwan Natural Electromagnetic Field Observation

• Main Authors: Han-lun Hsu, 徐漢倫
• Other Authors: Chien-chih Chen
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/50390030804777740867

博士 === 國立中央大學 === 地球科學學系 === 101 === Many electromagnetic anomalies are reported as precursors in many areas. In this study, we tried to build up the stationary recording system to measure the variations of natural electromagnetic field. The preliminary results will show some background changes in our system and variations which may relate to earthquakes and typhoon activities. We found the different daily cycles of resistivity in different frequency bands between Penghu and Fushan station. The solar wind activities would cause the daily changes on the electromagnetic field and also cause the resistivity changes between day and night. We found the statics of resistivity on nighttime data was better than the daytime data in Penghu station. The resistivity would also appear the large anomalies at the beginning of a magnetic storm. The data of the geoelectric field measurement system showed the electric filed in different sites were drifting in different trends in Taiwan in a year. There are two large and long raised on geoelectric field in 2012 and they may all relate to earthquakes. We found the short term changes in many stations and the largest anomaily in Nanau in the earily August and it would be related to the typhoon passed by Taiwan area. There were appeared some harmonic electromagnetic signals in seconds period before earthquake in our magnetotelluric records in Fushan. We also found the small drifting signals earlier then the seismic wave arriving time and the variations may with seismic wave. One large earthquake occurred in central Taiwan in March 2013, and there were recorded some changes just about 30 seconds before and 14 seconds after the earthquake in our geoelectric measuring. The early signal just appeared in stations nearby the epicenter in the central Taiwan. The late signals were found almost at the same time in whole Taiwan.