| Co-Investigator(Kenkyū-buntansha) |
ISEZAKI Nobuhiro Chiba University, Faculty of Earth Sciences, Professor, 理学部, 教授 (60107943)
NAGAO Toshiyasu Tokai University, School of Marine Science and Technology, Professor, 海洋学部, 教授 (20183890)
HAYAKAWA Masashi The University of Electro-Communications, Faculty of Electronic Engineering, Professor, 電気通信学部, 教授 (80023688)
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| Research Abstract |
To realize the short-term earthquake prediction with using electromagnetic approach, developments of methodologies for automatic detection of anomalous changes and noise reduction in the seismo-electromagnetics measurements. The main results are as follows.
(1)As for the automatic detection of anomalous changes in the time series data, signal predictors with a linear adaptive filter concept and a nonlinear neural network filter concept has been developed, estimates the next datum in time series using the past data. The designed predictor is applied to the automatic detection of a transient signal in the upper atmospheric physics, Trimpi effect. The results show that both are good at good SNR but NNF is superior when SNR is bad.
(2)The signal discrimination methods for seismo-electromagnetics have been developed and examined. They are principal component analysis (PCA), fractal analysis, and interstation transfer function (ISTF) method using wavelet transform. PCA is applied to the data o
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bserved at the army system in Izu peninsula, which are associated with the 2000 Izu islands earthquake swarm. It is found that a factor associated with solar activity is dominant in the first principal component. In the second principal component, the influence of artificial noise is rather severe, and the third principal component is concerned with the earthquake-related electromagnetic phenomena. Results of the fractal analysis of ULF magnetic variations indicate that the stage seems to be critical (SOC) at one month or a few days before the large earthquake.
The ISTF method with wavelet transform has been developed for remove global external source fields originated from solar-terrestrial interaction. The results show the external field variations are almost removed successfully in both magnetic and electric fields (t<1,000sec). The residual includes the regional signals such as artificial noises and earthquake-related signals. The signal separation between artificial and earthquake-related is future problem. Less
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