異常変化検出のための長基線地電位への統計モデルの適用

• 高山 寛美

  地震火山研究部

書誌事項

タイトル別名

• Application of statistical models to geoelectric variations with a long electrode span to detect anomalous changes

抄録

We examined two techniques for eliminating components induced by variations of the geomagnetic field to accurately and quickly detect anomalous changes in the geoelectric field, which would enable us to identify crustal signals,. One method is based on a multiple regression model, where any geoelectric variation is presented as a linear combination of the past, present, and future values of geomagnetic variations. The induced geoelectric variation is estimated as a convolution of the geomagnetic variations and the parameters of the obtained regression model. The other method uses BAYTAP-G, by which the observed geoelectric data are separated into four components: 1) tidal, 2) electromagnetically induced, 3) trend, and 4) irregular components. Signals due to volcanic and/or seismic activity may be detected since the trend and the irregular component indicate variations of the self-potential of the crust and/or noise, provided that the amplitudes exceed that of the typical variation. The geomagnetic field at the Kakioka Magnetic Observatory was used as associated data for both methods. These methods were applied to geoelectric variations in the Numazu group, which are contaminated by artificial noise but show anomalous changes. The multiple regression method can apparently eliminate daily variations and telluric storms and can clarify anomalous changes that are not obvious in the original data. However, the gain and phase characteristics calculated from the estimated parameters of the model do not yield information on the underground resistivity structure since the estimated impulse responses do not correctly reflect relationships between the inducing geomagnetic field and the induced geoelectric field due to the presence of excessive artificial noise. BAYTAP-G separates daily variations due to artificial noise as the tidal component and the responses to geomagnetic variations. Anomalous changes are identified in the trend and the irregular component.<br>We investigated the relationship of the tidal component of geoelectric variations estimated by BAYTAP-G with the tidal current and the tide. The correlation between the tidal component of geoelectric variations and tidal currents could not be clarified since simultaneous data of tidal currents with geoelectric variations were not available. Temporal variations of the amplitudes of geoelectric variations of KSM-MTO and tides at OAR for O₁ and M₂ constituents were not correlated despite their high coherencies.

収録刊行物

• 気象研究所研究報告

  気象研究所研究報告 54 (1), 1-45, 2003

  気象庁気象研究所

キーワード

• Atmospheric Science
• Geophysics

詳細情報

• CRID: 1390282681434775808
• NII論文ID: 130004785189
• DOI: 10.2467/mripapers.54.1
• ISSN: 18806643
• ISSN: 0031126X
• 本文言語コード: en
• データソース種別:
  • JaLC
  • Crossref
  • CiNii Articles
• 抄録ライセンスフラグ: 使用不可