7. Geomagnetic Noises and Detectability of Seismo-magnetic Effect(1)

Geomagnetic total intensity values at various stations in the central part of Japan are examined with the intention of investigating into the accuracy of mutual comparison. The data from stations in the Matsushiro area lead to a conclusion that simple difference values are distributed with a standard deviation slightly smaller than 2γ on quiet days. Use of a mixing technique is suggested for making accidental noises small. A detailed examination of the data from Kanozan and Oshima, 81 km distant from one another, suggests usefulness of a weighted difference technique which leads to a standard deviation smaller than 2γ. Similar study on the data from two stations on Oshima Island brings out an extremely noisy example. No practicable way of correcting the data to an extent cited above is found.|2ヵ所の観測点におけるプロトン磁力計の観測値を比較する場合に,単純な差を作るだけでは,観測点付近の地下構造および人工的雑音のために,地震に伴なう地磁気変化を精度よく検出することがむずかしい.このような雑音は地域ごとにことなっていると思われるので,筆者らは日本全土についてこの種雑音の特性を明らかにすることを目的としている