Basic investigation on the earthquake prediction by means of go-electric potential monitoring.

由于短跨距偶极子观测值的不同偶极子长度对VAN方法是必不可少的，因此我们在本研究计划中主要致力于以下两个方面：e.北陆地区，这是方便一些研究人员，和伊豆大岛，在那里得到了一些有趣的结果较早。在前一地区，目前有14个车站在运营。噪音方面，这些车站和希腊的VAN车站一样安静。到目前为止，还没有获得关于SES的确切结果，主要是因为该地区没有发生大规模（M> 5）事件。在后者中，岛上安装了许多当地的短跨度和长跨度偶极子。在冈田NTT偶极附近，出现了一些与过去在东外伊豆震群前出现的异常变化类似的局部变化。但这些变化也与地震无关。在下一个蜂群到来之前，我们无法知道这些变化的性质。在本研究中，通过广泛使用NTT电极，开发了一种网络MT方法。该方法以前所未有的规模和可靠性查明了北海道地下的导电结构。这不仅是对VAN研究的贡献，也是对固体地球科学的巨大贡献。今后，为了事先了解一个台站的敏感性，我们希望与VAN的科学家合作，在希腊敏感和不敏感地区进行彻底的比较地球物理和地质调查，看看它们之间是否存在任何系统性差异。

Recognizing that short-span dipole observations with different dipole length, which is absolutely necessary for the VAN-method, we put major effort in the present research program to the following two areas ; i. e. Hokuriku region, which is conveniently located for some researchers, and Izu Oshima Island, where some interesting results were obtained earlier. In the former area, 14 stations are now in operation. Noisewise these stations are as quiet as VAN stations in Greece. So far, no firm results have been obtained on SES, mainly because there have been no sizable (M>5) event in the region. In the latter, many local short and long-span dipoles have been installed on the Island. Some anomalous changes similar in character as those, which showed an increased occurrence before the Off East Izu seismic swarms in the past, were shown to be localized changes near Okata NTT dipole. But these changes were not correlated with earthquakes either. The nature of the changes in question will not be known until th next swarm comes.In the present research, a NETWORK MT method has been developed through an extensive use of NTT electrodes. The method has clarified th subterranean electrical conductivity structure under Hokkaido with unprecedented scale and reliability. Not only to th VAN research, this was a great contribution to th solid earth geoscience in general. In the future, to know th sensitivity of a station beforehand, we want to make, in cooperation with th VAN scientists, thorough comparative geophysical and geological surveys in both sensitive and insensitive areas in Greece to see if there is any systematic difference between them.