Electromagnetic Survey for Environment in Northeast Asia

近10年来，北亚和东亚国家社会制度的剧烈变化，为这一广阔区域的环境研究及其对全球环境变化的影响开辟了新的前景。然而，由于经济快速增长的要求，这一地区的富饶同时也受到了计划外开发的影响。这个国际合作研究项目的最终目的是支持包括俄罗斯、中国和蒙古在内的东北亚国家的健康发展。为此，对电磁地球物理勘探技术的应用和适应进行了研究。电磁技术是快速的，因为传感器，即天线，不必与地面机械接触。此外，EM方法对土壤和岩石中的水分特别敏感。该项目的第一次会议于1998年12月1日在东北大学举行，以选择研究的现场地点。最后一次会议在新西伯利亚的SB RAS地球物理研究所举行，总结了该项目的成果。在为期两年的项目中，分别对北京地区(1998年11月、1999年10月)的低频钻孔雷达资料进行了测试，并于1999年8月在蒙古进行了探地雷达地下水调查，在西伯利亚地区进行了多年冻土调查。利用CMP数据采集方法，可以观测到20米以下的地下水位和多年冻土活动区的状况。利用井眼雷达显示了地下水的评价和探测路径。讨论了用于跨孔测量的天线方向性。论证了探地雷达和合成孔径雷达联合使用的可能性。

The drastic change of the social systems in North and East Asian countries last 10 years, have opened a new vista to environmental studies in this vast region and its effect to the global environmental change. The rich nature in this region is, however at the same time, suffered from unplanned development due to the requirement of rapid economical growth. The ultimate purpose of this international collaboration research project is supporting sound development of Northeast Asian countries including Russia, China and Mongolia. For this purpose, application and adaptation of Electromagnetic Geophysical Exploration Technologies have been studied.The Electromagnetic techniques are fast, because the sensors, I.e., antennas, do not have to have mechanical contract to the ground surface. In addition, EM methods are sensitive especially to water content in soil and rock. It is suitable for ground water survey and other environmental problems.The first meeting of the project was held in Tohoku University 1 December 1998 for selection of field site of the study. The final meeting was held in the Institute of Geophysics, SB RAS, in Novosibirsk, for summarizing the result of the project. During the two-year project, file tests for a low-frequency borehole radar in Beijing (November 1998, October 1999), ground water survey by GPR in Mongolia in August 1999 and Permafrost survey in Siberia in August 1999 were carried out.The major results obtained by this research project are listed below :1. The effectiveness of GPR in dry area was demonstrated. By using CMP data acquisition method, we could observe the ground water level and status of active region of permafrost at the depth of 20m.2. Subsurface evaluation and detection path of water was demonstrated by borehole radar. Antenna directivity for cross-hole measurement was discussed.3. A possibility of the joint use of GPR and SAR was demonstrated.