U.S.-Japan Cooperative Science: Transient Electromagnetic Field Generation on Active Volcanoes-A Comparative Study of the Response from Long Valley Caldera and Aso Volcano, Japan

Geological Survey-Menlo Park, Menlo Park CA

Investigators

Abstract

0003706 Johnston This award supports a three-year collaborative research project between Professor Malcolm Johnston of the Geological Survey in Menlo Park, California and Professor Yoshikazu Tanaka at Kyoto University in Japan. The researchers will be undertaking a study of the transient electromagnetic field generation on active volcanoes: a comparison of the response from Long Valley Caldera in California and the Aso volcano in Japan. The generation of electric and magnetic fields on volcanoes and the relation these have to the role of stress, heat, fluids and gases in volcano processes are fundamental questions that have long gone unanswered because little data is available on active volcanoes and there is a poor understanding of the processes involved. They will bring together the observations on Aso, Unzen and Long Valley's active volcanoes with theoretical and laboratory measurements on self potential generation to provide some understanding on what the data means. They will then separate processes that complicate interpretation of these data and investigate the practical implications that these data have for volcano process monitoring. In particular, they hope to identify the physics involved in generation of self-potential anomalies. They expect to show that the primary contribution to self-potential at temperatures high enough to generate a gas phase arises from gas-related charge transport processes. At lower temperatures, the primary contribution is from electrokinetic effects modulated by elevation effects. The researchers will then quantify these last two effects in field experiments at volcanic areas and also in regions where no volcanic activity has occurred, but known subsurface fluid flow occurs. The project brings together the efforts of two laboratories that have complementary expertise and research capabilities. Results of the research has implications for the detection of active dikes and sills and, more importantly, for detection of changes in intrusion activity. This research advances international human resources through the participation of graduate students. Through the exchange of ideas and technology, this project will broaden our base of basic knowledge and promote international understanding and cooperation. The researchers plan to publish results of the research in scientific journals and report on the findings at scientific meetings.