9726321 Johnston This award supports a two year collaborative research project between Dr. Malcolm Johnston of the U.S. Geological Survey in Menlo Park, California and Professor Yoichi Sasai of the University of Tokyo in Japan. The researchers will be undertaking a joint electromagnetic experiment on Miyake- Jima volcano in Japan and in Long Valley caldera in California. Electric and magnetic signals have long been reported to be associated with volcanic activity, but a rigorous connection between the observations and the precise underground physical phenomena remains elusive. This research focuses on the measurement known as "self- potential" (SP) in which the volcanic process is an underground battery driving continuous electric currents. It will involve careful SP measurements at volcanic environments in Japan and California, with particular emphasis on separating non-volcanic sources of signal from volcanic sources and comparison with laboratory and theoretical studies. The researchers will attempt to quantify the volcanic hazard associated with magmatic dikes that have been injected at depths that are inaccessible to direct sampling. The objectives of the research are to determine: (1) the relative importance of fluid flow and charge generation processes within active volcanoes, (2) the relative contributions to self-potential observations from elevation and fluid flow, (3) whether deep intrusions can be detected on active volcanoes such as Miyake-Jima and Mammoth Mountain and (4) The stability of SP anomalies as dikes cool and become more resistive yet retain sufficient heat to drive fluid and gas flow. This project brings together the efforts of two laboratories that have complementary expertise, research capabilities and equipment. Results of the research should define the usefulness of this method for determining the location of new and existing dikes and sills for volcanic hazard identification. Through the exchange of ideas and technolo gy, this project will broaden our base of basic knowledge and promote international understanding and cooperation. ***
