U.S.-Japan Cooperative Science: Joint Electromagnetic Experiment on Miyaka-Jima Volcano in Japan and in Long Valley Caldera in California

9726321 Johnston该奖项支持加州门洛帕克美国地质调查局的Malcolm Johnston博士和日本东京大学的Yoichi Sasai教授之间为期两年的合作研究项目。研究人员将在日本的三宅岛火山和加州的长谷火山口进行联合电磁实验。电和磁信号长期以来一直被报道与火山活动有关，但观测结果与精确的地下物理现象之间的严格联系仍然难以捉摸。这项研究的重点是被称为“自我电位”（SP）的测量，其中火山过程是驱动连续电流的地下电池。它将包括在日本和加利福尼亚的火山环境中进行仔细的SP测量，特别强调将非火山信号源与火山信号源分开，并与实验室和理论研究进行比较。研究人员将试图量化与岩浆岩脉相关的火山危险，这些岩脉被注入到无法直接采样的深度。研究的目的是确定：(1)活火山内部流体流动和电荷产生过程的相对重要性；(2)高程和流体流动对自电位观测的相对贡献；(3)在三泷岛和猛犸山等活火山上是否可以探测到深部侵入；(4)岩脉冷却并变得更具电阻性，但仍保留足够的热量来驱动流体和气体流动时SP异常的稳定性。该项目汇集了两个具有互补专业知识、研究能力和设备的实验室的努力。研究结果应确定这种方法在确定新的和现有的岩脉和岩基的位置以确定火山危险方面的有用性。通过思想和技术的交流，该项目将扩大我们的基础知识基础，促进国际了解与合作。＊＊＊

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. ***