地殻流体の分布を推定する地球物理―地球化学の統合的手法

抄録

Liquids in the Earth’s interior (aqueous fluid, magma, supercritical fluids, etc.) can transport mass and energy fast because they flow easily, and they also cause chemical reactions with surrounding solid materials, resulting in significant changes in the physical properties such as a decrease in rock strength and melting temperature. For this reason, they are thought to play an important role in seismic and volcanic activities and in the evolution of the entire Earth. However, it is difficult to capture and quantify the distribution where and how much of them exist. In particular, it is difficult to identify various types of rocks and “geofluids” in the crust and uppermost mantle down to about 60 km depth, which is the main site of seismic and volcanic activities, only by analyzing seismic wave propagation or electrical conductivity (or its inverse, resistivity), which are the major conventional imaging methods. Recently, a method has been developed to estimate the types, volume ratios, and distribution geometries of rocks and fluids by integrating analysis of seismic velocity, electrical conductivity, and chemical composition/properties of constituent materials in the Earth’s interior. This paper reviews this method and discusses its potential applications with a new preliminary result.