Geochemical Indicator of Tectonic Stress Resulting in an Earthquake in Central Japan, 1984

Abstract
Conspicuous changes in gas composition were observed at a fumarole and a mineral spring just before the occurrence of an inland earthquake (magnitude, 6.8) in central Japan in September 1984; the fumarole and spring were 9 and 50 kilometers, respectively, from the earthquake's epicenter. Deep-seated fluids emitted as a result of the compressional stress of the earth tide had been observed previously at this mineral spring and at a lava lake in Hawaii. By analogy, the gas anomaly observed before the earthquake in Japan probably resulted from deep-seated fluids being squeezed to the surface by the tectonic stress that caused the earthquake.