Geochemical Indicator of Tectonic Stress Resulting in an Earthquake in Central Japan, 1984
RYUICHI SUGISAKI 1 and
TUTOMU SUGIURA 2
1 Department of Earth Sciences, Nagoya University, Chikusa, Nagoya 464, Japan
2 Department of Chemistry, Aichi Kyoiku University, Kariya 448, Japan
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 deepseated fluids being squeezed to the surface by the tectonic stress that caused the earthquake.
Submitted on April 8, 1985
Accepted on June 25, 1985
