Abstract
　The principle and procedure of the geochemical earthquake prediction proposed by the author are described and the result of the project is presented. The method utilizes the compositional anomalies of subsurface gases prior to a possible earthquake. The gases stemmed from depths may be emitted from mineral springs, active faults, and other outlets. These gases can be detected by mutual ratios among several gas species. Obseevations showed (1) emission ofdeep seated gas with high He/Ar ratio induced by the earth tide, aad (2) H2 emission from active faults associated with historical earthquakes. The former have been accumulated in the ground and the latter are produced by rock fracturing. Both gases are expected to be discharged from a depth by stress change and fracture resulting in an earthquake. The examples of the gas anomalies observed at some earthquakes showed that monitoring of several gases with automatic gas-chromatographs at several stations can be feasible for earthquake prediction and may be useful for discussion of focal mechanisms.

*名古屋大学理学部
School of Science, Nagoya University