G. Igarashi et H. Wakita, GEOCHEMICAL AND HYDROLOGICAL OBSERVATIONS FOR EARTHQUAKE PREDICTION IN JAPAN, Journal of Physics of the Earth, 43(5), 1995, pp. 585-598
Several research groups have made efforts to accumulate reliable data
on various geochemical and hydrological parameters for periods longer
than 10 years. The data accumulation has enabled them to characterize
background fluctuations in the data and consequently to examine their
relation to earthquake occurrences without prejudice. As a result, a n
umber of earthquake-related anomalies have consistently been identifie
d in various geochemical and hydrological observations, suggesting tha
t they are sensitive indicators of earthquake occurrence. Comprehensiv
e monitoring based on multicomponent and multi-station observations ha
s begun to result in the detection of more reliable precursory phenome
na which appeared simultaneously in two or different kinds of observat
ions at several stations.