Earthquake prediction studies in Japan

A long-term research program on earthquake prediction in Japan, officially launched in 1965, has made progress. Many of the developments achieved in recent years in various disciplines are outlined. Some of the important findings include: detection of land-deformation by intensified levelling and geodimeter surveys, empirical relations between the extent of a premonitory land-deformation and the magnitude and occurrence-time, and the growth and decay of earthquake swarms accompanied by occurrences of large-scale earthquakes. Operations research on selection of survey areas for levelling and the location of crustal deformation observatories has been made.To process data for earthquake predictions, three centers for different disciplines were set up: in the Geographical Survey Institute, the Japan Meteorological Agency, and the Earthquake Research Institute (University of Tokyo). A newly established committee, called the Coordinating Committee for Earthquake Prediction, which consists of about 30 specialists, analyzes the data flowing into these three channels. The committee issues a warning of earthquake danger, whenever possible.A tentative strategy for achieving earthquake prediction is proposed. An attempt is made to evaluate ratings of earthquake threats on the basis of probability theory.An anomalous land-deformation was found in the South Kanto district, an area south of Tokyo, in 1969. following the strategy, an intensive effort, called Operation South Kanto, aiming at a possible prediction of large earthquakes is now under way. Judging from the results of various earthquake prediction elements, the probability of having an earthquake of magnitude 7 or there-abouts within a period of about 10 yr can not be low if anomalous land-deformation is related to the probability of earthquake occurrence.