That faults are the origin of earthquakes was not an accepted theory in Japan for several decades prior to 1960, although the progressive accumulation of fault displacement in the Quaternary Time had been demonstrated in seismic areas. The Earthquake Prediction Program proposed by seismologists in 1962 stimulated geologists and geomorphologists to start active fault studies.
During the 1960-1970's, the following results were made clear: 1) the distribution of active faults in onshore Japan, shown in 123 sheet maps of 1: 200,000 scale with detailed inventories by the Research Group for the Active Faults of Japan; 2) the extensive occurrence of strike-slip type active faults, almost none of which was known on the Japanese Islands at that time; 3) the existence of Quaternary crustal stress field with east-west compression in most of the Japanese Islands, recognized from the conjugate fault system of the central Japan; 4) the quantitative relation between earthquake magnitude and length of the surface trace of co-seismic fault for the onland Japanese earthquakes, which has been used in Japan to estimate magnitudes of future earthquakes; 5) the very long recurrence intervals of activity of a fault, generally longer than the order of 1000 years.
In 1980-1990's, especially after the 1995-Kobe earthquake, excavation studies were performed extensively in more than one hundred active faults in onshore Japan. The active fault data obtained so far made it possible to prepare seismic hazard maps with probabilities of the occurrence of strong seismic motion in a specified period.