Comparison of the current activity and that in 1962 (M4 and higher)

On examination of the occurrence of M4 and higher events, it appears that there is little overlap between the zones of activity seen in 1962 and the present, and that the current activity can be seen as an extension of that in 1962. However, recognition of the fact that the 1962 activity also included seismic activity in the areas of Kozushima and the sea near Niijima suggests that this region is susceptible to induced seismic activity. It should be noted that the data for the 1962 activity from a reappraisal based on station correction (Hamada, Tanaka, Nishide; 1985). Due to deviations in the station network at that time, there were errors in epicenter location, making the zone appear larger to the northeast and southwest. But when these errors are accounted for, it appears that the 1962 zone was actually arrayed northwest to southeast, similar to the current activity.

Japan Meteorological Agency