Abstract
This is the first part of a study dealing with various seismological, geophysical and geological characteristics such as time and space distributions, energy release and focal mechanisms of foreshocks. aftershocks and earthquake swarms. Seismological data of the Japan Meteorological Agency are chiefly made use of.
Before any investigation of foreshock, aftershock and earthquake swarms is undertaken, it is fundamentally important to give a clear definition of these seismic activities which are here tentatively called “ abnormal seismic activities ”. A definition of abnormal seismic activities based on a statistical method is proposed. This method is applied to distinguish abnormal seismic activities from the normal or background seismic activity in one of the seismically active regions in and near the Japanese islands.
