CHARACTERISTIC FEATURES OF FOCAL MECHANISM IN AND NEAR KYUSHU ISLAND (1)

Abstract

The focal mechanisms of earthquakes which occurred in and near Kyushu Island were examined. As a result four seismic zones can be identified and each is characterized by the particularity of focal mechanisms. For the earthquakes which occurred in the western area of the Seto Inland Sea, that is, in the eastern sea region of Kyushu Island, the focal mechanisms could be analyzed in detail because they show a particular feature in comparison with the mechanisms of earthquakes in other seismic zones and are favoured by a good arrangement of observational stations. It may be suggested that the seismicity and the stress distribution do not necessarily enforce the recent hypothesis acknowledged as the plate tectonics.