Abstract
The origin of the stress field concerning earthquake occurrence is studied, and it is suggested that the concept of antidislocation or passive dislocation is useful for the understanding of the formation of a focal region. This view means that the earthquake occurrence is the release of a locally accumulated elastic strain field. It is shown that some features of the earthquake such as stress concentration on the focal region before an earthquake and aftershocks occurrence are naturally explained with the use of the idea of antidislocation.
