Abstract
The process of the occurrence of an earthquake is discussed from the mechanical point of view, and it is emphasized that the structural heterogeneity in and around the earthquake source region is one of the most important factors which cause the occurrence of precursory phenomena. Earthquake precursors are classified into the following two types. The one is the precursors which are caused by the increase in stress. In general, long-term precursors are those of this type. The gradual increase of earthquake swarm activity before the 1983 Japan Sea earthquake, the gradual increase in seismic activity in the surrounding region of the 1989 Loma Prieta earthquake before the main shock and the appearence of the seismic gaps of the second kind are discussed as examples of this type. The other is the precursors which are caused by a slowly progressive rupture process just before the sudden main fracture. Short-term precursors are mainly those of tis type. Foreshocks prior to the 1934 and 1966 Parkfield earthquakes are discussed as the typical examples of this type.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Zisin (Journal of the Seismological Society of Japan. 2nd ser.)
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
