I should like to acknowledge my gratitude to Professor TAKASHI FUJII who suggested the subject for my thesis, and provided many discussions on the main themes.

I am also grateful to Professors S. BANNO of Kanazawa University and S. ARAMAKI of the Earthquake Institute, University of Tokyo, for many discussions and suggestions and for reading my thesis. I wish to express my sincere gratitude to Drs. S. YOSHIDA, E. HORIKOSHI, and Y. IKEDA of the University of Tokyo for many discussions and suggestions.

I have been fortunate to have many colleagues at the University of Tokyo who freely provided me with pertinent data and ideas, and with whom I had chal lenging discussions.