I was lucky to be able to work with such extra-ordinary people, Bob Geller, Tetsuzo Seno, and Norm Sleep, as my senior scientists. Bob-sensei, Seno-san and Norm have taught me what is a true scientist and not; what is a true Japanese and not; what is a true human being and not; not respectively and maybe respectably. Bob made me to realize that asking questions was the most important thing in geophysics and that whether or not you find answers did not matter. Seno-san showed me that there were no difference between questions and answers. Norm proved me that every question had infinite number of answers and that what was important was to choose the right one.
I thank Bob Geller for his general deep understanding of me as an advisor and for his support of my work. He let me to do whatever I wanted to do and let me to say whatever I wanted to say. I appreciate his tolerance and am very happy that my tongue is still here. Nobody on this Earth except him could be my advisor. Although none of my work with Bob is presented in this thesis, his influence can be seen everywhere. Nagai Aida Arigato Gozaimasita !!
I thank Seno-san for being a co-worker on Chapter 2. He let me to use some of his data in this thesis. He also introduced me that there was something called `double seismic zone', which turned out to be the theme of this thesis.
I thank Norm for just being Norm. You are so wonderful, Norm! I wish you knew how to cook fish, though.
I enjoyed being with my graduate fellows of the Geller/Sleep 385G/H group; Shi-Chen Wang, Glenn Kroeger, Joe Stefani, Sandra Morris, Rick Schult, Jan Morton, Eric Peterson, Rob Haar, Andy Michael, Paul Layer, Doug Wilson and Les Nakae. I thank them for their friendship and encouragements. I especially thank Glenn, my ghost office-mate, for letting me to use his computer program and for his selfish and un-selfish devotion to our computer as a system programmer; Joe for number of stimulating discussions on geophysics and science in general and for `the moon'; and Rick for picking me up at the S.F. airport on the first day of my stay at Stanford and for everything. I also thank the faculty members and the secretarial staff of the Geophysics Department for general help and J. Daniel, J. Walker and Mr. Smirnoff for their companionship. The ways of life of M. Miyamoto and Miss Oshin also encouraged me very much. I thank Stevie Wonder. I liked your song from the bottom of my heart.
I am grateful to the Japan Ministry of Education and NSF for supporting me through their fellowship and grants EAR80-19457, EAR80-19463, EAR81-08718, EAR82-18961, EAR83-06555, respectively.
I thank Dr. D. Giardini of Harvard University for sending me a tape of CMT solutions and Dr. Fumiko Tajima of University of Texas for JHD program. Eric Peterson and Gay Bradshaw kindly read this thesis and made a lot of comments. I deeply appreciate their help.
I especially thank my parents and brother for their understanding, encouragements and love. It was my four-years-older brother (not Carl Sagan) who showed me all the wonderful world of physical sciences in my childhood and had lead me there, although I ended up struggling in the jungle of geophysics. I would like to dedicate this thesis to them and to everything that has been broken, including my left clavicle, my heart and the subducted slabs.
Finally, I thank my wife for her loving support and all the ....... woops, I forgot to have one.