Nadeau. It was a great collaboration experience, and I learned a lot from each of them.

iii To my parents. iv Acknowledgements First and foremost, I would like to sincerely thank my advisors, Rob Clayton and Nadia Lapusta, for their continuous support and guidance throughout my graduate studies. Rob taught me how to approach the research from the most practical and efficient way. I deeply appreciate his patience, encouragement, and accessibility whenever I needed his help. Na-dia is always willing to spend hours discussing my research. I enjoy her excellent way of explaining complicated physics. I am grateful for her inspiration and countless advice. I am so fortunate to have Rob and Nadia as my advisors, and I will always cherish what I have learned from them. I would like to thank my academic advisor, Joann Stock, for the help with various academic issues. I am very grateful to my other thesis committee members, Pablo Ampuero and Jean-Philippe Avouac, for following my progress, reviewing this thesis, and providing valuable suggestions. I would also like to thank other faculty members at Caltech from whom I have taken classes. Special thanks go to visiting professors Albert Tarantola and Malcolm Sambridge for their great lectures on inverse theory. I also want to thank Jason and Zorka Saleeby for leading the wonderful Hawaii Pahoehoe field trip. I own my gratitude to all the members in Rob’s and Nadia’s research groups. Yi Liu and Yoshi Kaneko helped me through the initial stages of my research on earthquake sim-vulations with their experience and knowledge. I benefited greatly from discussions with YoungHee Kim and Hiro Noda. I would like to acknowledge my colleagues, Kate Chen, Roland Bürgmann, and Rober