Most books on earthquakes that are written by geophysicists focus on se- motectonics and analyses of earthquake waves recorded on seismographs in termsofseismic-sourceparameterssuchasseismicmoment,focuslocationand depth, and rupture parameters. In contrast, traditional textbooks of tect- ics and structural geology that are written by geologists are generally based on the principles of geology in terms of both their subject matter and the approach taken to studying the evolution of Earth. While Yeats et al. (1997) wrotea comprehensivetextbook onthegeologyofearthquakes,including c- erage of active global tectonics and paleoseismic studies, we have yet to see a book that focuses on earthquake-source materials that are produced or - formed by both seismic faulting and aseismic creep within seismogenic fault zones at di?erent levels in the crust. The current book, Fossil Earthquakes: Formation and Preservation of Pseudotachylytes, addresses this shortcoming, focusing on the mechanisms and processes of formation of pseudotachylyte and related earthquake ma- rials that form within natural fault zones and those that are generated - ti?cially in high-velocity frictional experiments. The content of the book is largely based courses that I taught on Earthquake Geology and Structural Geology, beginning as lecture notes for undergraduate and graduate students of Earth Science at Shizuoka University, Japan. I hope that the book helps to bridgethe gapbetweenseismologyand geologyand that it encouragesfurther studies of earthquake mechanisms and seismic faulting processes.