This book focuses on the earthquake source materials produced or deformed by both seismic faulting and aseismic creep within seismogenic fault zones at different levels of the crust. In particular, the mechanisms and processes involved in the formation of earthquake materials are covered also including the principal results of field investigations, analyses of meso-scale and micro-scale textures and structures, laboratory experiments, chemical analyses, conceptual fault models, as well as the implications of fault-related pseudotachylite and its related fault rocks for our understanding of earthquakes. This book is intended to help bridge the gap between seismology and geology and to encourage further studies of earthquake mechanisms and seismic faulting processes.