Earthquake rupture is a process of remarkable complexity. Over the past few decades, scientists have become aware of its high variability on all scales as well as its wide dynamic range. At the same time, a thorough understanding of the seismic source process is a key element of reliable earthquake ground motion prediction. The present book contains a comprehensive collection of contributions originating from the 2012 ECGS Workshop Earthquake Source Physics on Various Scales, held in Luxembourg. The seventeen articles in this volume cover theoretical and observational aspects of the earthquake source process, ranging from tiny, laboratory-generated M -6 events to the source complexity and radiated energy of the world’s greatest earthquakes. Among other aspects, the papers provide new insights into the relationship of earthquake recurrence time with fault frictional parameters, how the results of lab-based friction experiments relate to observational source studies, and how geometrical source complexity can be quantified. In particular, several papers are devoted to the question whether small and large earthquakes scale self-similarly or if they show differences in their dynamic source characteristics, which is one of the most hotly debated aspects of modern seismology. The volume provides an integrated view of the current state-of-the-art knowledge on the earthquake source process on all scales and will be useful to students and professional researchers who are interested in these phenomena.