Earthquake Nucleation and Foreshock Mechanisms: cascade triggering, pre-slip, or fluid flows?

Understanding the nucleation process of large earthquakes is crucial for accurate earthquake prediction and seismic hazard mitigation. While earthquake nucleation process has been widely observed in the laboratory and numerical simulation, it is difficult to observe them directly in the field. Some studies have considered foreshocks as the by-product of such nucleation process. Many large earthquakes also have foreshocks, but it is currently impossible to effectively distinguish foreshocks from ordinary earthquake sequences. In addition, the physical mechanism of foreshock generation is still in debate. In this talk I first summarize foreshock observations in the last decades, and present several foreshock mechanisms: cascade-triggering, pre-slip, fluid diffusions, or a combination of them. Next, I present several case studies of foreshocks, focusing on how different results/conclusions can be made by different dataset/methods. Finally, I offer some suggestions on how to move forward on the research topic of earthquake nucleation and foreshock mechanisms.

To be added to the EPS colloquium mailing list, please contact Caroline Carr (carolinecarr@fas.harvard.edu).