Mechanics of Earthquake Source Processes: Insights from Numerical Modeling

Many major faults separate two tectonic plates that slowly move past each other in opposite directions. The relative motion is accommodated by faults by both sudden dramatic rupture events perceived as earthquakes and much slower, quasi-static fault slips. We study the mechanics of these rupture processes using dynamic-fracture ideas and continuum-mechanics modeling that incorporates laboratory-derived fault friction laws [1, 2, 3], shear heating, and effects of pore fluids [4, 5, 6]. The modeling can reproduce all stages of the past behavior of some fault segments—including locked, slowly moving, and earthquake-producing—with remarkable qualitative, and often quantitative, agreement. In part, it reveals the potential physics behind the unexpected extreme events, such the 2011 Mw 9.0 Tohoku earthquake in Japan [6, 7] that caused up to 40-m tsunami and numerous casualties. The modeling has been used to study situations in which energy-related quantities estimated from seismic shaking based on traditional fracture mechanics theory are valid and when they are not [8]. Such continuum-mechanics-based models, when further developed, will enable us to incorporate our increasing understanding of earthquake source physics into the assessment of seismic hazards and seismicity response to perturbations of natural or anthropogenic origins