Estimating Fault Friction From Seismic Signals.
Nearly all aspects of earthquake rupture are controlled by the friction along the fault that progressively increases with tectonic forcing, but in general cannot be directly measured. Here we show that fault friction can be determined at any time, from the continuous seismic signal. In a classic laboratory experiment of repeating earthquakes, we find that the seismic signal follows a specific pattern with respect to fault friction, allowing us to determine the fault's position within its failure cycle. Using machine learning, we show that instantaneous statistical characteristics of the seismic signal are a fingerprint of the fault zone shear stress and frictional state. Further analysis of this fingerprint leads to a simple constitutive law quantitatively relating the seismic signal power and fault friction. These results suggest that fault zone frictional characteristics, and the state of stress in the surrounding rock, can be inferred from seismic waves, which could provide a powerful technique for seismic hazard assessment and earthquake warning systems.
Publisher URL: http://arxiv.org/abs/1710.04172