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Heating, weakening and shear localization in earthquake rupture
James R Rice1,2
1School of Engineering and Applied Science, Harvard University, Cambridge, MA, USA rice@seas.harvard.edu.
Summary
Rapid earthquake slip causes frictional heating, dramatically weakening faults. This explains how faults localize to narrow zones, even with high static friction, fitting observational data on heat and melt production.
Area of Science:
- Geophysics
- Tectonophysics
- Rock Mechanics
Background:
- Earthquake fault zones exhibit shear localized to narrow zones (0.1-10 mm).
- Understanding fault weakening mechanisms is crucial for seismic hazard assessment.
Purpose of the Study:
- To investigate how frictional heating during rapid slip promotes intense shear localization in earthquake faults.
- To reconcile theoretical predictions of fault weakening with field observations.
Main Methods:
- Analysis of field and borehole observations of active fault zones.
- Theoretical modeling of frictional heating effects in dry and fluid-bearing fault gouge.
- Comparison of model predictions with earthquake slip rates and heat flow data.
Main Results:
- Flash heating significantly weakens dry rock surfaces at slip rates >0.1 m/s.
- Fluid presence in fault gouge further enhances weakening and localization.
- Observed fault localizations are consistent with dynamic friction coefficients as low as 0.1, contrasting with static friction of 0.6-0.8.
Conclusions:
- Frictional heating is a primary mechanism for intense shear localization in earthquake fault zones.
- The proposed weakening mechanisms explain the narrowness of observed shear zones and low surface heat flow.
- These findings advance our understanding of earthquake behavior and fault mechanics.
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