Transition regimes for growing crack populations

Area of Science:

• Geophysics
• Material Science
• Computational Geology

Background:

• Observational studies suggest cracks self-organize into patterns, but mechanisms remain unclear.
• Understanding crack population evolution is crucial for geological and material sciences.

Purpose of the Study:

• To investigate the time and space evolution of normal faults using a spring-block analog model.
• To explore how slip-weakening friction, strain-hardening, and yield strength influence crack population dynamics.

Main Methods:

• Utilized a spring-block analog model simulating brittle layer coupled to a ductile substrate.
• Employed linear stability analysis for friction regimes and numerical simulations for crack interactions.
• Scaled the problem to a single parameter: slip weakening.

Main Results:

• Crack length distributions transition from exponential (nucleation) to power-law (growth) to exponential (coalescence) with increasing strain.
• Observed distinct fault distributions in continental (power-law) and oceanic (exponential-like) settings, interpreted as different evolutionary stages.
• Demonstrated that fault evolution can be approximated as a long-timescale phenomenon, independent of short-timescale earthquake dynamics.

Conclusions:

• The model successfully explains observed fault length distributions and their relation to strain levels.
• Continental and mid-ocean ridge faults represent early and later stages of deformation, respectively.
• The long-timescale approximation is valid, unifying the study of creeping faults and those with earthquakes.