Metastable state preceding shear zone instability: Implications for earthquake-accelerated landslides and dynamic...

Area of Science:

• Geophysics and Seismology
• Granular Physics
• Geotechnical Engineering

Background:

• Current landslide prediction models inadequately capture the physical mechanisms of dynamic triggering.
• Understanding granular shear zone behavior under cyclic loading is crucial for earthquake-induced landslide research.
• The transition from static to rapid landslide runout remains poorly understood.

Purpose of the Study:

• To investigate the inherent physics of granular shear zones under dynamic loading.
• To identify precursors to shear zone instability and dynamic triggering.
• To explain postseismic landslide movement observed after earthquakes.

Main Methods:

• Utilized ring shear experiments to simulate dynamic loading on granular shear zones.
• Analyzed coseismic slip and postseismic creep under varying cycles of dynamic loading.
• Characterized the transition from solid-like to fluid-like granular flow.

Main Results:

• Observed significant postseismic creep, increasing with dynamic loading cycles, indicating shear zone fatigue and healing.
• Identified a metastable state, marked by increased postseismic creep, preceding shear zone instability.
• Demonstrated a phase transition from solid-like to fluid-like behavior at the metastable state.

Conclusions:

• The metastable state, characterized by weakened shear resistance, may serve as a precursor to landslide instability.
• The proposed mechanisms provide a framework for understanding postseismic landslide movement.
• Integrating these findings into predictive models like the Newmark method can enhance landslide displacement predictions.