CALVIN KAN

Key question: How do moisture content and grain size influence frictional weakening and compaction in sheared granular materials exposed to acoustic vibration-such as during earth quakes?

Approaches: We systematically varied grain size and fluid content in a rheometer to simulate earthquake-like acoustic vibrations and shear conditions. We monitored key physical responses, including acoustic vibration amplitude, rotor torque, normal force, and sand-layer height, to quantify changes in frictional strength and compaction.

Major takeaways:

• Drier and coarser-grained sand is more susceptible to frictional weakening, shear instability, and compaction under acoustic vibration, highlighting the strong influence of grain size and moisture content on granular-material behavior.
• These findings link sediment properties and moisture conditions to the potential for landslide initiation and dynamically triggered seismicity, providing broader insights into hydro-geodynamic processes within Earth’s crust.

The abstract was accepted for poster presentation at the American Geophysical Union (AGU) Annual Meeting in San Francisco on Dec 7-11, 2026.