[S-CG54] New Insights of Fluid-Rock Interactions: From Surface to Deep Subduction Zone

[SCG54-11] Runaway Slip in a Fault Rock Analog under Shear Stress-Constrained Conditions

*Miki Takahashi¹ (1.Institute of Earthquake and Volcano Geology, Geological Survey of Japan, AIST)

Keywords:maximum strength, runaway slip

I conducted laboratory experiments using a brine-saturated halite-muscovite mixture as a rock analog to investigate slip acceleration in fault rocks under conditions governed by a flow mechanism, specifically pressure solution creep. When shear stress was increased, slip velocity stabilized at a steady-state value as long as the shear stress remained below the maximum strength of the fault rock analog. However, exceeding this strength triggered runaway slip, accompanied by dynamic weakening.
Notably, runaway slip was suppressed as long as the rock analog temporarily regained strength through slip acceleration, delaying its onset by several hours. This delay could be further extended when flow mechanisms were more pronounced. Conversely, the onset of runaway slip was governed by crack connectivity and associated dilation.
Our findings suggest that imminent mega-earthquakes could be predicted if both the slip velocity at the fault’s maximum strength and the critical velocity at which further slip acceleration fails to sustain the fault's strength are known in natural settings. These results highlight the potential of slip velocity monitoring as a predictive tool for mega-earthquakes.