Stress-driven fluid flow controls long-term megathrust strength and deep accretionary dynamics.

Area of Science:

• Geophysics
• Tectonics
• Earth Science

Background:

• The frictional strength heterogeneity of megathrust earthquake zones is crucial for plate coupling and subduction dynamics.
• The long-term persistence and spatial distribution of high-friction segments are not well understood.

Purpose of the Study:

• To use accretion processes, specifically tectonic underplating, as a proxy for characterizing long-term frictional zonation in subduction interfaces.
• To investigate the influence of tectonic stress variations on fluid transport and its feedback with effective stress in deep fore-arc regions.

Main Methods:

• Numerical thermo-mechanical experiments were conducted to simulate subduction zone processes.
• Analysis focused on the relationship between fluid distribution, effective stress, and the stability of interface frictional properties over million-year timescales.

Main Results:

• Tectonic stress variations significantly control fluid transport in deep fore-arc regions.
• A positive feedback loop between fluid distribution and effective stress stabilizes interface frictional properties over millions of years.
• Thick duplex structures, formed by successive underplating events, indicate segments with increasing frictional behavior.

Conclusions:

• Tectonic underplating serves as a valuable proxy for identifying long-term frictional zonation in megathrust zones.
• The study provides a framework for understanding the long-term hydro-mechanical properties and coupling/decoupling behavior of subduction interfaces globally.
• Recognizing active tectonic underplating aids in mapping segments with potentially higher seismic hazard due to stable high friction.