Fluid Dynamics in Subduction Zone Processes

Subduction zones are the convergent margins where one tectonic plate plunges beneath another into the mantle. Fluids released by the breakdown of hydrous minerals and by pressure‐temperature changes exert a profound influence on the mechanical behaviour of the plate interface, modulating earthquake genesis, slow slip events and aseismic creep. Fluid migration within the subduction channel alters pore fluid pressures, lowers effective normal stresses on faults and promotes transitions between brittle failure and ductile flow. In the shallow seismogenic zone, elevated fluid pressures can trigger hydrofracturing and facilitate rapid slip, driving megathrust earthquakes. Downdip, where temperatures exceed ~350 °C, dehydration reactions in eclogite and lawsonite‐bearing lithologies supply water into veins and shear zones, sustaining episodic tremor and slow slip. At greater depths, fluid expulsion creates overpressure compartments that govern rheological heterogeneity and influence long‐term forearc uplift. Fluid pathways within mélange, sediments and altered oceanic crust control permeability and strain localisation, with feedbacks between pore fluid pressure, dilatancy, compaction and mineral precipitation. Understanding these processes is vital for assessing seismic hazard, interpreting geodetic signals and modelling long‐term topographic evolution of convergent margins.

Research from Nature Portfolio

Recent high‐resolution seismic imaging has revealed that the plate interface comprises multiple metre‐scale fault planes rather than a single broad band of seismicity, demonstrating that fluid overpressure and fault continuity influence afterslip distribution and earthquake rupture propagation. This refined geometry allows models to account for complex fault interactions during the seismic cycle. In parallel, thermo‐mechanical simulations have shown that transient stripping of subducting slab material at the base of the forearc crust drives periodic uplift and subsidence of coastal topography on million‐year timescales. These pulsing surface oscillations reflect intervals of increased fluid‐assisted accretion at the interface, linking deep fluid‐rock interactions to forearc landscape evolution worldwide.

Research from all publishers

Modelling of fault zone fluid transport has demonstrated that compaction‐driven pressurisation and dilatant weakening control the recurrence of large earthquakes and the initiation and arrest of slow slip sequences. Despite modest changes in porosity, fluid flux remains high near slip fronts, highlighting the importance of porosity evolution in regulating pore pressure. Thermodynamic models of oceanic crust dehydration at depths of episodic tremor and slow slip predict that chlorite and lawsonite breakdown release 1–2 wt % H₂O within narrow pressure‐temperature windows, supplying sufficient in situ fluids to sustain high pore pressures without requiring up‐dip fluid migration. Geological and geophysical synthesis of exhumed mélanges and modern geodetic data supports a habitat of near‐lithostatic pressures in the slow slip source region, where mixed brittle‐viscous deformation of interlayered lithologies and crack‐seal veining record repeated fluid‐assisted shear, underpinning episodic tremor and slow slip mechanisms.

Fluid Dynamics in Subduction Zone Processes publication trend

The graph below shows the total number of articles in fluid dynamics in subduction zone processes across all publications each year (not limited to Nature Index journals).

Technical terms

Subduction channel: The zone of mixed sediments, altered basalt and mélange between the downgoing and overriding plates, accommodating most of the plate convergence.

Pore fluid pressure: The pressure of fluids within rock pore spaces; elevated pore pressures reduce effective stress on faults.

Dehydration reaction: Mineral breakdown induced by increasing pressure and temperature that liberates water into the surrounding rock.

Slow slip event (SSE): A transient fault slip phenomenon lasting days to years, releasing strain without generating high‐frequency seismic waves.

Episodic tremor and slip (ETS): A coupled seismic and aseismic process characterised by low‐frequency seismic tremor and slow fault slip downdip of the seismogenic zone.

Hydrofracturing: The creation of fractures when pore fluid pressure exceeds the tensile strength of the rock.

References

1. Seismological evidence for a multifault network at the subduction interface. Nature (2024).
2. Influence of Creep Compaction and Dilatancy on Earthquake Sequences and Slow Slip. Journal of Geophysical Research: Solid Earth (2023).
3. An Explanation of Episodic Tremor and Slow Slip Constrained by Crack‐Seal Veins and Viscous Shear in Subduction Mélange. Geophysical Research Letters (2018).
4. Transient stripping of subducting slabs controls periodic forearc uplift. Nature Communications (2020).
5. Slab dehydration in warm subduction zones at depths of episodic slip and tremor. Earth and Planetary Science Letters (2020).