Tectonic Processes and Seismic Hazards in Subduction Zones

Subduction zones arise where one tectonic plate descends beneath another, driving a suite of processes that shape Earth’s surface and generate significant seismic hazards. At these convergent margins, the descending slab interacts with the overriding plate to form an oceanic trench, accretionary wedge and volcanic arc. Mechanical coupling between plates allows elastic strain to accumulate on the interface, ultimately released in megathrust earthquakes, which can exceed magnitude 9 and trigger devastating tsunamis. Sediment accretion, fluid release from the slab and variations in frictional properties lead to segmentation of the subduction interface into locked, creeping and slow‐slip regions, each with distinct seismic potential. Within the forearc, tectonic stress is accommodated by backthrusts, splay faults and the growth of the accretionary prism, influencing rupture propagation toward the trench and landward. Beneath the volcanic arc, dehydration of the slab induces mantle wedge melting and arc volcanism, while oblique convergence promotes strain partitioning into strike-slip structures that further modulate seismicity. Understanding these interrelated processes is crucial for assessment of seismic and tsunami risk, for improvement of geodetic monitoring strategies and for refining regional hazard models.

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Tectonic Processes and Seismic Hazards in Subduction Zones publication trend

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Technical terms

Subduction zone: Region where one tectonic plate sinks beneath another at a convergent boundary.

Megathrust earthquake: A very large earthquake occurring on the subduction interface, often generating tsunamis.

Accretionary wedge: Assemblage of sediments and crustal material scraped off the subducting plate and accumulated at the trench.

Forearc basin: Depressed region landward of the accretionary wedge, bounded by the volcanic arc and trench.

Seismic coupling: Proportion of plate motion that is locked and stored as elastic strain on the subduction interface.

Velocity anomaly: A deviation in seismic wave speed used to infer variations in temperature, composition or hydration.

Tomography: Seismic imaging technique that reconstructs subsurface structures from travel times of seismic waves.

Porosity: Fraction of void space in sediments or rocks, affecting fluid pressure and mechanical behaviour.

References

1. Structure of the central Sumatran subduction zone revealed by local earthquake travel-time tomography using an amphibious network. Solid Earth (SE) (2018).
2. Shallow subsurface morphotectonics of the NW Sumatra subduction system using an integrated seismic imaging technique. Geophysical Journal International (2014).
3. Chapter 13 Anatomy of the AndamanNicobar subduction system from seismic reflection data. Geological Society London Memoirs (2017).