Scentific Research

Assistant Researcher Zhang Jiangyang, Researcher Zhang Fan and Distinguished Researcher Lin Jian of the Deep Ocean and Geodynamics Group, Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, together with Professor Yang Hongfeng of the Chinese University of Hong Kong, achieved important progress on research of 3-D bending deformation of the subducted lithosphere in the Mariana Trench. The research was published online in Tectonophysics recently.

The Mariana Trench is located in the floor of the western North Pacific Ocean, with its deepest "Challenger Deep" known as the fourth pole of the earth. Its deep trench is formed by the subduction of the western Pacific plate beneath the Philippine plate. The Plate bends during subduction, and when the stress exceeds the strength of the plates, the plate breaks, resulting in normal faults in the seafloor and inducing earthquakes. Sea water enters the earth's interior through normal faults, and chemically reacts with surrounding mantle rocks, causing rock alteration (called serpentinization). The subducting plate eventually carries fluids deep into the Earth, promoting volcanic activities. Therefore, the research on the deformation of subducting plates is crucial to understanding the circulation of matter and energy in the shallow and deep subduction zones, and the Mariana Trench, the deepest in the world, act as an ideal place to reveal the dynamics of subduction zones.

Taking the Mariana Trench as the object and based on high-precision seabed topography, gravity anomalies, earthquakes and other data constraints, the researchers simulated the 3-D plate bending of the entire Mariana Trench for the first time, calculated the 3-D spatial changes of the bending stress and fracture zone, and revealed that the water fluxes in the southernmost part of the Mariana subducted plate was significantly greater than that in the central and the northern parts. The rupture-yield zone obtained from the theoretical simulation is consistent with the observed surface normal faults, extensional earthquakes, and changes in the plate water-bearing area constrained by seismic wave velocity.

The research revealed the spatial distribution characteristics of the 3-D fracture zone of the Mariana subducted plate, and pointed out the importance of the 3-D bending of lithosphere in the subduction zone. The model can be extended to the research of global subduction zones.

Title of Thesis: Yield failure of the subducting plate at the Mariana Trench

Link: https://doi.org/10.1016/j.tecto.2021.228944

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