DATE2026.01.21 #Press Releases
Serpentinite Indicates “Aseismic Slip”
-Toward Understanding the Relationship Between Slow Earthquakes and Megathrust Earthquakes-
Summary
Associate Professor Takayoshi Nagaya of the Faculty of Education and Integrated Arts and Sciences, Waseda University, and Visiting Collaborative Researcher at the Graduate School of Science, the University of Tokyo (at the start of this study: Lecturer, Faculty of Education, Tokyo Gakugei University; currently Part-time Lecturer at the same faculty), together with Professor Simon Wallis of the Graduate School of Science, the University of Tokyo, have analyzed serpentinite that ascended from the plate boundary of a subduction zone. Their study revealed that antigorite—the principal constituent mineral of serpentinite—deforms the rock as a whole by sliding and rotating along grain boundaries, without significantly changing the shape of individual crystal grains.
The deformation of serpentinite through this newly identified mechanism—grain-boundary sliding of antigorite—is expected to exhibit behavior consistent with “aseismic slip” in subduction zones, similar to the previously proposed deformation mechanism known as dislocation creep. These results suggest that serpentinite at plate boundaries may exhibit aseismic slip behavior at all depths. This finding provides an important foundational insight for understanding the relationship between slow earthquakes and megathrust earthquakes.
This research was published on Wednesday, January 21, 2026, in the international academic journal Progress in Earth and Planetary Science.
Figure：Schematic illustration of serpentinite distributed in the upper mantle (mantle wedge) on the continental plate side of a subduction-zone plate boundary, showing the deformation mechanism of antigorite and the resulting crystallographic preferred orientation revealed by this study.
Links
Waseda University,
Tokyo Gakugei University
Journals
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Journal name Progress in Earth and Planetary ScienceTitle of paper