Graduate student Kohei Matsuda (D3, GRC), Associate Professor Tomohiro Ouchi, and Principal Research Scientist Yuji Higo of the Japan Synchrotron Radiation Research Institute (JASRI), together with their research team, have successfully conducted experiments that provide new insights into the mechanism responsible for “deep-focus earthquakes,” which occur at depths of 400–600 km beneath the Earth’s surface.
Using laboratory earthquake-generation model experiments under high-temperature and high-pressure conditions corresponding to those deep underground, the team demonstrated that faults can form through a crystal structure transformation unique to olivine during deformation. Specifically, the transformation of olivine into a new mineral phase known as poirierite was found to trigger fault formation, ultimately leading to deep-focus earthquakes.
In particular, the Pacific Plate subducting beneath the Ogasawara Islands undergoes intense deformation in the deep mantle, where deep-focus earthquakes are known to occur frequently. The team’s findings suggest that these earthquakes can be explained by the “seismogenic crystal structure transformation” of olivine discovered in this study.
The research results will be published on April 9 in Science Advances, a scientific journal published by the American Association for the Advancement of Science (AAAS).
