The thick blue solid line outlines the Yakutat terrane. The white circle indicates the epicentre of the low-frequency tectonic tremors, and the light blue dashed line shows the area where the tectonic tremors occurred, which is used in Figures 2 to 4. The area inside the pink dashed box is the model region used in this study, and the pink dashed line down the center of the box divides the model region into northeast and southwest areas, and represents the boundary between the subducted Yakutat terrane and the subducted Pacific plate in the model. The black lines indicate the isodepth contours of the upper surface of the subducted oceanic plate (with a contour interval of 20 km), red arrows show the plate motion velocity in the Aleutian Trench, and the red triangles indicate volcanoes. CREDIT Iwamoto, K., Suenaga, N. & Yoshioka, S. Relationship between tectonic tremors and 3-D distributions of thermal structure and dehydration in the Alaska subduction zone. Sci Rep 12, 6234 (2022). https://doi.org/10.1038/s41598-022-10113-2

The thick blue solid line outlines the Yakutat terrane. The white circle indicates the epicentre of the low-frequency tectonic tremors, and the light blue dashed line shows the area where the tectonic tremors occurred, which is used in Figures 2 to 4. The area inside the pink dashed box is the model region used in this study, and the pink dashed line down the center of the box divides the model region into northeast and southwest areas, and represents the boundary between the subducted Yakutat terrane and the subducted Pacific plate in the model. The black lines indicate the isodepth contours of the upper surface of the subducted oceanic plate (with a contour interval of 20 km), red arrows show the plate motion velocity in the Aleutian Trench, and the red triangles indicate volcanoes. CREDIT: Iwamoto, K., Suenaga, N. & Yoshioka, S. Relationship between tectonic tremors and 3-D distributions of thermal structure and dehydration in the Alaska subduction zone. Sci Rep 12, 6234 (2022). https://doi.org/10.1038/s41598-022-10113-2
1 Science The Americas 

The Link Between Temperature, Dehydration And Tectonic Tremors In Alaska

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A Kobe University research group has shed light on how low-frequency tectonic tremors occur; these findings will contribute towards better predictions of future megathrust earthquakes.

In addition to the subducting Pacific plate, the Alaska subduction zone is also characterized by a subducting oceanic plateau called the Yakutat terrane. Low-frequency tectonic tremors, which are a type of slow earthquake, have only been detected in the subducted Yakutat terrane area. However, the mechanism by which these events occur is not well understood.

Researchers at Kobe University performed a 3D numerical thermomechanical simulation of thermal convection in the Alaska subduction zone with the aim of revealing the mechanism behind these low-frequency tremors. Based on the 3D thermal structure obtained from the simulation, and the indications of hydrous minerals contained in the slab, the researchers calculated the water content distribution and compared the results of these calculations in the area where the tremors occur.

The results revealed high levels of dehydration in the marine sediment layers and ocean crust in the earthquake region. The researchers believe that the reason the tremors only occur in the Yakutat terrane is because the marine sediment layers and ocean crust are thicker there, which means that the level of dehydration is higher than in the western adjacent Pacific plate (where tectonic tremors don’t occur).

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