Search

In this study, we investigated the relationship between the strain accumulation before a slow slip event (SSE) and the strain release during the SSE for three recent SSEs along the Suruga Trough, Sagami Trough, and Nankai Trough, which are subduction zones in central to southwest Japan. The three analysed SSEs were the 2013–2016 Tokai long-term SSE (L-SSE), the 2018 Boso-Oki short-term SSE (S-SSE), and the 2019–2021 Central Shikoku L-SSE. We applied exponential and logarithmic functions to remove the postseismic deformations caused by the Mw 9.0 2011 Tohoku-Oki earthquake. We discovered a strong negative correlation between strain accumulation and strain release in the dilatation of all three SSEs and in the maximum shear strain of the 2018 Boso-Oki S-SSE. A comparison of the amount of strain accumulation with that of strain release revealed that approximately 30% of the strain was released in the 2013–2016 Tokai L-SSE, that 40% of the strain was released in the 2019–2021 Central Shikoku L-SSE, and that approximately 60% of the strain was released in the 2018 Boso-Oki S-SSE. This finding suggests that all of the accumulated strains are not necessarily released by the SSEs. [ABSTRACT FROM AUTHOR]

The transition from cold forearc to hot arc is considered fundamental to subduction dynamics. However, the range and depth of the cold nose changing significantly along the strike are difficult to constrain. By incorporating the three‐dimensional high‐resolution slab topography and MORVEL plate motion field to constrain thermomechanical modelling, we estimate the subduction thermal state and petrological dehydration in Izu‐Bonin. The multilayered hydrothermal regime gradually transitions from cold to less cold forearc, associated with a large‐scale subduction dewatering process varying along the strike. The dehydration embrittlement resulting from eclogitization and harzburgitization influences the occurrence of fast to slow earthquakes on megathrusts. Impressively, the cold nose is constrained to a depth of 60 km between the arc and Moho‐depth plate interface. The lowered temperature and delay of rock harzburgitization in the cold center of the subducted plate at depth contribute to the occurrence of deep earthquakes below the hot backarc interface. [ABSTRACT FROM AUTHOR]