1:45 PM - 2:00 PM
[SCG58-06] Intraslab hydrated cracks and seismogenesis: insight from anisotropic tomography
★Invited Papers
Keywords:seismic anisotropy, intraslab earthquake, hydrated cracks, seismic tomography
Water entering subduction zones is a crucial incentive for large earthquakes and arc magmas. Plate-bending associated normal faults in the outer-rise area before subduction are invaded by seawater and serpentinized to form hydrated faults and cracks. Subduction of the hydrated faults and cracks with the oceanic lithosphere can be an important transport route for seawater into the deep mantle. However, geophysical evidence for the existence of these hydrated faults and cracks beneath the forearc is still lacking. Recently we determined high-resolution P and S wave tomography and 3-D P-wave anisotropy of the Tohoku forearc by using a great number of arrival-time data of local earthquakes recorded at both the onshore Hi-net and offshore S-net seismic stations (Wang et al., 2022; Zhao et al., 2022). Our updated tomographic method can determine both 3-D velocity heterogeneity and 3-D anisotropy with tilting symmetry axis (Wang & Zhao, 2021). Trench-parallel fast-velocity planes of anisotropy are revealed in the subducting Pacific slab, which intersect the slab upper surface at high angles (~45-90 degrees), reflecting aligned hydrated faults and cracks in the slab. Ruptures of the hydrated faults may cause large intraslab earthquakes such as the 16 March 2022 M7.4 Fukushima–oki earthquake (Wang et al., 2023).
References
Wang, Z., D. Zhao (2021). 3D anisotropic structure of the Japan subduction zone. Science Advances 7, eabc9620.
Wang, Z., D. Zhao, X. Chen (2022). Seismic anisotropy and intraslab hydrated faults beneath the NE Japan forearc. Geophys. Res. Lett. 49, e2021GL097266.
Wang, Z., D. Zhao, X. Chen (2023). Fine structure of the subducting slab and the 2022 M 7.4 Fukushima–oki intraslab earthquake. Seismol. Res. Lett. 94, 17–25.
Zhao, D., Y. Katayama, G. Toyokuni (2022). The Moho, slab and tomography of the East Japan forearc derived from seafloor S-net data. Tectonophysics 837, 229452.
References
Wang, Z., D. Zhao (2021). 3D anisotropic structure of the Japan subduction zone. Science Advances 7, eabc9620.
Wang, Z., D. Zhao, X. Chen (2022). Seismic anisotropy and intraslab hydrated faults beneath the NE Japan forearc. Geophys. Res. Lett. 49, e2021GL097266.
Wang, Z., D. Zhao, X. Chen (2023). Fine structure of the subducting slab and the 2022 M 7.4 Fukushima–oki intraslab earthquake. Seismol. Res. Lett. 94, 17–25.
Zhao, D., Y. Katayama, G. Toyokuni (2022). The Moho, slab and tomography of the East Japan forearc derived from seafloor S-net data. Tectonophysics 837, 229452.