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Depth variations in seismic velocity in the subducting crust: Evidence for fluid‐related embrittlement for intermediate‐depth earthquakes
Author(s) -
Shiina Takahiro,
Nakajima Junichi,
Matsuzawa Toru,
Toyokuni Genti,
Kita Saeko
Publication year - 2017
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl071798
Subject(s) - geology , crust , seismology , oceanic crust , ridge , slab , seismic velocity , geophysics , seismic wave , subduction , petrology , tectonics , paleontology
We investigated seismic wave velocity in the subducting crust of the Pacific slab beneath eastern Hokkaido, northern Japan. To detect depth‐dependent properties of the seismic velocities in the crust, we analyzed guided waves that propagate in the crust and estimated P wave velocity ( V p ) of 6.5–7.5 km/s and S wave velocity ( V s ) of 3.6–4.2 km/s at depths of 50–100 km. The results show that the obtained V p and V s are 10–15% lower than those expected for the fully hydrated mid‐ocean ridge basalt, suggesting the existence of aqueous fluids by ~1 vol % in the crust at this depth range. Our observations suggest that overpressurized fluids channeled in the subducting crust plays as a dominant factor for facilitating the genesis of crustal earthquakes at intermediate depths.