Journal Article Depth variations in seismic velocity in the subducting crust : Evidence for fluid-related embrittlement for intermediate-depth earthquakes

Shiina, Takahiro  ,  Nakajima, Junichi  ,  Matsuzawa, Toru  ,  Toyokuni, Genti  ,  Kita, Saeko

44 ( 2 )  , pp.810 - 817 , 2017-01-28 , American Geophysical Union
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 6.5-7.5km/s and S wave velocity (V-s) of 3.6-4.2km/s at depths of 50-100km. 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 similar to 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.

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