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Variations of fluid pressure within the subducting oceanic crust and slow earthquakes
Author(s) -
Kato Aitaro,
Iidaka Takashi,
Ikuta Ryoya,
Yoshida Yasuhiro,
Katsumata Kei,
Iwasaki Takaya,
Sakai Shin'ichi,
Thurber Clifford,
Tsumura Noriko,
Yamaoka Koshun,
Watanabe Toshiki,
Kunitomo Takahiro,
Yamazaki Fumihito,
Okubo Makoto,
Suzuki Sadaomi,
Hirata Naoshi
Publication year - 2010
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 - 10.1029/2010gl043723
Subject(s) - geology , crust , oceanic crust , seismology , subduction , mantle wedge , fluid pressure , convergent boundary , mantle (geology) , plate tectonics , slip (aerodynamics) , geophysics , petrology , tectonics , mechanical engineering , physics , engineering , thermodynamics
We show fine‐scale variations of seismic velocities and converted teleseismic waves that reveal the presence of zones of high‐pressure fluids released by progressive metamorphic dehydration reactions in the subducting Philippine Sea plate in Tokai district, Japan. These zones have a strong correlation with the distribution of slow earthquakes, including long‐term slow slip (LTSS) and low‐frequency earthquakes (LFEs). Overpressured fluids in the LTSS region appear to be trapped within the oceanic crust by an impermeable cap rock in the fore‐arc, and impede intraslab earthquakes therein. In contrast, fluid pressures are reduced in the LFE zone, which is deeper than the centroid of the LTSS, because there fluids are able to infiltrate into the narrow corner of the mantle wedge, leading to mantle serpentinization. The combination of fluids released from the subducting oceanic crust with heterogeneous fluid transport properties in the hanging wall generates variations of fluid pressures along the downgoing plate boundary, which in turn control the occurrence of slow earthquakes.