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Low‐frequency tremors, intraslab and interplate earthquakes in Southwest Japan—from a viewpoint of slab dehydration
Author(s) -
Seno Tetsuzo,
Yamasaki Tadashi
Publication year - 2003
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 - 10.1029/2003gl018349
Subject(s) - geology , subduction , seismology , crust , oceanic crust , slab , intraplate earthquake , adakite , embrittlement , geophysics , tectonics , materials science , metallurgy
Low‐frequency tremors (LFT) recently found in the Southwest Japan fore‐arc likely occur due to hydro‐fracturing from fluids leaving the dehydrating Philippine Sea slab. However, there are some places without such LFT; they are N. Izu‐Kanto, E. Shikoku, and S. Kyushu. These are the places where island‐arc type crust is subducting. We propose that dehydration of the subducted crust does not occur beneath these regions, because it is composed mainly of tonalite, lacking the quantity of hydrous minerals seen in normal subducting oceanic crust. We show that almost no earthquake occurs within the subducted crust in such regions, consistent with dehydration embrittlement hypothesis for intraslab seismicity. The lack of dehydration from the crust would also affect the mode of occurrence of interplate earthquakes, because pore fluid pressure is more difficult to rise at the thrust zone. This might be reflected in the irregular occurrence of great earthquakes in these regions.