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Subduction of thick oceanic plateau and high‐angle normal‐fault earthquakes intersecting the slab
Author(s) -
Arai Ryuta,
Kodaira Shuichi,
Yamada Tomoaki,
Takahashi Tsutomu,
Miura Seiichi,
Kaneda Yoshiyuki,
Nishizawa Azusa,
Oikawa Mitsuhiro
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 - 10.1002/2017gl073789
Subject(s) - geology , seismology , subduction , seamount , slab , fault (geology) , aftershock , crust , oceanic crust , deformation (meteorology) , geophysics , tectonics , paleontology , oceanography
The role of seamounts on interplate earthquakes has been debated. However, its impact on intraslab deformation is poorly understood. Here we present unexpected evidence for large normal‐fault earthquakes intersecting the slab just ahead of a subducting seamount. In 1995, a series of earthquakes with maximum magnitude of 7.1 occurred in northern Ryukyu where oceanic plateaus are subducting. The aftershock distribution shows that conjugate faults with an unusually high dip angle of 70–80° ruptured the entire subducting crust. Seismic reflection images reveal that the plate interface is displaced over 1 km along one of the fault planes of the 1995 events. These results suggest that a lateral variation in slab buoyancy can produce sufficient differential stress leading to near‐vertical normal‐fault earthquakes within the slab. On the contrary, the upper surface of the seamount (plate interface) may correspond to a weakly coupled region, reflecting the dual effects of seamounts/plateaus on subduction earthquakes.