Supraslab earthquake clusters above the subduction plate boundary
offshore Sanriku, northeastern Japan: Seismogenesis in a graveyard
of detached seamounts?
Thousands of offshore repeating earthquakes with low-angle thrust
focal mechanisms occur along the subduction plate boundary of NE
Japan. Double-difference relocation methods using P- and S-wave arrivals
reveal clusters of events above these repeating events. To assure
good depth control we restrict our study to events that are close
to seismic stations. These 'supraslab' earthquake clusters are regional
features at depths of 25 to 50 km, and most of these clusters are
below the depth of the forearc Moho, which we determined from converted
waves. Seismicity over this depth range does not occur under the
inland area of NE Japan except just below the vicinity of the arc
volcanoes. Re-entrants in the inner trench slope indicate that repeated
collisions of seamounts have occurred in the past. Our preliminary
interpretation of supraslab clusters is that they represent seismicity
in seamounts detached from the Pacific plate during slab descent,
driven by the resistance of seamounts to subduction. Detachment during
slab descent probably occurs on the sedimented and hydrothermally
altered seafloor on which seamounts were originally constructed since
these are known as zones of weakness during active island growth.
High fluid pressure produced during dehydration of clay minerals
and other low-temperature hydrous minerals could enable detachment
at depths. Seamount crust is thus accreted to forearcs, possibly
leading to a long-term component of near-coastal uplift. Supraslab
earthquake clusters may be our most direct evidence of the fates
of seamounts and suggest that tectonic underplating is actively occurring
in this subduction system.
%0 Journal Article
%1 uchida_etal:2010
%A Uchida, Naoki
%A Kirby, Stephen H.
%A Okada, Tomomi
%A Hino, Ryota
%A Hasegawa, Akira
%D 2010
%J Journal of Geophysical Research
%K geophysics seismology
%N B9
%P B09308+
%R 10.1029/2009JB006797
%T Supraslab earthquake clusters above the subduction plate boundary
offshore Sanriku, northeastern Japan: Seismogenesis in a graveyard
of detached seamounts?
%U http://dx.doi.org/10.1029/2009JB006797
%V 115
%X Thousands of offshore repeating earthquakes with low-angle thrust
focal mechanisms occur along the subduction plate boundary of NE
Japan. Double-difference relocation methods using P- and S-wave arrivals
reveal clusters of events above these repeating events. To assure
good depth control we restrict our study to events that are close
to seismic stations. These 'supraslab' earthquake clusters are regional
features at depths of 25 to 50 km, and most of these clusters are
below the depth of the forearc Moho, which we determined from converted
waves. Seismicity over this depth range does not occur under the
inland area of NE Japan except just below the vicinity of the arc
volcanoes. Re-entrants in the inner trench slope indicate that repeated
collisions of seamounts have occurred in the past. Our preliminary
interpretation of supraslab clusters is that they represent seismicity
in seamounts detached from the Pacific plate during slab descent,
driven by the resistance of seamounts to subduction. Detachment during
slab descent probably occurs on the sedimented and hydrothermally
altered seafloor on which seamounts were originally constructed since
these are known as zones of weakness during active island growth.
High fluid pressure produced during dehydration of clay minerals
and other low-temperature hydrous minerals could enable detachment
at depths. Seamount crust is thus accreted to forearcs, possibly
leading to a long-term component of near-coastal uplift. Supraslab
earthquake clusters may be our most direct evidence of the fates
of seamounts and suggest that tectonic underplating is actively occurring
in this subduction system.
@article{uchida_etal:2010,
abstract = {Thousands of offshore repeating earthquakes with low-angle thrust
focal mechanisms occur along the subduction plate boundary of NE
Japan. Double-difference relocation methods using P- and S-wave arrivals
reveal clusters of events above these repeating events. To assure
good depth control we restrict our study to events that are close
to seismic stations. These 'supraslab' earthquake clusters are regional
features at depths of 25 to 50 km, and most of these clusters are
below the depth of the forearc Moho, which we determined from converted
waves. Seismicity over this depth range does not occur under the
inland area of NE Japan except just below the vicinity of the arc
volcanoes. Re-entrants in the inner trench slope indicate that repeated
collisions of seamounts have occurred in the past. Our preliminary
interpretation of supraslab clusters is that they represent seismicity
in seamounts detached from the Pacific plate during slab descent,
driven by the resistance of seamounts to subduction. Detachment during
slab descent probably occurs on the sedimented and hydrothermally
altered seafloor on which seamounts were originally constructed since
these are known as zones of weakness during active island growth.
High fluid pressure produced during dehydration of clay minerals
and other low-temperature hydrous minerals could enable detachment
at depths. Seamount crust is thus accreted to forearcs, possibly
leading to a long-term component of near-coastal uplift. Supraslab
earthquake clusters may be our most direct evidence of the fates
of seamounts and suggest that tectonic underplating is actively occurring
in this subduction system.},
added-at = {2012-09-01T13:08:21.000+0200},
author = {Uchida, Naoki and Kirby, Stephen H. and Okada, Tomomi and Hino, Ryota and Hasegawa, Akira},
biburl = {https://www.bibsonomy.org/bibtex/2406667e091f7f1ca1b3a44028355f1a7/nilsma},
day = 14,
doi = {10.1029/2009JB006797},
interhash = {e010fb4e45e3ecc24eda05264e91357b},
intrahash = {406667e091f7f1ca1b3a44028355f1a7},
issn = {0148-0227},
journal = {Journal of Geophysical Research},
keywords = {geophysics seismology},
month = sep,
number = {B9},
pages = {B09308+},
timestamp = {2021-02-09T13:26:05.000+0100},
title = {Supraslab earthquake clusters above the subduction plate boundary
offshore Sanriku, northeastern Japan: Seismogenesis in a graveyard
of detached seamounts?},
url = {http://dx.doi.org/10.1029/2009JB006797},
volume = 115,
year = 2010
}