Runaway slip to the trench due to rupture of highly pressurized megathrust
beneath the middle trench slope: The tsunamigenesis of the 2011 Tohoku
earthquake off the east coast of northern Japan
The gigantic 2011, March 11 Mw 9 Tohoku earthquake is examined from
the viewpoint of the pre-seismic forearc structure, the seismic reflection
properties of a megathrust around the usual up-dip limit of the seismogenic
zone, the thermal state of a shallow subduction zone, and the dehydration
of underthrust sediments. At the Japan Trench the Pacific Plate is
subducting westward beneath northeast Japan at a dip angle of 4.6
deg. The middle and lower slopes of the landward side dip eastward
at angles of \~2.5 deg and \~8.0 deg, respectively. The forearc
prism beneath the middle and lower slopes is inferred to be in extensionally
and compressively critical states, respectively, based on the presence
of clear internal deformation features and on the occurrence of aftershock
earthquakes. The rapid uplift of the forearc that caused the 2011
Tohoku tsunami may have been associated with this internal deformation
of the prism. The critical state of the prism indicates that the
effective basal friction (mu\_b') of the plate boundary megathrust
is <0.03 for the middle prism and >0.08 for the lower prism. The
megathrust, especially under the middle slope, is characterized by
a prominent reflector with negative polarity. One of multiple possible
explanations is that the megathrust hosts highly pressurized fluids.
Underthrust sediments in this part of the Japan Trench are dominated
by pelagic and siliceous vitric diatomaceous silt with clay. The
dehydration kinetics of opal-A to quartz, the clay transformation
of smectite-illite, and the thermal structure of the Japan Trench
suggest that maximum dehydration of the sediments would take place
at 50-60 km horizontally from the deformation front, where the temperature
along the megathrust is 100-120 deg C. The zone of maximum dehydration
coincides with the prominent seismic reflector that has negative
polarity. We hypothesize a possible free slip along this portion
of the megathrust during the 2011 Tohoku earthquake, caused by anomalously
high fluid pressure resulting from fluid accumulation over centuries.
%0 Journal Article
%1 kimura_etal:2012
%A Kimura, Gaku
%A Hina, Shoko
%A Hamada, Yohei
%A Kameda, Jun
%A Tsuji, Takeshi
%A Kinoshita, Masataka
%A Yamaguchi, Asuka
%D 2012
%J Earth and Planetary Science Letters
%K geophysics seismics seismology
%P 32--45
%R 10.1016/j.epsl.2012.04.002
%T Runaway slip to the trench due to rupture of highly pressurized megathrust
beneath the middle trench slope: The tsunamigenesis of the 2011 Tohoku
earthquake off the east coast of northern Japan
%U http://dx.doi.org/10.1016/j.epsl.2012.04.002
%V 339-340
%X The gigantic 2011, March 11 Mw 9 Tohoku earthquake is examined from
the viewpoint of the pre-seismic forearc structure, the seismic reflection
properties of a megathrust around the usual up-dip limit of the seismogenic
zone, the thermal state of a shallow subduction zone, and the dehydration
of underthrust sediments. At the Japan Trench the Pacific Plate is
subducting westward beneath northeast Japan at a dip angle of 4.6
deg. The middle and lower slopes of the landward side dip eastward
at angles of \~2.5 deg and \~8.0 deg, respectively. The forearc
prism beneath the middle and lower slopes is inferred to be in extensionally
and compressively critical states, respectively, based on the presence
of clear internal deformation features and on the occurrence of aftershock
earthquakes. The rapid uplift of the forearc that caused the 2011
Tohoku tsunami may have been associated with this internal deformation
of the prism. The critical state of the prism indicates that the
effective basal friction (mu\_b') of the plate boundary megathrust
is <0.03 for the middle prism and >0.08 for the lower prism. The
megathrust, especially under the middle slope, is characterized by
a prominent reflector with negative polarity. One of multiple possible
explanations is that the megathrust hosts highly pressurized fluids.
Underthrust sediments in this part of the Japan Trench are dominated
by pelagic and siliceous vitric diatomaceous silt with clay. The
dehydration kinetics of opal-A to quartz, the clay transformation
of smectite-illite, and the thermal structure of the Japan Trench
suggest that maximum dehydration of the sediments would take place
at 50-60 km horizontally from the deformation front, where the temperature
along the megathrust is 100-120 deg C. The zone of maximum dehydration
coincides with the prominent seismic reflector that has negative
polarity. We hypothesize a possible free slip along this portion
of the megathrust during the 2011 Tohoku earthquake, caused by anomalously
high fluid pressure resulting from fluid accumulation over centuries.
@article{kimura_etal:2012,
abstract = {The gigantic 2011, March 11 Mw 9 Tohoku earthquake is examined from
the viewpoint of the pre-seismic forearc structure, the seismic reflection
properties of a megathrust around the usual up-dip limit of the seismogenic
zone, the thermal state of a shallow subduction zone, and the dehydration
of underthrust sediments. At the Japan Trench the Pacific Plate is
subducting westward beneath northeast Japan at a dip angle of 4.6
deg. The middle and lower slopes of the landward side dip eastward
at angles of \~{}2.5 deg and \~{}8.0 deg, respectively. The forearc
prism beneath the middle and lower slopes is inferred to be in extensionally
and compressively critical states, respectively, based on the presence
of clear internal deformation features and on the occurrence of aftershock
earthquakes. The rapid uplift of the forearc that caused the 2011
Tohoku tsunami may have been associated with this internal deformation
of the prism. The critical state of the prism indicates that the
effective basal friction (mu\_b') of the plate boundary megathrust
is <0.03 for the middle prism and >0.08 for the lower prism. The
megathrust, especially under the middle slope, is characterized by
a prominent reflector with negative polarity. One of multiple possible
explanations is that the megathrust hosts highly pressurized fluids.
Underthrust sediments in this part of the Japan Trench are dominated
by pelagic and siliceous vitric diatomaceous silt with clay. The
dehydration kinetics of opal-A to quartz, the clay transformation
of smectite-illite, and the thermal structure of the Japan Trench
suggest that maximum dehydration of the sediments would take place
at 50-60 km horizontally from the deformation front, where the temperature
along the megathrust is 100-120 deg C. The zone of maximum dehydration
coincides with the prominent seismic reflector that has negative
polarity. We hypothesize a possible free slip along this portion
of the megathrust during the 2011 Tohoku earthquake, caused by anomalously
high fluid pressure resulting from fluid accumulation over centuries.},
added-at = {2012-09-01T13:08:21.000+0200},
author = {Kimura, Gaku and Hina, Shoko and Hamada, Yohei and Kameda, Jun and Tsuji, Takeshi and Kinoshita, Masataka and Yamaguchi, Asuka},
biburl = {https://www.bibsonomy.org/bibtex/253037c7e1d0e7b5aebdb26b9b4305578/nilsma},
doi = {10.1016/j.epsl.2012.04.002},
interhash = {5cbfcd3d5a8dda1687030d6e014ff461},
intrahash = {53037c7e1d0e7b5aebdb26b9b4305578},
issn = {0012821X},
journal = {Earth and Planetary Science Letters},
keywords = {geophysics seismics seismology},
month = jul,
pages = {32--45},
timestamp = {2021-02-09T13:27:42.000+0100},
title = {Runaway slip to the trench due to rupture of highly pressurized megathrust
beneath the middle trench slope: The tsunamigenesis of the 2011 Tohoku
earthquake off the east coast of northern Japan},
url = {http://dx.doi.org/10.1016/j.epsl.2012.04.002},
volume = {339-340},
year = 2012
}