17:15 〜 17:30
[SSS01-12] Earthquake mechanism in post-megathrust intraplate stress
キーワード：stress shadow, intraplate, megathrust, long-term evolution, Korean Peninsula
Megathrusts produce large permanent lithospheric
displacements as well as strong transient ground shaking
up to regional distances. The lateral permanent
displacements construct stress shadows in a wide backarc
region. The Korean Peninsula is placed in the far-eastern
Eurasian plate that belongs to a stable intraplate region
with a low earthquake occurrence rate and diffused
seismicity, and is located in the backarc at ~1300
km in the west from the epicenter of the 11 March 2011
M9.0 Tohoku-Oki earthquake. The seismicity around the
Korean Peninsula was increased significantly after the
2011 M9.0 Tohoku-Oki earthquake, which is not consistent
with the expected seismic-quiescence. Strong seismic
waves cause large dynamic stress changes, incurring fluid
migration and increasing pore fluid pressure in the
media. The lithospheric displacements directing to the
epicenter on the convergent plate boundary develop
transient radial tension field over the backarc
lithospheres, which is subparallel with the preseismic
ambient compressional field. The pore pressure growth and
radial tension field decrease the Coulomb failure stress,
increasing episodic increases of seismicity in both fault
zones and intact media. The ambient stress field is
recovered gradually as the induced stress field
diminishes with time by tectonic loading. The seismicity
changes with the temporal evolution of stress field. A
series of moderate-size earthquakes and earthquake swarms
occur as a consequence of medium response to the temporal
evolution of stress field. The long-term evolution of
seismicity is expected to continue until the preseismic
ambient stress field is fully recovered.
displacements as well as strong transient ground shaking
up to regional distances. The lateral permanent
displacements construct stress shadows in a wide backarc
region. The Korean Peninsula is placed in the far-eastern
Eurasian plate that belongs to a stable intraplate region
with a low earthquake occurrence rate and diffused
seismicity, and is located in the backarc at ~1300
km in the west from the epicenter of the 11 March 2011
M9.0 Tohoku-Oki earthquake. The seismicity around the
Korean Peninsula was increased significantly after the
2011 M9.0 Tohoku-Oki earthquake, which is not consistent
with the expected seismic-quiescence. Strong seismic
waves cause large dynamic stress changes, incurring fluid
migration and increasing pore fluid pressure in the
media. The lithospheric displacements directing to the
epicenter on the convergent plate boundary develop
transient radial tension field over the backarc
lithospheres, which is subparallel with the preseismic
ambient compressional field. The pore pressure growth and
radial tension field decrease the Coulomb failure stress,
increasing episodic increases of seismicity in both fault
zones and intact media. The ambient stress field is
recovered gradually as the induced stress field
diminishes with time by tectonic loading. The seismicity
changes with the temporal evolution of stress field. A
series of moderate-size earthquakes and earthquake swarms
occur as a consequence of medium response to the temporal
evolution of stress field. The long-term evolution of
seismicity is expected to continue until the preseismic
ambient stress field is fully recovered.