[S-SS03] Induced and triggered seismicity: case-studies, monitoring and modeling techniques

[SSS03-04] Aftermath of a regional megathrust earthquake on crustal perturbation and induced seismicity

*Tae-Kyung Hong¹, Junhyung Lee¹, Seongjun Park¹ (1.Department of Earth System Sciences, Yonsei University)

Megathrust earthquakes 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. 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. The seismic velocities in the crust were
decreased after the megathrust earthquake, which
recovered gradually with time for several years. A series
of moderate-sized 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 ambient
stress field is fully recovered.