4:45 PM - 5:00 PM
[S13-4-02] Eccentric by-players of the 2011 Mw 9.1 Tohoku earthquake
We analyzed the low rate GPS displacement records of GEONET and the continuous stress record at TOS of TRIES (about 600 km away in an azimuth of N120W) due to the 2011 Tohoku earthquake. This led us to a recognition of the tree eccentric by-players as below.
(1) Super sub-event of Mw8.4
We perceived a dominant single SH pulse of a width of around 30 s propagating with 3.9 km/s to stations of epicentric distances of hundreds of kilometers in record sections of a transverse component of the records. The SH pulse can not be elucidated by subfault/asperity of low angle thrusting along the subduction interface. Matching synthetic waveforms in a half space to the SH pulse in trial and error approach, we obtained a extraordinary subfault model in which slip velocity and seismic moment were around 10 m/s and (4-5)**21 Nm (Mw 8.4), with strike direction N145E, dip angle 85 and slip angle 85, while a slip and an area of faulting cannot be separately solved because of a trade-off between them.
(2) Hyper-resonance
At stations in the southern part of the Boso peninsular in azimuths of N145W to N150W, we saw a remarkable resonance of few cycles of SH waves of periods of 15 s to 20 s and amplitude of up to 1 m following the SH pulse, which we call hyper-resonance. It can be attributed to thick tertiary accretional layer.
(3) Dynamic trigger
Giant near-source seismic waves triggered activity of M6 or larger aftershocks in the source area. Those of a few hundred kPa triggered aftershock activity at active volcanoes such as Tateyama and Yakedake in the Hida mountains. These aftershock activity lowered around 50 minutes after the main shock. After one and half hours, two and half hours and three hours, the higher mode Rayleigh waves, the fundamental Love waves and the Rayleigh waves, respectively, of 200 s to 300 s of a few kPa returned back to Japanese Islands. They reactivated the aftershock activity.
(1) Super sub-event of Mw8.4
We perceived a dominant single SH pulse of a width of around 30 s propagating with 3.9 km/s to stations of epicentric distances of hundreds of kilometers in record sections of a transverse component of the records. The SH pulse can not be elucidated by subfault/asperity of low angle thrusting along the subduction interface. Matching synthetic waveforms in a half space to the SH pulse in trial and error approach, we obtained a extraordinary subfault model in which slip velocity and seismic moment were around 10 m/s and (4-5)**21 Nm (Mw 8.4), with strike direction N145E, dip angle 85 and slip angle 85, while a slip and an area of faulting cannot be separately solved because of a trade-off between them.
(2) Hyper-resonance
At stations in the southern part of the Boso peninsular in azimuths of N145W to N150W, we saw a remarkable resonance of few cycles of SH waves of periods of 15 s to 20 s and amplitude of up to 1 m following the SH pulse, which we call hyper-resonance. It can be attributed to thick tertiary accretional layer.
(3) Dynamic trigger
Giant near-source seismic waves triggered activity of M6 or larger aftershocks in the source area. Those of a few hundred kPa triggered aftershock activity at active volcanoes such as Tateyama and Yakedake in the Hida mountains. These aftershock activity lowered around 50 minutes after the main shock. After one and half hours, two and half hours and three hours, the higher mode Rayleigh waves, the fundamental Love waves and the Rayleigh waves, respectively, of 200 s to 300 s of a few kPa returned back to Japanese Islands. They reactivated the aftershock activity.