Article,
Rupture process of the 2011 Tohoku-Oki mega-thrust earthquake (M9.0) inverted from strong-motion data
Geophysical Research Letters, (Oct 20, 2011)
DOI: 10.1029/2011GL049136
Abstract
We investigate the rupture process of the M9.0 Tohoku-Oki mega-thrust
earthquake using the relatively low-frequency strong-motion records
(0.01-0.125 Hz) observed at 36 K-NET and KiK-net stations, the epicentral
distances of which range from 120 km to 400 km. The fault model is
a rectangular plane, the length and width of which are 510 km along
the Japan Trench and 210 km along subducting direction of the Pacific
Plate, respectively. We perform the multi-time-window inversion analysis
with a 30x30 km2 subfault. The derived slip model has one large slip
area. This area extends from the region around the hypocenter to
the shallow part of the fault plane and further to the north and
south along the trench axis, located far off southern Iwate, Miyagi,
and northern Fukushima prefectures. The seismic moment is 4.42x10^22
Nm (Mw 9.0) and the maximum slip is 48 m. The slips near the coast
are relatively small, except off Miyagi prefecture, which experienced
a slip greater than 5 m. The shallow large slip area, which continuously
ruptured from 60 s to 100 s after the initial break, radiated seismic
waves rich in very-low-frequency content (< 0.02 Hz). The rupture
after 100 s propagating to the southern fault area, contributes to
the distinct phases observed for Fukushima and Ibaraki prefectures.
The relationship between the proposed rupture model and the feature
of the acceleration waveforms is not straightforward and suggests
the frequency dependency of the seismic wave radiation.
