Abstract
The source model of the 2011 Tohoku earthquake, which is composed of four strong motion generation areas (SMGAs), is estimated based on the broadband strong ground motion simulations in the frequency range 0.1–10 Hz using the empirical Green’s function method. Two strong motion generation areas are identified in the Miyagi-oki region west of the hypocenter. Another two strong motion generation areas are located in the Fukushima-oki region southwest of the hypocenter. The strong ground motions in the frequency range 0.1–10 Hz along the Pacific coast are mainly controlled by these SMGAs. All the strong motion generation areas exist in the deeper portion of the source fault plane. The stress drops of the four SMGAs range from 6.6 to 27.8 MPa, which are similar to estimations for past M 7-class events occurring in this region. Compared with the slip models and aftershock distributions of past interplate earthquakes in the Miyagi-oki and Fukushima-oki regions since the 1930s, the SMGAs of the 2011 Tohoku earthquake spatially correspond to the asperities of M 7-class events in 1930s. In terms of broadband strong ground motions, the 2011 Tohoku earthquake is not only a tsunamigenic event with a huge coseismic slip near the trench but is also a complex event simultaneously rupturing pre-existing asperities.
Highlights
The 2011 Tohoku earthquake, which occurred at 14:46 on March 11, 2011 (JST = UTC + 9), rocked over the Japanese country
All the strong motion generation areas exist in the deeper portion of the source fault plane
The source model composed of four strong motion generation areas of the 2011 Tohoku great subduction earthquake was estimated based on the broadband strong ground motion simulations using the empirical Green’s function method
Summary
In order to account for the observed strong ground motions of frequencies higher than 0.1 Hz, which are usually related to seismic damages on building and civil structures, constraints on the source process by higher frequency data are indispensable It is useful for such an analysis to use the records of small events occurring close to the target event as empirical Green’s functions. Some of the K-NET surface stations located at stiff soil and rock sites are used
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