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We revise the empirical relations for acceleration response spectra and average and variance of group delay time of long-period ground motions. The MW2 term is added in the revised relation for response spectra. In addition the differences between the Pacific plate earthquakes and the Philippine Sea plate earthquakes are considered into their attenuation and the site coefficients. We set the three-connected source model composed of three outer-faults based on strong motion generation areas of the Tohoku earthquake. Finally we show that the long-period strong motions of the Tohoku earthquake are reasonably simulated well using the revised attenuation relations and the three-connected source model.
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The 2011 earthquake in Tohoku, Japan caused extensive liquefaction in the coastal area of the Tokyo Bay and the lower banks of the Tone River in the North Kanto region. Because small-diameter underground pipelines were subjected to ground deformation, the amount of pipeline damage can be considered an indicator of the severity of the liquefaction. An analysis of the pipeline damage in the Kashima region along the lower banks of the Tone River showed that the damage was concentrated in an area of 1 km2 . In this study, the reason for the concentration of damage in that small area was analyzed with respect to landform and land use changes that had occurred. The area in which the pipeline damage was concentrated was identified using old topographic maps compiled in the 1880s, as it was difficult to identify the area of concentrated pipeline damage using the current topographic map alone.
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This presents a newly developed source model, composed of super asperities, for the 2011 off the Pacific coast of Tohoku, Japan, earthquake. Strong ground motions were simulated based on site amplification and phase characteristics. The constructed source model involves 9 super asperities, located off the coast of Miyagi through Ibaraki. There was good agreement between the observed and calculated ground motions, especially for the velocity waveforms (0.2-1.0 Hz) including near-source pulses.
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In this paper, according to the survey, it was able to grasp reality of high-rise building-specific damage that occurred at the Great East Japan Earthquake (“the 3.11 Earthquake”), initial response of regional businesses, and support to the people who were unable to return home. In addition, we clarified the future issues learned from the actual situation and proposed efforts to enhance disaster prevention in cooperation with the local communities to minimize the disruption of a large-scale earthquake.
Released: December 19, 2014
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Many aftershocks were observed in the Pacific coast of Tohoku Earthquake. In view of this fact, aftershocks should be paid attention, although it is ignored in conventional design. In this paper, the effect of aftershocks to buildings is discussed focusing on energy input. From cumulative energy spectrum, it is elucidated that aftershocks recorded this time have enough energy to bring certain level of damage. P-delta effect degrades the strength of the buildings. Therefore, buildings damaged after main shock can be brought significant incremental deformation by small energy of aftershocks.
Released: December 19, 2014
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Strong ground motions in the frequency range of 0.2-1 Hz observed along the east coast of Tohoku, Japan, from Miyagi to Ibaraki during the 2011 Tohoku earthquake are characterized by distinct pulses. The generation of such pulses is significantly important especially in the context of seismic design of structures. In this article, examples of strong-motion pulses from huge subduction earthquakes are presented and the relationships between the parameters of the SPGAs (Strong-motion Pulse Generation Areas) and the moment magnitude of the earthquakes are investigated.
Released: December 19, 2014
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In the Great East Japan (Tohoku) Earthquake which occurred on March 11, 2011, strong ground motions were observed in an extensive area from the Tohoku regions to the Kanto region with unprecedentedly strong tremors felt at high-rise buildings located in the Tokyo metropolitan area. However, because the shaking of the earthquake observed in the Tokyo metropolitan area was smaller than the estimated scenario ground motions caused by earthquakes occurring directly beneath the area and the Tokai-Tonankai earthquake, those estimated earthquakes may cause major damages in the area. In order to reduce such damages, this report aims at outlining ground motions and damages of a high-rise building caused by the Great East Japan Earthquake, and at being of use in taking measures of seismic disasters. For this purpose, this report investigates a record of observation and damages caused on the day of the earthquake, a survey conducted after the earthquake with the focus on the high-rise building of the campus of Kogakuin University located in the Tokyo metropolitan area.
Released: December 19, 2014
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We investigated the strong ground motions and the damage of buildings near the coseismic surface faulting of the 2011/04/11 Fukushima-ken-Hama-Dori Earthquake (the April 2011 Fukushima earthquake, Mw 6.6). First, we confirmed that the ground motions from this normal fault were equivalent and/or stronger than the thrust fault, by comparing the strong motion records with the attenuation relation. We also checked that the ground motions near the epicentral area were larger than those of the 2011/03/11 Great Tohoku earthquake (Mw 9.0). Therefore, the most of building damage was probably caused by the 2011 April Fukushima earthquake. Next, we investigated that the 191 buildings near the surface faulting (within 500 m), and obtained the following conclusions. The most of severe damage was caused by the surface faulting and the subsequent ground failure. Among 9 buildings above the surface faulting, only one building was overturned; the building was a traditional tall gate in a Budhism temple, and fell on the side by the surface faulting of about 60 cm dislocation, because the columns were not anchored to the foundations. As for the other buildings, the damage by the strong ground motion was negligible. That is, the rate of heavy damage (Damage Grade 4 and upper) was less than 2%, which corresponds to JMA Intensity 5- and 6+, even though the most of buildings seemed very old and weak.
