We report the investigation of the indoor damage and the questionnaire intensity for the high-rise university building in Tokyo during The Great East Japan Earthquake (Mw 9.0). The strong ground motions were observed around East Japan by this earthquake, the high-rise buildings experienced the unprecedented strong motions. However, this ground motions are smaller than the estimated scenario ground motions which are caused by Tokyo Metropolitan Earthquake and Tokai and Tonankai Earthquake, this earthquake caused the indoor damage to the high-rise buildings. Therefore, to get ready for the next great earthquake such as Tokyo Metropolitan Earthquake and Tokai and Tonankai Earthquake, we investigate our university high-rise building and correct the indoor damage and questionnaire survey.

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In order to evaluate the effects of surface soil structure and the amplification characteristics on the liquefaction damage in Mihama ward of Chiba city during the 2011 Great East Japan earthquake, microtremor measurement and seismic ground motion observation were conducted. The shear-wave profile models of divided 50m square grids in the ward were estimated based on lots of borehole logs. The equivalent linear analysis was conducted using the estimated profiles and the seismic ground motion record of the main shock. The distribution of estimated maximum shear strains of sand layers shows good agreement with the liquefaction damage distribution.

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The Onagawa Nuclear Power Plant, operated by Tohoku Electric Power Co., Inc., is situated near the focal region of the 2011 off the Pacific coast of Tohoku Earthquake. The array records observed at the site during the earthquake provide valuable information about the wave propagation at a large strain level. In this study, the temporal changes in the propagation velocities of the seismic waves were examined based on the vertical array records during the mainshock and the events before and after it. It was revealed that (1) the shear rigidity of the soil layers between sensors G-3 and G-4 (from G.L.-27.3 to -1.7 m) decreased by 60-70% at the maximum strain of 1×10^-3 due to the principal motion of the mainshock, whereas (2) the shear rigidity between sensors G-1 and G-2 (from G.L.-147.1 to -61.5 m) decreased only by 10-20% at the maximum shear strain of 5×10^-5.

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This paper presents the damage situation of telecommunication infrastructure facilities of Nippon Telegraph and Telephone CORP. due to the Great East Japan Earthquake. The analysis on tendency of suffered damages and the examination on validity of the earthquake-proof measures implemented so far are also reported. In comparison with the Kobe earthquake, it turned out that damage ratio of facilities due to earthquake motion and ground deformation, except tsunami damage, which occurred by the Great East Japan Earthquake was smaller. Moreover, we examined the possibility to detect weak points using the ground information currently released, supposing a metropolitan epicentral earthquake and the Tokai, Tonankai and Nankai earthquake.

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The M_w 9.0 destructive earthquake that occurred March 11, 2011, in Japan was associated with widespread liquefaction within a 650-km long zone that extended from Aomori to Kanagawa Prefectures in the eastern part of Japan. Based on reconnaissance surveys of the Great East Japan Earthquake of March 11, 2011, recurrence of liquefaction at the same sites was identified at 85 sites where liquefaction had occurred during the previous earthquakes such as the Chibaken toho-oki earthquake of December 17, 1987 and the Miyagiken-oki earthquake of June 16, 1978; the surveys also compared observed liquefaction effects with those of the previous earthquakes.

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Strong quake and the associated tsunami due to the 2011 off the Pacific coast of Tohoku Earthquake resulted in huge damage to many earth structures. A lot of coastal protection structures suffered heavy casualties due mainly to the erosion. However, the degree of damage to the river levees and embankments were different depending on the topography and the structural form. The main objective of this study is to collect basic information related to the seismic resistant and tsunami resistant characteristics of earth structures. To that end, site investigations and laboratory soil investigations on earth structures were performed at two locations of the central and southern part of Iwate prefecture. The investigation results show that subsidence related failure probably had taken place in the body of covered embankment with low penetration resistance and high water table. On the other hand, in the case of retaining wall made of tires, due to flexibility and ductility of the tires and the hoop tension that prevails within each individual tire prevented the wall from any damage due to erosion and the impact forces of tsunami.

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We evaluated the characteristics of earthquake ground motions and site amplification factors for periods more than 2 seconds in the Tokyo Metropolitan Area and its vicinity, by the main shock and aftershocks of the 2011 off the Pacific coast of Tohoku Earthquake. The complex distribution of earthquake ground motions by PGV and PGA in the Tokyo Metropolitan Area were shown, using recording data of the main shock observed at seismic stations of about 650. Also, the pseudo velocity responses for periods of 2 and 3 seconds in Kawasaki to Shinagawa were extremely large. Site amplification factors, which were estimated by the ratio of velocity response spectra on surface to those in the seismic bed rock, have the azimuthal dependence to epicenter for periods more than 3 seconds. Long-period ground motions in the Tokyo Metropolitan Area were more largely amplified by earthquakes located in Northern Nagano Pref. and Eastern Shizuoka Pref. than those located in Tohoku Region.

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This paper describes the amplitude dependent dynamic characteristics of a 9 story building in Sendai before, during, and after the 2011 Tohoku earthquake. Dynamic hysteresis characteristics are investigated based on actual observation records. Occurrence of partial uplifting in the transverse direction is suggested by the induced higher harmonics based on the wavelet analysis. The suggested phenomena are consistent with the damage features. Historical change of the dynamic characteristics is also discussed based on the long-term monitoring data.

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Currently used Japanese seismic intensity based on measurement value by mechanical instrumentation, which is called measurement seismic intensity and not always affects human body feeling and earthquake damage. The measurement seismic intensity represents local ground motion characteristics at an observation point due to the foundation and geology conditions and is difficult to evaluate the seismic intensity at a point between observation points. The questionnaire seismic intensity can be said to be very effective in the point. Therefore, in this research, the questionnaire survey to investigate areal ground motion characteristics in two cities in Miyagi prefecture during the 2011 off the Pacific coast of Tohoku Earthquake and its one of aftershocks on April 7, 2011. One is Ohsaki city of which central area was suffered from serious damage in the main shock. The other is Kurihara city including the Tsukidate area where serious damage in the main shock. The other is Kurihara city including the Tsukidate area where serious damage was not recognized even if the seismic intensity scale was 7 during the main shock.

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Significant liquefaction affected the Tonegawa basin as well as the Tokyo-bay area during the 2011 Tohoku-oki earthquake. This liquefaction caused undermining many house foundations and destroying infrastructure around these areas. In this report, we focus on the pattern of liquefaction in the Tonegawa basin and the probability of liquefaction occurrence in Kanto district during the 2011 Tohoku-oki earthquake. First we revealed the liquefaction pattern in the Tonegawa basin based on the field survey at 29 municipalities in Chiba and Ibaraki prefectures. The evidences of liquefaction were mainly found in the artificial ground created from the sea, pond, and river. Second we calculate the probability of liquefaction occurrence during the 2011 Tohoku-oki earthquake for each geomorphologic classification unit in whole Kanto district according to a variety of survey results including our own. The liquefaction probabilities of the 2011 Tohoku-oki earthquake are much larger than those of past earthquakes caused liquefaction.

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As a result of the 2011 Great East Japan Earthquake, five slope failures occurred in a residential area on artificial valley fills in Taiyo New Town, Yamamoto, Miyagi Prefecture. The site was constructed by leveling the hilly area and using the cut materials as fills for the valleys to provide foundation ground for houses. The fill material is sandy, derived from the weathering of tuffaceous sandstone which formed the natural ground. Each of the five slope failures was observed to occur at the boundary between the filled-up valley and the fill or on the shoulder of the embankment. The sandy fill material has a fines content of F_c=20%. Even when compacted at 90% degree of compaction, the fill material showed a very low internal friction angle and low cyclic shear strength. Moreover, the cyclic shear strength decreased with application of initial shear stress. Pseudostatic slope stability analysis using conventional strength parameters could not explain the slope failure, however it could when the dynamic strength was used to represent the soil strength at the slip surface. Thus, the slope failure in Taiyo New Town can be attributed to cyclic shear failure of the fill material induced by intense shaking.

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On March 11, 2011, after the occurrence of the 2011 off the Pacific coast of Tohoku Earthquake, the operation of railway system in Tokyo metropolitan was suspended for a long time so that huge number of people got into difficulties in moving. Meanwhile, some people began returning home under the situation whether he/she can return home safely. Furthermore, some people put himself/herself in unsafe situation by spending night in the open air. To clarify the situation when the people had begun returning home is significant in order to consider the measures to Tokyo metropolitan inland earthquake which is expected to occur in near future.
Therefore, the timing when the people started returning home was focused in this study. An internet survey was conducted to collect the data regarding the behavior of the people who had difficulties in moving on the day. Moreover, the data regarding the restart time of railway operation was collected from railway companies.
It is confirmed that the most people started returning home before the railway service on the way had not been fully restored and that success rate of returning home for the people who did not use railway service was relatively low.

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The characteristics of long-period ground motion of Tokyo bay area were studied using the records of the 2011off the Pacific coast of Tohoku earthquake, foreshock and aftershocks. The long-period pulse with period about 20 seconds is significant in velocity seismograms and displacement seismograms of main shock. There is no significant peak in the velocity response spectrum of main shock between 5 to 10 seconds. The velocity response spectra of foreshock and aftershocks located in Miyagi-oki and Ibaraki-oki area also have no significant peak. On the other hand, the spectra of the event located in northern Nagano area have significant peak in periods of 5 to 7 seconds. The excitation of long-period ground motion is different in accordance with the epicenter regions. The phase velocities in period range between 7 to 8 seconds evaluated from the 2011 off the Pacific coast of Tohoku earthquake are faster than those of the 2007 Niigataken Chuetsu-Oki earthquake. Long-period ground motions were excited in Tokyo metropolitan area during the 2007 Niigataken Chuetsu-Oki earthquake. This result suggests that the incident wave field has a relation to the excitation of long-period ground motions.

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Focusing on a three storied RC Building which was damaged by 2011 Tohoku Earthquake, we examined its modal properties by analyzing both acceleration records of the main shock and microtremor records observed after the earthquake. The damaged stories were detected from the identified natural modes from the microtremor records. In addition, we estimated the modal parameters by two kinds of frequency domain decomposition technique; one for general viscous damping system, the other for proportional damping system. The influence of viscous damping condition on the identified natural modes was discussed.

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Modal parameters of a building damaged heavily by the 2011 off the Pacific coast of Tohoku Earthquake were identified from ambient vibration data with frequency domain decomposition techniques (FDDT). The characteristics of the identified 3-D mode shapes were discussed with respect to the earthquake damages. Also, we identified the mode shapes by two kinds of FDDT; one for general viscous damping system, the other for proportional damping system. The influence of viscous damping condition on the identified mode shapes was discussed.

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