The Great East Japan Earthquake Damage Report
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BUILDING RESEARCH INSTITUTE The Great East Japan Earthquake Damage Report The Building Research Institute of Japan has conducted an extensive survey of the damage caused to buildings and homes by seismic motion and tsunami waves during the 2011 Great East Japan Earthquake, and offers this report. (Detailed data including damage due to tsunami: http://www.kenken.go.jp/english/ index.html) To obtain technical Figure 1: Distribution of slip amount data to be used in a re- on the fault estimated from tsunami view of technical stan- measurements (Fujii et al:, 2011, dards in light of the Earth, Planets and Space) earthquake, after the earthquake struck the Building Research Institute (BRI) and the National Institute for Land and Infrastructure Management (NILIM) set about the task of collecting information on damages due to seis- mic movement and the tsunami waves, focus- The tsunami swept away all the wooden and low-rise build- ing primarily on build- ings in this coastal area of Onagawa, Miyagi Prefecture, ing structures. except for a solitary reinforced concrete building. The shaking expe- rienced around the t 2:46 p.m. on March 11, country is important information through 2011, what is formally known which we can understand the structural as the “2011 off the Pacific damage caused by the earthquake. To A coast of Tohoku Earthquake” look at this, we will introduce strong mo- struck, with an epicenter off the coast of tion seismograms recorded in the disas- Sanriku. Casualties from the disaster ter-affected regions, which were obtained stand at 15,839 fatalities and 3,642 miss- through the strong-motion earthquake area from Hokkaido to western Japan. ing. Damage to buildings includes observation project conducted by the As the earthquake occurred along what 120,241 buildings completely destroyed, BRI. The epicentral area of this earth- is known as a plate boundary, the rup- 189,822 buildings partially destroyed quake was extremely large, and regions tured epicentral area was large, and the and 598,587 buildings partially damaged experiencing strong motion occurred resultant aftershock area is estimated to (announced by the National Police across the widest area ever seen. have been around 500 km to the north Agency as of November 17, 2011). While buildings also suffered dam- and south, and around 200 km to the While the size of the earthquake age, buildings constructed according to east and west. The seismic rupture was reported as magnitude 7.9 by the the new earthquake resistance standards began around the area indicated by the Japan Meteorological Agency immedi- did not suffer major damage. In light of symbol in Figure 1, and according to ately after it struck, on March 13 this lessons learned from earthquake damage BRI analysis, the largest slip amount of was revised to 9.0 (on the moment mag- due to the 1978 Miyagi earthquake and about 48 meters occurred in the vicinity nitude scale). An earthquake of this size others, Japan strengthened its seismic of the ocean trench where the plate was Japan’s largest in recorded history, design standards in accordance with the boundary is located. It is also estimated and the scale of damage it caused was Building Standards Law and related that between 10 and 30 meters of slip also greater than ever experienced. ordinances from June 1981. These stan- amount occurred from off the coast of The tsunami waves that arrived dards are known as the new earthquake Miyagi Prefecture to the southern along the coast shortly after the earth- resistance standards. Sanriku Coast, approximately ten meters quake hit reached far inland over a vast off the Fukushima coast and roughly area from Aomori Prefecture in the Large Epicentral Area two meters off the coast of Ibaraki north to Chiba Prefecture in the south, Prefecture. Off the central Sanriku coast, resulting in immense damage. The earthquake was felt across a wide slip amount of between five and eleven 22 The Japan Journal DECEMBER 2011 The Japan Journal DECEMBER 2011 23 Figure 2: Distribution of seismic Figure 3: Records obtained from BRI Figure 4: BRI strong motion observation intensity for each region during the strong motion observation stations stations in the Tokyo metropolitan area main shock meters is estimated in some areas. were felt across almost all of Japan. the building at the time. This is easy if The symbol in Figure 1 indicates the seismic observations are conducted in *1 K-NET: A ground-based strong-motion starting point of the rupture which rep- earthquake observation network installed buildings. The BRI conducts seismic resents the beginning of the earthquake. across Japan by the National Research observations targeting buildings at ap- From this point the rupture widened as Institute for Earth Science and Disaster proximately seventy locations nation- Prevention and the system which transmits far as off the coast of Iwate Prefecture to strong-motion recording data via the Internet. wide with the aim of measuring the the north and Ibaraki Prefecture to the *2 Gal: Unit of acceleration (1 gal earthquake resistance of buildings. south, resulting in a vast epicentral area. = 1 cm/s2) Figure 6: Characteristics of seismic movements Widespread Shaking The seismic intensity in disaster-affected regions (inside buildings). readings shown in Figure 2 The stated level is exceeded at 2 and 3 seconds In Japan, the size of earthquake shocks is are calculated from ground- into the cycle, but this is not a problematic level. expressed in terms of the Japan based observation records. Damping Ratio: 5% Akita Prefectural Office B1F Meteorological Agency (JMA) Seismic Seismic movements vary not Hachinohe City Hall GL Iwaki City Hall B1F Intensity Scale. The largest seismic inten- only according to the size of Miyako City Hall GL Niigata City Hall B1F sity recorded during the 2011 earthquake an earthquake and the dis- Sendai Government Office Building B2F Design Level on Bedrock was level 7 at the Tsukidate station in tance from the epicenter, but Kurihara, Miyagi Prefecture. No other also due to ground conditions areas recorded level 7 intensity. at the observation point. However, in terms of peak ground accel- To determine whether a (cm/s) eration, which is an alternate indicator of building is resistant to earth- shaking used by strong motion observa- quakes, it is important to de- tion networks operated by other agencies termine not only the response such as K-NET*1, this measurement sur- of the building during an Response Pseudo Velocity passed 1,000 Gal*2 at many observation earthquake, but the seismic Period (seconds) stations. As Figure 2 shows, the shocks motions which acted upon Figure 7: Seismic motion characteristics at obser- vation stations in the Tokyo metropolitan area Figure 5: Comparison of observed waveforms (velocity waveforms) (first floors, basement floors or ground surface) for the same building during the 1978 Earthquake off the Coast of Educational Center, Funabashi City GL Miyagi Prefecture (blue) and the 2011 Earthquake off the Pacific Damping Ratio: 5% Gyotoku Library, Ichikawa City 01F Central Government Building No. 6 01F coast of Tohoku (black) Sumida Ward Office B1F 37-story High-rise Residential Building, Chuo Ward 01F June 12, 1978 Off the Coast of Shinagawa International House, Tokyo University Miyagi Prefecture Earthquake of Marine Science and Technology Design Level on Bedrock (cm/s) Velocity (cm/s) Velocity March 11, 2011 Off the Pacific Coast of Tohoku Earthquake Pseudo Velocity Response Pseudo Velocity Time (seconds) Period (seconds) 22 The Japan Journal DECEMBER 2011 The Japan Journal DECEMBER 2011 23 BUILDING RESEARCH INSTITUTE Table 1: Main strong motion records obtained by BRI was large, and since there was a long time Max. Acc. (cm/s2) from the start to end of rupturing at the Code Station Name _ (km) IJMA Loc. H1 H2 V epicenter, the shocks felt in all regions Sendai Government Office B2F* 163 259 147 SND 175 5.2 continued for longer than ever before. Bldg. No. 2 (high-rise) 15F 361 346 543 Table 1 shows the instrumental inten- 01F* 333 330 257 Tohoku University Civil Engineering and THU 177 5.6 sity, directional peak acceleration, etc. of Architecture Bldg. 09F 908 728 640 the shocks recorded at major observation 01F 138 122 277 stations during the 2011 earthquake. MYK Miyako City Hall 188 4.8 07F 246 197 359 Of these stations, the Civil GL* 174 174 240 B1F* 175 176 147 Engineering and Architecture building IWK Iwaki City Hall 210 5.3 09F 579 449 260 (ninth floor) at Tohoku University, A01* 279 227 248 which recorded a large velocity response A89 142 153 102 during the 1978 off the coast of Miyagi BFE 194 191 136 ANX Building Research Institute 330 5.3 8FE 597 506 344 Prefecture earthquake, also obtained a MBC 203 206 152 large recording this time. However, M8C 682 585 311 from the comparison of their respective B3F* 74 63 42 Figure 5 Saitama Shintoshin Government velocity waveforms shown in SIT2 378 4.4 10FS 119 138 62 Office Building No.2 Annex (high-rise) we can see that the 2011 earthquake was 27FS 248 503 107 much longer than the 1978 earthquake. Saitama Shintoshin SITA Government Office Building, Public 378 4.5 01F* 90 105 47 In Figure 6, we compared the pseudo Welfare Building velocity response spectra that indicates GL* 265 194 150 the cyclical size of seismic motions for National Museum of Western Art B1FW 100 79 84 NMW 382 4.8 (base-isolation) 01FW 76 89 87 buildings in the main disaster-affected 04F 100 77 90 regions of Sendai, Iwaki, Miyako and 01F* 90 86 45 Central Government Office Bldg. No.6 Hachinohe.