Building damage by the 2011 off the Pacific coast of Tohoku earthquake and coping activities by NILIM and BRI collaborated with the administration by Isao Nishiyama1, Izuru Okawa2, Hiroshi Fukuyama3 and Yasuo Okuda3 ABSTRACT structural steel buildings and reinforced concrete buildings is presented with typical damage This paper presents the outlines of the strong patterns observed also from the Quick Report. motions observed mainly by the Building The database on the damaged buildings subject Research Institute (BRI) Strong Motion Network, to tsunami which is compiled in the Quick the motion induced building damage and the Report is utilized to verify the tsunami load tsunami induced building damage by the 2011 defined in the Guidelines [1.3] for tsunami off the Pacific coast of Tohoku earthquake (the evacuation building made by the Cabinet Office. Great East Japan earthquake) (hereinafter referred to as the Tohoku earthquake). Coping In consideration of the building damage and so activities in order to establish necessary technical on by the Tohoku earthquake, “tsunami”, “non- standards by the National Institute for Land & structural elements”, “long-period earthquake Infrastructure Management (NILIM) and BRI ground motion” and “liquefaction” are important collaborated with the administration are also technical issues to be countermeasured by the outlined. administration. On these issues, the general outline of the coping activities by NILIM and As for the strong motions, it presents observed BRI collaborated with the administration motions at in and out of the buildings to show the utilizing the Grant-in-aid [1.4] for maintenance earthquake input and the response of the and promotion of building codes / standards is buildings. It also presents observations of the introduced. super high-rise buildings and the seismically isolated buildings under long-period earthquake KEYWORDS: Building Damage, Falling Down ground motions. Ministry of Land, Infrastructure of Ceilings, Liquefaction, Long-Period Ground Transport and Tourism (MLIT) and NILIM with Motion, Tsunami, 2011 off the Pacific Coast of the assistance of BRI released the Tentative New Tohoku Earthquake Proposal [1.1] for countermeasure against long- period earthquake ground motion on super high- rise buildings and seismically isolated buildings, whose general outline is also introduced. As for the motion induced building damage, it presents the general outline of the field survey on wood houses, structural steel buildings, reinforced concrete buildings, seismically isolated buildings and so on with the classified typical damage patterns for each structural systems based on the Quick Report [1.2], which does not give complete survey because of the 1 Director, Building Department, National Institute for widely damaged area affected by the Tohoku Land & Infrastructure Management (NILIM), Ministry of Land, Infrastructure, Transport & Tourism (MLIT), earthquake. Tsukuba-shi, Ibaraki-ken 305-0802, Japan. 2 Senior Research Fellow, Department of Structural As for the tsunami induced damage of buildings, Engineering, Building Research Institute (BRI), ditto. the general outline of damage of wood houses, 3 Chief Research Engineer, Department of Structural Engineering, BRI, ditto. 1 1. INTRODUCTION Ibaraki and Chiba Prefectures and Urayasu City on the Tokyo Bay, damage of residential land The Tohoku earthquake of moment magnitude associated with liquefaction was surveyed. (Mw) 9.0 occurred at 14:46 JST on March 11, 2011 and generated gigantic tsunami in the Tohoku and Kanto Areas of the northeastern part of Japan. This was a thrust earthquake occurring at the boundary between the North American and Pacific plates. This earthquake is the greatest in Japanese recorded history and the fourth largest in the world since 1900 according to U.S. Geological Survey [1.5]. An earthquake of Mw 7.5 foreshock preceded the main shock on March 9 and many large aftershocks followed including three Mw 7-class aftershocks on the same day of the main shock. As the epicentral distribution of the aftershocks of the Tohoku earthquake (hypocentral region) is widely located off the coast of the prefectures of Iwate, Miyagi, Fukushima and Ibaraki with approximately 450km in length in North-South direction and 150km in width in East-West direction. The distance from these prefectures to the fault plane is almost the same, thus the places Fig. 1.1 JMA Seismic Intensity Map with the seismic intensity of about 6 (6+ or 6-) according to the Japan Meteorological Agency (JMA) widely spread in these prefectures. The Tono City maximum JMA seismic intensity of 7 was Miyako City Yamada Town Kitakami City recorded by the strong motion recording network Otsuchi Town (K-NET) [1.6] of the National Research Institute Hiraizumi Town Kamaishi City Ohunato City Kurihara City for Earth Science and Disaster Prevention Rikuzentakata City Kesennuma City (NIED) at Kurihara City (K-NET Tsukidate) Minamisanriku Town shown by the purple color in Fig. 1.1, Miyagi Ishinomaki City Onagawa Town Prefecture, where the instrumental seismic Higashimatsushima City Matsushima Town intensity was 6.6. Shiogama City Shichigahama Town Tagajo City Sendai City Field survey by NILIM and BRI was started Natori City Iwanuma City from Kurihara City and was followed by the Watari Town Yamamoto Town Shiroishi Town locations shown in Fig. 1.2. In this paper, the Nasu Town Fukushima City Nihonmatsu City Yaita City results of the field survey at these locations are Miharu Town Koriyama City reported. In the coastal area from Aomori Shirosato Town Sukagawa City Kasama City Shirakawa City Hitachiota City Chikusei City Prefecture to Miyagi Prefecture, the tsunami Hitachi City Shimotsuma City Naka City induced building damage was mainly surveyed. Hitachinaka City Mito City Koga City Oarai Town The area facing to the Pacific Ocean in Bando City Omitama City Joso City Fukushima Prefecture was excluded from the Hokota City Tsuchiura City Kashima City Itako City Ryugasaki City Surveyed Cities and survey in the cause of the accident in Fukushima Kamisu City Towns Sakae Town Inashiki City Daiichi Nuclear Power Station. At the catchment Urayasu City basin area of Tone River in the border between Fig. 1.2 Locations of Surveyed Cities and Towns 2 These surveys were made from the viewpoint of damage such as collapse reported. finding whether there is something to reflect to current building structural codes or not. Namely, Strong motions are recorded in good quality are there new damage pattern in the motion during many large scale aftershocks in addition induced building damage? In case for tsunami to main shock and foreshock at in and out of the induced building damage, the technical buildings by the BRI Strong Motion Network information on the collapsed, overturned, washed and so on. Especially, they are valuable to see the away buildings are collected to verify the load characteristic of long-period earthquake ground effect by tsunami. As will be explained in the motion, which is thought to be strongly following chapters, the motion induced building generated and amplified in the occasion of huge damage is generally small and especially those earthquake, and to see the corresponding buildings which satisfy current seismic code after building responses. 1981 performed quite well with almost no severe 60,000 People injured People missing 50,000 People death 40,000 30,000 20,000 10,000 0 3/12 3/19 3/26 4/2 4/9 4/16 4/23 4/30 5/7 5/14 5/21 5/28 6/4 6/11 6/18 6/25 7/2 7/9 7/16 7/23 Kobe EQ (a) People death, missing and injured 500,000 450,000 Halfcollapsed (house) 400,000 Total collapsed include washed away (house) 350,000 300,000 250,000 200,000 150,000 100,000 50,000 0 3/12 3/19 3/26 4/2 4/9 4/16 4/23 4/30 5/7 5/14 5/21 5/28 6/4 6/11 6/18 6/25 7/2 7/9 7/16 7/23 Kobe EQ (housing units) (b) Total collapse and half collapse of houses Fig. 1.3 Progress of People Death (top) and Building Collapse (bottom) by the Tohoku Earthquake compared with those by Kobe Earthquake The statistical data on the people death and the Tohoku earthquake and “housing building collapse are announced from the units=household” for the Kobe earthquake, but it National Policy Agency [1.7] (August 15, 2011). can be said that “total collapse” and “half Fig. 1.3(a) shows the progress of people death collapse” are both almost half in the Tohoku which is compared to that in the 1995 Hyogoken earthquake. The Tohoku earthquake is much Nambu earthquake (Kobe earthquake), which larger than the Kobe earthquake and the affected shows that the number of people death in the area is far larger as a result, and also the washed Tohoku earthquake is almost 2.5 times as that in away houses are included in the total collapsed the Kobe earthquake. Fig. 1.3(b) shows the buildings. Thus, the motion induced building progress of building collapse which is again damage is far below in damage ratio than that in compared to that in Kobe earthquake. The unit of the Kobe earthquake. The Press Release [1.8] by the statistical data is different, “house” for the the Urban Bureau of MLIT showed that the total 3 collapsed houses in the tsunami inundation area structural elements such as ceiling, reached about 120,000, which is almost the same countermeasure for long-period earthquake number of total collapse by the National Policy ground motion on super high-rise buildings etc., Agency. This fact agrees well with the result by and countermeasure for liquefaction of the field survey. residential land. NILIM and BRI are cooperatively working on coping activities As the lessons from the Tohoku earthquake, the collaborated with the administration, which is following administrative issues are listed up: also introduced in this paper.