Japan is subjected to frequent seismic activity. On January 17, 1995, the 1995 Hyogo-ken Nanbu Earthquake hit the Hanshin-Awaji region, a heavily populated area in western Japan. The Japan Meteorological Agency (JMA) reported that the magnitude was 7.2 and the epicenter was 16km underneath this region. About 6300 people died, and more than 150, 000 buildings were destroyed in and around the area with seismic intensity of VII, which is the highest level on the JMA scale. Reports on this earthquake disaster are extensive, such as the 10-volumes for building series edited by the Architectural Institute of Japan (AIJ) and the 12-volumes for civil engineering series edited by the Japan Society of Civil Engineering (JSCE), both series in Japanese. Here, based on these series edited by AIJ and JSCE, we give an overview of this earthquake, the related geological settlings, geotechnical conditions, strong ground motions, damage statistics, and structural damage to buildings, to infrastructures, to lifelines, and to other facilities such as associated mechanical equipment, elevators, and emergency power supply. Then, we report earthquake mitigation measures proposed by AIJ and JSCE based on lessons learned from this 1995 earthquake.

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After the Great Hanshin-Awaji Earthquake of 1995, the Headquarters for Earthquake Research Promotion was established as a special government organization. It has been promoting the following earthquake research:(1) creation of seismic hazard maps, (2) real-time transmission of earthquake information, (3) improvement of observation and other research in the areas and vicinities of intensified earthquake disaster prevention measures determined by the Special Measure Law on Earthquake Disaster Prevention, (4) improved observation and research for earthquake prediction.

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The Central Disaster Management Council (Chairman, the prime minister) is taking initiatives on planning basic schemes and promoting execution of disaster countermeasures in Japan. Recently, the council and the specialists committees, which are constituted under the council, carried out studies for the major subduction zone earthquakes along the Suruga and Nankai trough. The results are summarized and used for designation of the areas to strengthen and promote disaster management, damage estimation, and emergency response operations.

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The National Research Institute for Earth Science and Disaster Prevention (NIED) has carried on the special research project ‘National Seismic Hazard Mapping Project of Japan’ to support the preparation of the National Seismic Hazard Maps made by the Headquarters for Earthquake Research Promotion. In this article, the outline of methodologies to evaluate strong-motion both for the probabilistic seismic hazard maps and for the scenario seismic hazard maps is presented.

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The Strong-Motion Earthquake Observation Council is a consortium of many organizations involved in strong-motion observation in Japan. A short history and structure of the council is introduced along with the current activities of the council. Individual objectives and networks of strong motion observation of every organization are described in the following papers.

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After the 1995 Hyogoken-Nanbu earthquake, NIED (National Research Institute for Earth Science and Disaster Prevention) installed the K-NET that uniformly covers all Japan with more than one thousand strong-motion accelerometers on the ground surface. In addition to the K-NET, NIED constructed an uphole/downhole observation network, KiK-net, with approximately 669 stations. Each KiK-net station has a borehole of 100 m or more in depth and strong-motion seismographs have been installed both on the ground surface and at the bottom of the boreholes. The velocity profiles and geological information as well as the observed records are widely accessible on the website.

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The seismic intensity-meters over 3400 have been deployed by Japan Meteorological Agency (JMA) and local governments of all over Japan. These intensity data are utilized for quick earthquake information through all broadcasting in Japan. Most of seismic intensity-meters have capability to record and preserve the strong ground motion (acceleration). The high-level accelerations that had never observed before the installation were recently observed due to very dense sites.

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Strong ground motions and the response of structures have been observed in the major ports in Japan for more than 40 years. The network now covers the entire coastline of Japan with 110 accelerographs in 60 ports. This article describes the current status of the network, some findings from recent observations and data availability.

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Building Research Institute (BRI) is operating a nationwide strong motion network. Total 75 stations are disposed in major cities throughout Japan. The observation project aims to contribute to advance in seismic design technology for buildings. Therefore seismic response of buildings is the main target of the observation. A great number of strong motion records have been obtained and utilized to study local site and geological effects, soil-structure interaction and dynamic behavior of buildings. The paper introduces outline of the BRI strong motion network and its recent topics.

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The National Institute for Land and Infrastructure Management (NILIM) administers the observation of strong earthquake motion at more than 160 civil engineering structures throughout Japan, and dense instrument array strong earthquake motion observations at 98 sites in 9 areas. This paper describes current topics of strong earthquake motion observation at NILIM.

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The strong-motion observation system developed and maintained by the Earthquake Research Institute have focused on acquiring data from near earthquake sources and on studying local site effects on strong motion. The observation sites are mostly deployed between the Tokai and southern Kanto region, including the dense array in Ashigara valley.

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A large number of irrigation dams have been constructed in Japan. Strong earthquakes have often occurred and seismic observations in fill dams are very important for safety and countermeasures. Seismometers have been installed in 156 high irrigation dams since 1954 and seismic accelerations observed. Dynamic dam behavior is investigated by seismic observation records at the National Institute for Rural Engineering in cooperation with dam managers.

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Strong motion observation has been carried out on the rock outcrops by Central Research Institute of Electric Power Industry (CRIEPI) to obtain the basic data for the evaluation of design ground motions for electric power facilities. Now we operate 40 observatories deployed mainly in the southwestern Kanto district and the Izu Peninsula, Japan. We are preparing the strong-motion database open to the public by Internet, which will be accomplished within a couple of years.

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This paper gives a history of research and development concerning earthquake disaster prevention systems in Japan railways. Railway Technical Research Institute (RTRI) has established a new algorithm in evaluating quickly seismic source parameters (magnitude and epicenter location) from the initial part of P waves and developed a new earthquake quick alarm system (EQAS) which utilizes prompt earthquake information that will be provided by JMA.

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This paper presents the NTT and NTT FACILITIES earthquake observation system for earthquake resistant (low-rise, middle-rise, and high-rise building), vibration controlled, and base isolated buildings. The example of observation data of the Hyogo-ken Nanbu earthquake and the application of data for earthquake resistant design and shaking table test are described too.

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To cope with earthquake related secondary disasters, the new real-time disaster mitigation system for a city gas network has been developed by Tokyo Gas Company since 1998 for the purpose of realization of dense real-time seismic motion monitoring, quick gas supply shut-off, prompt emergency response and efficient restoration work. In 2001, Tokyo Gas successfully started the operation of SUPREME, which employs 3, 800 new SI sensors and remote control devices at all the district regulator stations in its service area (3100km²). SUPREME can observe the status of 3, 800 district regulators and shut them off remotely, if necessary. The remote shut-off using SUPREME can realize quick gas supply shut-off and effectively reduce gas leakage risk during earthquakes.

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This paper shows activity of CEORKA (The Committee of Earthquake Observation and Research in the Kansai Area) on observing strong ground motion records and providing the data. A quasi-real time data acquisition and broadcasting system of strong motion information is maintained by CEORKA. Members of the committee who supports the CEORKA project can receive seismic intensity map and waveform plots via E-mail, and can access automatically up-loaded digital files on home page (http://www.ceorka.org/).

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JMA is now developing Earthquake Early Warning system. In this issue, the methods used for prompt estimation of hypocenter locations, magnitude and seismic intensities, the warning dissemination criteria, and future plans are briefly introduced.

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The Tokai Earthquake currently expected to occur in the near future will be a great earthquake of magnitude 8. The damage caused by the Tokai Earthquake will be fairly intense. In addition, the damage will be extensive. For this reason, residents need to have a strong consciousness of “protecting one's own life” and “protecting one's community together”. In Shizuoka Prefecture, we have positively offered information concerning the basic geological data and the hazards associated with such a regional disaster so that residents can recognize the necessity to prepare earthquake countermeasures.

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A computer simulation system was developed to facilitate and enhance the engineering decision-making process for earthquake disasters. The present system provides an appropriate platform to examine vulnerability assessments of the water supply network, the road network within congested areas and the highway network. The database with GIS can store and sort complicated network data without difficulty; it enables engineers to comprehensively understand the evaluated results in an easily understood manner.

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The Great Hanshin-Awaji Earthquake gave critical damages to Kobe City. With the experience of Kobe City, Yokohama City has made full-scale review on the earthquake disaster prevention countermeasure plan. This paper reports earthquake disaster prevention activities based on scientific knowledge in Yokohama.

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This paper discusses the current status and future prospects of the residential earthquake insurance system in Japan. For about 40 years since its inception in 1966, the system has undergone many improvements based on lessons learned from past earthquakes: including the premium discounts taking into account the seismicresistance of buildings which were introduced after the 1995 Hyogoken-Nanbu Earthquake, the most challenging event the system has ever faced. Studies are also being conducted to establish a system that allows the insurance rates to be scientifically and effectively determined depending on risks. Earthquake insurances are expected to play a greater role in withstanding social and economic losses due to large seismic events that are predicted to occur in the future.

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The seismic design provisions of buildings in Japan was revised toward a performance-based structural engineering framework in 2000. The provisions provide two performance objectives: life safety and damage limitation of a building at two corresponding levels of earthquake motions. The design earthquake motions are defined in terms of the acceleration response spectra specified at the engineering bedrock to take account of the soil conditions and soil-structure interaction effects as properly as possible. The seismic performance shall be verified by comparing the predicted response values with the estimated limit values of a building.

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The Hyogo-ken-Nanbu (Kobe) Earthquake of January 17, 1995, caused destructive damage to the highway bridges. Based on the lessons learned from the Kobe Earthquake, the seismic design specifications for highway bridges were significantly revised in 1996. The intensive earthquake motion with a short distance from the inland-type earthquakes with Magnitude 7 class as the Kobe Earthquake has been considered in the seismic design. This paper summarizes the seismic design specifications for highway bridges after the 1995 Kobe Earthquake.

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The devastation wrought on railway structures by the 1995 Hyogoken-Nanbu earthquake has shown that there is an urgent need for developing a new seismic design of railway structures. After the earthquake, many groups set to investigate the reasons for the damage using static and dynamic analyses. This paper presents causes of seismically induced damage to bridges elucidated by some of these analyses of the earthquake, a contemporary seismic design method for railway structures, and issues related to the new seismic design method.

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As a result of the Kobe disaster in 1995, new analysis methods including the effective-stress analysis for quay walls and pushover analysis for pile-supported wharves are introduced in the technical standards for port and harbour facilities in Japan to assess seismic performance of structures beyond the limit of force balance. In this article, design practice of port structures in Japan is described, with focuses on these new analysis methods. Some of the problems to be solved are also briefly described.

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Seismic design of high-pressure gas facilities had been carried out in accordance with MITI notification 515 “Seismic Design Code” established in 1981. The Great Hyogoken-nanbu Earthquake occurred in 1995. Some facilities and piping systems were damaged due to ground displacement (settlement and/or lateral movement) induced by liquefaction. Having learned from the experiences, the seismic design code was amended in 1997. This paper introduces requirements in the new seismic design code and the evaluation method of Required Seismic Performance proposed.

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Following the 1995 Hyogoken-nambu (Kobe) earthquake, various integrated efforts have been directed toward upgrading seismic performance of vulnerable school buildings. In this paper, damage statistics of school buildings due to the Kobe earthquake, criteria to identify their vulnerability, the subsidy program for seismic rehabilitation, and their implementation examples, are briefly described, together with recent challenging efforts for further promotion of seismic rehabilitation on a nationwide basis.

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This paper presents the seismic retrofit practice of existing highway bridges in Japan. At first, the histories of the past seismic design codes, past seismic evaluation, and past seismic retrofit practices for highway bridges are described. Then the damage caused by the 1995 Hyogo-ken Nanbu Earthquake and the lessons learned from the earthquake are briefly described. Finally, the seismic retrofit program after the Hyogo-ken Nanbu Earthquake is described with emphasis on research and development as well as the seismic retrofit practice of existing reinforced concrete highway bridges.

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Seismic retrofitting of RC columns and piers of railway structures has been carried out since the Hyogo-Ken Nanbu Earthquake in 1995. This paper first describes a seismic retrofitting design flow of existing RC columns and piers of railway structures and secondly introduces representative seismic retrofitting methods.

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Japan has two decades of experience in designing and constructing baseisolated building structures. Construction has increased significantly since the 1995 Hyogoken-Nanbu (Kobe) earthquake, having reached over 150 annual construction projects. Many new developments and refinements have been made in the material, device, design, and construction of these structures. This paper summarizes recent design and construction of base-isolated building structures in Japan, including statistical data with respect to the common usage as well as the number of new projects.

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Twenty years have passed since response control systems, which reduce structural damages caused by earthquakes or strong winds, started to be used in actual buildings. JSCA conducted a survey of response-controlled buildings on design offices and construction companies, and made a database. Using this database a classification of the number of the buildings that use response control systems by the year of construction, the purposes of the building, and the type of mechanism device is performed. Also, the distribution of the applied damping forces and their response reduction efficiency are analyzed. Discussions of these analyses and of the present response control systems situation in Japan are finally reported in this paper.

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During the last two decades, active and semi-active control of civil engineering structures has made rapid progress in Japan. This technology has become widely used in earthquake engineering design, and more than 50 control systems have already been applied to buildings in Japan. The 1995 Hyogo-ken Nanbu Earthquake opened a door to positive development of semi-actively-controlled buildings against large earthquakes. This paper reports the state of the art by introducing practical applications, and describes future perspectives.

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This paper introduces the seismic isolation technology for highway bridges in Japan. Systematic application of seismic isolation was initiated in early 1990s. In particular it was accelerated after the 1995 Kobe earthquake. Guidelines and design specifications for seismic isolation are introduced. Typical implementation of seismic isolation to highway bridges are also presented.

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This paper outlines the latest status on seismic design for ITER in Japan, considering uniqueness in structure and safety features, and describes the associated on-going research for evaluation on tokamak dynamic response and verification tests using scaled tokamak model.

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A project has been undertaken in japan to develop three-dimensional (3D) seismic isolation systems for advanced fast reactors application, under the sponsorship of the japanese government. within this program, 3D base isolation systems with pneumatic and/or hydraulic devices are developed. A vertical isolation system with coned dish springs is also developed for reactor components with combined use of horizontal base isolation. This paper depicts a whole picture of the project and describes the current status of the development efforts.

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Research and practices on remedial measures for river dikes against soil liquefaction during earthquakes are presented. Though the river dikes have been constructed without rational seismic design but with empirical rules in their long history, intense urbanization to lowland behind dikes is demanding rationalization of the seismic design of river dikes. Geotechnical features of the foundation condition for dikes to fail, and the mechanism of dike failure are being revealed by what happened during the recent earthquakes in Japan. Advanced methods of estimating the earthquake-induced settlement of river dikes are also being developed in recent years. This paper attempts to compile the current trend of research direction and practices in Japan for strengthening the river dikes against earthquakes.

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Level-2 earthquakes such as the 1995 Kobe earthquake are defined scarce to occur during the lifespan of structures but necessary to consider by performance-based design. During the Level-2 earthquake, ground becomes more susceptible to liquefaction, resulting in larger settlement, uplifting and lateral spreading. With this back-ground in mind, the Committee for Liquefaction in the Level-2 Earthquake carried out data collections, sample analyses and made discussions based on them. Among major results obtained, the definition of liquefaction for Level-2 earthquake and case history studies on road bridge damage during level-2 Kobe earthquake are addressed.

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During the Kobe Earthquake in 1995, residential buildings and infrastructure were heavily damaged, and extensive liquefaction of ground was also observed. That triggered numerous hazard mitigation studies by gathering geotechnical and geographic information as well as damage records of the earthquake. Especially, processing such data has been making rapid progress, being reflected in mapping of liquefaction potential. This report describes a current state of the studies.

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It is well known that the port facilities in Kobe Port suffered severe damages during the 1995 Hyogoken-Nambu earthquake. Especially, many caisson type quay walls were damaged during the earthquake. In order to mitigate hazards and losses due to earthquakes, seismic design methodologies have been developed and revised after each past earthquake event. The design practice of port structures in Japan introduced a performance based design concept as a result of damage investigations after the 1995 Hyogoken-Nambu earthquake. The restoration of Kobe Port was based on following philosophies: 1) quick recovery of the functions of the port, 2) improve seismic performance, 3) renewal with change the function of facilities and 4) continued operation of the port during restore works.

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The liquefaction-induced ground flow inflicted serious damage to various engineered structures including highway bridges in the Kobe Earthquake of 1995. This paper summarizes the estimation of ground flow force acted on highway bridge foundations and the design technique developed to secure seismic safety of bridge foundations for liquefaction-induced ground flow, which was incorporated into the Design Specifications for Highway Bridges in Japan.

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Hanshin Expressway Public Corporation has struggled with the restoration and retrofit program for the foundations at Bay-shore Route since the 1995 Hyogoken-Nambu Earthquake. Damage to bored piles and their remediation work are overviewed here. Particularly some of the additional pile methods were discussed as one of the countermeasures against ground flow following the liquefaction.

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In Japan, studies on liquefaction-induced flow started just after the 1983 Nihonkai-chubu earthquake and were accelerated after the 1995 Hyogoken-nambu earthquake. Several prediction and countermeasure methods have been proposed. At Metropolitan Expressway, detailed study was conducted to evaluate the safety against the flow. Then, four sites were selected to reduce the effect of the flow by applying a countermeasure. The applied method was to install steel pipes between bridge foundations and sea walls.

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The Building Research Institute (BRI) launched a 5-year research and development project on Smart Materials and Structural Systems in 1998 as part of U.S.-Japan cooperative research efforts. Smart Structural Systems also called as Auto-adaptive Media are defined as systems that can automatically adjust structural characteristics, in response to the change by external disturbances and environments, toward structural safety and serviceability as well as the elongation of structural service life. Smart materials and systems have been developed and studied.

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The activities of the US-Japan Cooperative Research on Urban Earthquake Disaster Mitigation are described. The program was supported by the MEXT, Japanese government, and the NSF on the US side. Statements include motivations aroused by complex disasters in urban earthquakes, multi-disciplinary research framework, efforts for coordination, outputs and significant features of the program.

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The framework and major outputs from a multi-disciplinary, multi-lateral research project EqTAP are presented. Descriptions include motivations for the project, organizational scheme, objectives and research framework, outputs of the project, and innovative features of the EqTAP project. The outputs of the project are presented in terms of EqTAP Digital City/Tool Box, EqTAP risk management framework, and EqTAP case studies. The operating principles of EqTAP are also addressed where the “implementation strategies” is emphasized as their key concept.

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As a result of the Japan International Cooperation Agency (herein after referredto JICA) technological cooperation projects conducted by the Building Research Institute (herein after referred to BRI) in earthquake damage prevention researchand related areas since the 1980s, earthquake damage prevention research institutions have been founded in Indonesia, Peru, Mexico, Chile, Turkey, and on every other continent in the world. This paper provides a brief description of these projects, and discusses the issues which remain to be addressed in international technological cooperation in this area.

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The International Institute of Seismology and Earthquake Engineering (hereinafter referred to IISEE) of the Building Research Institute (hereinafter referred toBRI) has conducted the international training program for over 40 years and has received 1200 participants from about 90 countries. In this paper, history and present activities of the training courses are introduced, and its future will bediscussed.

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This paper introduces the outline of a research project on enhancement of earthquake performance of infrastructures based on investigation into fracturing process of structures. This project was sponsored by MEXT and managed by three institutions, JSCE, NIED and BRI. It was started in April 1999 and ended in March 2003.

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Densely populated urban cities that comprise a complicated web of people, urban facilities and urban system are highly vulnerable to earthquake disasters. Once an earthquake strikes such a metropolitan city, catastrophic disasters and widespread disaster chain, which may even lead to chaos in the global economy, can be anticipated. This has led to the pressing need for improving the overall earthquake risk reduction technology for urban cities. The Center for Urban Earthquake Engineering has been established to carry out the 21^st Century COE program entitled “Evolution of Urban Earthquake Engineering, ” that aims not only to promote the above research objectives but also to strengthen the graduate education program as well as to launch international collaboration in research and education. This paper describes the outline of our COE program on Urban Earthquake.

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