........ published in NEWSLETTER # 53
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........ published in NEWSLETTER # 53
ISSUES IN URBAN EARTHQUAKE RISK
by Dr. B.E. Tucker and Dr. C.N. Hwang, GeoHazards International, San Francisco (U.S.A.), and Dr. M. Erdik, Earthquake Research Institute, Istanbul (Turkey)
Urban seismic risk is growing worldwide and is increasingly a problem for developing countries. In 1950, one in four of the people living in the world's fifty largest cities was earthquake_threatened, while in the year 2000, about one in two will be. Further, of those people living in earthquake_threatened cities in 1950, about two in three were located in developing countries, while in the year 2000, about nine in ten will be. Unless urban seismic safety is improved, particularly in developing countries, future earthquakes will have ever more disastrous social and economic consequences.
The volume `Issues in Urban Earthquake Risk' (NATO ASI SERIES E271) consists of proceedings of the NATO Advanced Research Workshop on `An Evaluation of Guidelines for Developing Earthquake Damage Scenarios for Urban Areas'. The Advanced Research Workshop provided an opportunity for earthquake_threatened cities to compare hazard mitigation strategies and, where applicable, earthquake recovery experiences. Experts from both developed and developing countries attended the workshop, representing a broad range of specialities: Earthquake engineering, seismology, urban planning, emergency response, environmental management, and insurance. Of special consideration in preparedness planning was the use of an earthquake damage scenario (EDS), a description of the consequences to an urban area of a large, but foreseeable earthquake on the critical facilities of that area. Participants benefited from lessons learned in a recent pilot project in Quito, Ecuador, where an EDS was developed.
Several ingredients are the key to a successful EDS. First, a team effort is required, involving scientists, engineers, planners, government officials, and businessmen. Next, only the minimum necessary amount of technical information should be developed, according to available resources and the ultimate use of the results. Once developed, an EDS can be used to test the emergency response system and allow it to be improved, or to assist people concerned with post_earthquake reconstruction or pre_earthquake preparation. Several possibilities also exist for future EDS research, including the study of indirect losses and probability of the chosen earthquake; however, while EDS have proven useful to several of the participating cities, they are by no means the only solution.
The search for means to reduce the high vulnerabilities of urban areas in developing countries is particularly complicated by the scarcity of resources for preparation and mitigation activities, even in the wealthier communities. It is much easier to find funding for relief actions. Another common difficulty is the low level of awareness of earthquake risk among the general populace and city leaders.
The most striking observation from the reports at the Advanced Research Workshop is not the high seismic vulnerability of these cities or the difficulty of finding solutions, but the increase in most cities of seismic vulnerability over time. Only a few communities have long_term comprehensive programs to reduce their seismic risk; most cities have no risk reduction program. In order to be effective, such programs must reduce the risk factor faster than the natural forces _ such as urban growth _ are increasing it. The inevitability of earthquakes and the rapid population growth in earthquake_ prone urban centers worldwide make preparedness and risk reduction imperative. Preparation of an EDS is one important method of earthquake risk management.
Reference books: C74, C144, C266, E3, E271