Kobe Earthquake

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             Differences in Kobe and Northridge .
             While there are more similarities than differences in structural performance in the Kobe and Northridge earthquakes, there are important differences that explain why the Kobe Earthquake was so much more damaging. Some of the lessons from these differences apply only to Japan, others apply to all areas of the world at risk from earthquakes. .
             The vast majority of deaths in Kobe occurred in the collapse of housing built using traditional Japanese methods. Traditional Japanese housing construction is based on a post-and-beam method with little lateral resistance. Exacerbating the problem is the practice of using thick mud and heavy tile for roofing, resulting in a structure with a very heavy roof and little resistance to the horizontal forces of earthquakes. U.S.-style frame housing with light-weight roofs is now coming into use in Japan and newer housing constructed using these methods had little or no damage from the earthquake. .
             Another significant difference between the Kobe area and the Northridge area is the quality of the soils. Because of a severe shortage of available land, much of modern urban Japan, including Tokyo, is built on the worst soil possible for earthquakes. Much of the newer construction in Kobe, particularly larger buildings, is built on very soft, recent alluvial soil and on recently constructed near-shore islands. Most of the serious damage to larger commercial and industrial buildings and infrastructure occurred in areas of soft soils and reclaimed land. The worst industrial damage occurred at or near the waterfront due to ground failures-liquefaction, lateral spreading, and settlement. .
             The Port of Kobe was an extreme example of the problems associated with poor soils in areas prone to earthquakes. The port is built almost entirely on fill. The engineering profession has tried hard to develop methods for strengthening filled areas to resist failures during earthquakes, but most of these methods have been put into practice without the benefit of being adequately tested in strong earthquakes.