With such a long-lasting earthquake, we saw 7 structures that might have been okay after 30 seconds just continued to sink and tilt as the shaking continued for several more minutes, he said. And it was clear that younger sediments, and especially areas built on 8 filled ground, are much more vulnerable.
The data provided by analyzing the Japanese earthquake, researchers said, should make it possible to improve the understanding of this soil 9 and better prepare for it in the future. Ashford said it was critical for the team to collect the information quickly, 10 damage was removed in the recovery efforts.
Theres no doubt that well learn things from what happened in Japan 10 that11 will help us to reduce risks in other similar 11 , Ashford said. Future construction in some places may make more use of techniques known to reduce liquefaction, such as better compaction to make soils dense, or use of reinforcing stone columns.
Ashford pointed out that northern California have younger soils vulnerable to liquefaction ---on the coast, near river deposits or in areas with filled ground. The young sediments, in geologic terms, may be those 12 within the past 10,000 years or more. In Oregon, for instance, that describes much of downtown Portland, the Portland International Airport and other cities.
Anything 13 a river and old flood plains is a suspect , and the Oregon Department of Transportation has already concluded that 1,100 bridges in the state are at risk from an earthquake. Fewer than 15 percent of them have been reinforced to 14 collapse. Japan has suffered tremendous losses in the March 11 earthquake, but Japanese construction 15 helped prevent many buildings from collapse ---even as they tilted and sank into the ground.
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