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我国是一个多地震的国家,每当大地震一发生,地震工作者立即根据各台站的地震仪器记录,利用走时表,迅速定出表中位置,以便及时准确地奔赴灾区,进行抗震救灾。因此,走时表准确与否,是极为重要的。长期以来我国一直使用捷夫瑞斯-布伦(Jeffreys-Bullen)在1940年发表的走时表(简称J-B表),虽然在使用过程中对这个表作了一些改进,但在我国实际应用中仍然存在不少误差,因为它是利用日本、欧洲、北美、南美及太平洋中的一些地震资料计算出的世界平均表,远不能满足我国日益发展的地震工作需要。
China is a country with many earthquakes. Whenever a major earthquake happens, the earthquake worker immediately sets up the position in the table according to the records of the seismic instruments at each station and makes use of the travel timetable to promptly and accurately go to the disaster-hit areas for earthquake relief. Therefore, it is extremely important to take the timetable accurately. For a long time our country has been using Jeffreys-Bullen’s time-table (JB) published in 1940. Although some improvements have been made to this table during its use, it still exists in our country’s practical application A lot of errors because it is a world average table calculated by using some seismic data in Japan, Europe, North America, South America and the Pacific far from being able to meet the needs of the increasingly developed seismic work in our country.