TRAVELTIMES FOR GLOBAL EARTHQUAKE LOCATION AND PHASE IDENTIFICATION
TRAVELTIMES FOR GLOBAL EARTHQUAKE LOCATION AND PHASE IDENTIFICATION
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DOI：
10.1111/j.1365-246x.1991.tb06724.x
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发表时间：
1991-05-01
影响因子：
2.8
通讯作者：
ENGDAHL, ER
中科院分区：
文献类型：
--
作者：
KENNETT, BLN;ENGDAHL, ER
在过去三年中，国际地震学和地球内部物理学协会（IASPEI）地震算法小组委员会做出了重大的国际努力，以生成新的地震震相全球走时表，以更新Jeffreys和Bullen（1940年）的表。 新表格专为方便计算使用而设计，在深度和范围上都具有高精度插值。 新的iasp 91走时表是从径向分层速度模型导出的，该模型的构造使主要地震阶段的时间与1964-1987年期间国际地震中心目录中报告的事件时间一致。 iasp 91模型中的P波走时的基线已被调整，以便仅为世界各地主要核试验场的良好约束事件提供起源时间的小偏差。新表比1968年的P表（Herrin 1968）慢约0.7秒，平均比Jeffreys & Bullen（1940）表快约1.8-1.9秒。 对于S波，其走时介于JB表的走时和Randall（1971）的结果之间，由于各震相的走时都是由同一速度模型导出的，所以不同震源深度处不同震相的走时是完全一致的。 新iasp 91表采用的计算方案是Buland & Chapman（1983）提出的方案。 延迟时间作为慢度的函数的表被存储为每个走时分支，并且使用专门设计的tau样条插值，该tau样条在某些临界慢度处照顾走时曲线的导数中的平方根奇异性。 有了这种表示，一旦指定了震源深度，就可以直接找到给定震中距离的走时。 计算成本不高于传统的查找表，但在构建任意深度处的源的走时时有增加的精度。 与标准表格相比的另一个优点是，每个阶段都可以使用完全相同的程序。 因此，对于给定的震源深度，可以非常快速地生成在给定震中距离处可以观察到的主要地震震相的走时和相关导数的全面列表。
Over the last three years, a major international effort has been made by the Sub-Commission on Earthquake Algorithms of the International Association of Seismology and the Physics of the Earth's Interior (IASPEI) to generate new global traveltime tables for seismic phases to update the tables of Jeffreys & Bullen (1940). The new tables are specifically designed for convenient computational use, with high-accuracy interpolation in both depth and range. The new iasp91 traveltime tables are derived from a radially stratified velocity model which has been constructed so that the times for the major seismic phases are consistent with the reported times for events in the catalogue of the International Seismological Centre (ISC) for the period 1964-1987. The baseline for the P-wave traveltimes in the iasp91 model has been adjusted to provide only a small bias in origin time for well-constrained events at the main nuclear testing sites around the world.For P-waves at teleseismic distances, the new tables are about 0.7s slower than the 1968 P-tables (Herrin 1968) and on average about 1.8-1.9 s faster than the Jeffreys & Bullen (1940) tables. For S-waves the teleseimic times lie between those of the JB tables and the results of Randall (1971).Because the times for all phases are derived from the same velocity model, there is complete consistency between the traveltimes for different phases at different focal depths. The calculation scheme adopted for the new iasp91 tables is that proposed by Buland & Chapman (1983). Tables of delay time as a function of slowness are stored for each traveltime branch, and interpolated using a specially designed tau spline which takes care of square-root singularities in the derivative of the traveltime curve at certain critical slownesses. With this representation, once the source depth is specified, it is straightforward to find the traveltime explicitly for a given epicentral distance. The computational cost is no higher than a conventional look-up table, but there is increased accuracy in constructing the traveltimes for a source at arbitrary depth. A further advantage over standard tables is that exactly the same procedure can be used for each phase. For a given source depth, it is therefore possible to generate very rapidly a comprehensive list of traveltimes and associated derivatives for the main seismic phases which could be observed at a given epicentral distance.