Travel times of P and S from the global digital seismic networks:: Implications for the relative variation of P and S velocity in the mantle
Travel times of P and S from the global digital seismic networks:: Implications for the relative variation of P and S velocity in the mantle
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DOI：
10.1029/2000jb900378
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发表时间：
2001-07-10
影响因子：
3.9
通讯作者：
Masters, G
中科院分区：
文献类型：
--
作者：
Bolton, H;Masters, G
我们提出了新的数据集的P和S的到达时间已被精心挑选的长期垂直和横向分量记录的各种全球地震网络。利用1976年至1994年发生的事件，得到了类似于38，000个全球分布均匀的P的测量值和类似于41，000个S的测量值。这些数据对于研究下地幔S和P速度的相对变化特别有用。我们描述了测量技术和数据集的总体特征。我们的数据集的大小允许我们利用数据的内部一致性，使用摘要射线分析来识别离群值。由于每个到达的极性也是已知的，因此我们可以构造断层面解和/或与由哈佛质心矩张量解预测的极性进行比较，以进一步诊断相位错误识别。这种分析的结果是大约5%的数据被识别为离群值。方差分析表明，S剩余走时的三维结构的影响占主导地位，但P数据具有可比的贡献，从噪声和源错位的影响。综合射线分析揭示了下地幔结构的基本特征，S、P数据集均具有大尺度的模式，且相关性较好。这一分析表明，平均而言，dlnv（s）/dlnv（p）是地幔深度的递增函数，从下地幔顶部的1.7到地幔底部附近的4。后一个极端值的R似乎主要是由于数据的样本在最低的地幔下的中太平洋，大的正S残差与非常小的P残差的一个区域。这种异常现象不可能是热成因的。
We present new data sets of P and S arrival times which have been handpicked from long-period vertical and transverse component recordings of the various global seismic networks. Using events which occurred from 1976 to 1994 results in similar to 38,000 globally well-distributed measurements of teleseismic P and similar to 41,000 measurements of S. These data are particularly useful for looking at the relative variation of S and P velocities in the lower mantle. We describe both the measurement techniques and the gross characteristics of the data sets. The size of our data sets allows us to exploit the internal consistency of the data to identify outliers using a summary ray analysis. Since the polarity of each arrival is also known, we can construct fault plane solutions and/or compare with polarities predicted by the Harvard centroid moment tensor solutions to further diagnose phase misidentification. This analysis results in similar to5% of the data being identified as outliers. An analysis of variance indicates that the S residual travel times are dominated by the effects of three-dimensional structure but the P data have comparable contributions from noise and source mislocation effects. The summary ray analysis reveals the basic character of lower mantle structure, and there are large-scale patterns in both the S and P data sets that correlate quite well with each other. This analysis suggests that on average, d ln v(s)/d ln v(p) is an increasing function of depth in the mantle going from a value of similar to1.7 at the top of the lower mantle to an apparent value of 4 near the base of the mantle. This latter extreme value of R seems to result mainly from data which sample one region in the lowermost mantle under the central Pacific, where large positive S residuals are associated with very small P residuals. Such an anomaly cannot be thermal in origin.