单个的宽频带地震图可观测到远距离大地震的近场震相。甚至在距离为20°～30°时,这样的震相仍有十分之几毫米的振幅。尽管以前的研究曾在垂向分量中作过识别,但这种近场震相在横向分量中可更容易地观测到。虽然观测效应与采用点矩张量源的全波计算吻合较好,但仍不能满足在地震资料分析中通常所做的某些假设。因此,建议在对可能含有这种效应的甚宽频带地震图进行分析时多加小心。作为一个恰当的例子,这里显示了最新观测到的W震相。 A single broadband seismogram can be used to observe the near-field seismic phase of large-scale long-distance earthquakes. Even in the distance of 20 ° ~ 30 °, such a phase is still a few tenths of a millimeter amplitude. Although previous studies have identified in the vertical component, this near-field phase can be more easily observed in the horizontal component. Although the observed effect is in good agreement with the full-wave calculation using moment tensor sources, some of the assumptions usually made in seismic data analysis can not be satisfied. Therefore, it is advisable to exercise caution in the analysis of very broad-band seismograms that may contain such effects. As a good example, the latest observed W phase is shown here.