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地面反射的各类转换波,一般容易识别。地壳及上地幔间断面的各类转换波,振幅微小,识别和应用有困难。 我们对牡丹江台1974年以来记录的Δ>20°的一些深震进行了分析,发现初至P波之后15秒有一明显震相,该震相属地下146公里间断面的转换折射波,定名为PiS。在地震图上,转换波PiS的特点是: 1.PiS波迟于原生初至P波,早于pP、sP,PiS-P到时差较稳定,随震中距变化较小。
Reflected on the ground all kinds of converted waves, generally easy to identify. Various types of converted waves in the crust and upper mantle discontinuities have small amplitude and are difficult to identify and apply. We analyzed some deep earthquakes with Δ> 20 ° recorded since Mudanjiangtai since 1974. We found that there was a significant seismic phase 15 seconds after the first P wave. This seismic phase belongs to the converted refracted wave of the 146 km underground section and is named as PiS. On the seismogram, the characteristics of the converted wave PiS are: 1.PiS wave is later than primary P wave, earlier than pP, sP and PiS-P, the time difference is relatively stable and varies little with the epicenter distance.