当前位置: X-MOL 学术Prog. Earth Planet. Sci. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Significant P wave conversions from upgoing S waves generated by very deep earthquakes around Japan
Progress in Earth and Planetary Science ( IF 3.5 ) Pub Date : 2019-07-09 , DOI: 10.1186/s40645-019-0292-z
B. L. N. Kennett , T. Furumura

An important component of the seismic wavefield at moderate epicentral distances from deep earthquakes comes from seismic waves that are radiated upwards from the source. For very deep events, there is a range of distances at which upgoing S can convert into P waves that travel in the crust or in the upper mantle as the sPn phase. For a 600-km-deep event, sPn becomes a precursor to S from about 8°, and can have significant amplitude if the source radiation pattern is favourable. These conversions to crustal P have a very similar travel time property to S, and interfere strongly with S to produce complex wavetrains on both vertical and radial components. Where the locus of conversion falls on thicker continental crust, S waves can be coupled into partially trapped P waves in the crust that produce a long-period shear-coupled PL (s-PL) wave. Such longer period phases generated by large, very deep earthquakes can make a major contribution to sustaining large ground motion for considerable distances from the source. Observations of three very deep (> 575 km) events around Japan demonstrate the range of propagation effects associated with S to P wave (sP) conversion that plays an important role in shaping the later part of the recorded seismograms. The influence of sP conversion on the observed seismograms and the development of the s-PL wave depend on the variation of crustal thickness along the path and epicentral distance, and particularly on the locus of the conversion zone and the properties of the crust at that location.


中文翻译:

由日本周围极深地震产生的上行S波产生的显着P波转换

距深地震震中距离适中的地震波场的重要组成部分是从震源向上辐射的地震波。对于非常深的事件,在一定距离范围内,上行的S可以转换为P波,并以sPn相的形式在地壳或上地幔中传播。对于深达600公里的事件,sPn从约8°开始成为S的前兆,并且如果源辐射图有利,则sPn的幅度可能会很大。这些到地壳P的转换与S具有非常相似的传播时间特性,并且强烈干扰S在垂直和径向分量上产生复杂的波列。在转换的轨迹落在较厚的大陆壳上的情况下,S波可以耦合为地壳中部分捕获的P波,从而产生长周期的剪切耦合PL(s-PL)波。由巨大的非常深的地震产生的这种较长的阶段,可以为在距震源相当远的距离上维持较大的地面运动做出重大贡献。在日本附近发生的三起非常深的事件(> 575 km)的观测结果表明,与S到P波(sP)转换有关的传播效应范围在塑造记录的地震图的后期部分中起着重要作用。sP转换对观察到的地震图和s-PL波发展的影响取决于地壳厚度沿路径和震中距离的变化,尤其取决于转换区的轨迹和该位置的地壳特性。非常深的地震可以为在距震源相当远的距离上维持较大的地面运动做出重大贡献。对日本三处非常深(> 575 km)事件的观察表明,与S波到P波(sP)转换相关的传播效应范围在塑造记录的地震图的后期部分中起着重要作用。sP转换对观察到的地震图和s-PL波发展的影响取决于地壳厚度沿路径和震中距离的变化,尤其取决于转换区的轨迹和该位置的地壳特性。非常深的地震可以为在距震源相当远的距离上维持较大的地面运动做出重大贡献。在日本附近发生的三起非常深的事件(> 575 km)的观测结果表明,与S到P波(sP)转换有关的传播效应范围在塑造记录的地震图的后期部分中起着重要作用。sP转换对观察到的地震图和s-PL波发展的影响取决于地壳厚度沿路径和震中距离的变化,尤其取决于转换区的轨迹和该位置的地壳特性。日本周围的575公里)事件表明,与S到P波(sP)转换相关的传播效应范围在塑造记录的地震图的后期部分中起着重要作用。sP转换对观察到的地震图和s-PL波发展的影响取决于地壳厚度沿路径和震中距离的变化,尤其取决于转换区的轨迹和该位置的地壳特性。日本周围的575公里)事件表明,与S到P波(sP)转换相关的传播效应范围在塑造记录的地震图的后期部分中起着重要作用。sP转换对观察到的地震图和s-PL波发展的影响取决于地壳厚度沿路径和震中距离的变化,尤其取决于转换区的轨迹和该位置的地壳特性。
更新日期:2019-07-09
down
wechat
bug