SUMMARY

Surface waves are usually dispersive with long wave trains and steady decay of amplitude with distance. However, if the group velocity is nearly constant for a span of periods a strong pulse is produced that retains its amplitude for large distances. This situation arises for the fundamental mode of Love waves in the period band 40–500 s for crust and mantle structures with a positive gradient of S wave speed in the uppermost mantle. Such a distinct Love-wave pulse with limited dispersion observed at teleseismic distance is termed the G wave in honour of Gutenberg. The long-period G-wave pulse caused by large earthquakes carries a large amount of energy to substantial distances, with significant effects across the globe, for example event triggering. A similar G-type Love-wave pulse with a much shorter-period of 10–20 s is generated for crustal structures without thick sediment. Such pulses produce anomalously large ground displacement at near-regional distances with, for example an overestimate of surface wave magnitude. We investigate the generation and propagation mechanism of the G-type Love-wave pulses in the crust and upper-mantle with the analysis of observed strong motion records from the M_w 6.2 2016 Central Tottori earthquake and the M_w 9.0 2011 Off Tohoku earthquake in Japan, in conjunction with 3-D finite-difference simulation of seismic wave propagation and analysis of dispersion curves.

中文翻译：

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在大陆和海洋环境中，不同的爱波脉冲从区域到远震距离的传播

概要

表面波通常随着长波列而散布，并且振幅随距离而稳定衰减。但是，如果组速度在一段时间跨度内几乎保持恒定，则会产生一个强脉冲，该脉冲在较长距离内保持其振幅。这种情况是由于地壳和地幔结构在40-500 s周期带内的Love波的基本模式出现的，最上层地幔中的S波速呈正梯度。在远震距离观察到的这种具有有限色散的独特爱波脉冲被称为G波，以纪念古腾堡。由大地震引起的长周期G波脉冲将大量能量携带到相当远的距离，从而在全球范围内产生重大影响，例如事件触发。对于没有厚沉积物的地壳结构，会产生类似的G型洛夫波脉冲，周期短得多，为10–20 s。这样的脉冲会在近距离区域产生异常大的地面位移，例如表面波幅度的高估。我们通过对M观测到的强运动记录的分析，研究了地壳和上地幔中G型洛夫波脉冲的产生和传播机理。_瓦特6.2 2016中部鸟取地震和M个_瓦特在日本9.0 2011关东北地震，与地震波传播和散曲线分析的3-d的有限差分模拟相结合。