Propagation of distinct Love-wave pulses from regional to teleseismic distances in continental and oceanic environments

Autor: Brian Kennett, Takashi Furumura
Rok vydání: 2020
Předmět:
Zdroj: Geophysical Journal International. 221:665-682
ISSN: 1365-246X
0956-540X
DOI: 10.1093/gji/ggaa028
Popis: SUMMARYSurface 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 Mw 6.2 2016 Central Tottori earthquake and the Mw 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.
Databáze: OpenAIRE
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