PROPAGATION AND ATTENUATION CHARACTERISTICS OF THE CRUSTAL PHASE LG

被引：51

作者：

CAMPILLO, M

机构：

[1] Observatoire de Grenoble, UA CNRS 733, IRIGM, Grenoble, 38402

来源：

PURE AND APPLIED GEOPHYSICS | 1990年 / 132卷 / 1-2期

关键词：

attenuation; coda; crustal structure; Regional seismograms; surface waves;

D O I：

10.1007/BF00874355

中图分类号：

P3 [地球物理学]; P59 [地球化学];

学科分类号：

0708 ; 070902 ;

摘要：

The Lg wave consists of the superposition of S waves supercritically reflected, and thus trapped, in the crust. This mode of propagation explains the strong amplitude of this phase and the large distance range in which it is observed. The numerical simulation leads to successful comparison between observed seismograms in stable continental areas and synthetics computed for simple standard crustal models. In regions with strong lateral variations, the influence of large-scale heterogeneities on the Lg amplitude is not yet clearly established in terms of the geometrical characteristics of the crustal structure. The analysis of the decay of amplitude of Lg with epicentral distance allows the evaluation of the quality factor of S waves in the crust. The results obtained show the same trends as coda Q: a clear correlation with the tectonic activity of the region considered, both for the value of Q at 1 Hz and for its frequency dependence, suggesting that scattering plays a prominent part among the processes that cause the attenuation. The coda of Lg is made up of scattered S waves. The study of the spatial attenuation of the coda indicated that a large part of the arrivals that compose the coda propagate as Lg. The relative amplitude of the coda is larger at sites located on sediments because, in these conditions, a part of Lg energy can be converted locally into lower order surface modes. © 1990 Birkhäuser Verlag.

引用

页码：1 / 19

页数：19

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