• journal_title：Bulletin of the Seismological Society of America
• Contributor：Igor B. Morozov ; Chaoying Zhang ; Joel N. Duenow ; Elena A. Morozova ; Scott B. Smithson
• Publisher：Seismological Society of America
• Date：2008-
• Format：text/html
• Language：en
• Identifier：10.1785/0120080037
• journal_abbrev：Bulletin of the Seismological Society of America
• issn：0037-1106
• volume：98
• issue：6
• firstpage：2615
• section：Articles

Frequency-dependent coda attenuation values are often reported; however, such measurements usually depend on the types of the Q(f) models employed. We use numerical modeling of peaceful nuclear explosion (PNE) coda at far-regional to teleseismic distances to compare two such models, namely, the conventional frequency-dependent quality factor (Q_coda(f)=Q₀f^η) and frequency-independent coda attenuation (Q_c) with geometrical attenuation (γ). The results favor strongly the (γ,Q_c) model and illustrate the mechanisms leading to apparent Q_coda(f) dependencies. Tests for variations of the crustal velocity structures show that the values of γ are stable and related to lithospheric structural types, and the inverted Q_c-values can be systematically mapped into the true S-wave attenuation factors within the crust. Modeling also shows that γ could increase in areas where relatively thin attenuating layers are present within the crust; such areas could likely be related to younger and active tectonics. By contrast, when interpreted by using the traditional (Q₀,η) approach, the synthetic coda shows a strong and spurious frequency dependence with η≈0.5, which is also similar to the observations.

Observed Lg coda from two PNEs located in different areas in Russia show similar values of γ≈0.75×10^-2 sec^-1, which are also remarkably close to the independent numerical predictions. At the same time, coda Q_c-values vary strongly, from 850 in the East-European platform to 2500 within the Siberian Craton. This suggests that parameters γ and Q_c could provide stable and transportable discriminants for differentiating between the lithospheric tectonic types and ages and also for seismic coda regionalization in nuclear test monitoring research.