Near-source scattering of Rayleigh to P in teleseismic arrivals from Pahute Mesa (NTS) shots

Gupta, Indra N.; McElfresh, T.W.; Wagner, Robert A.

doi:10.1029/gm065p0151

Cited by 13 publications

(9 citation statements)

References 15 publications

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“…The use of near-surface crustal scatterers simplifies our computations, and it is also justified by the increased heterogeneity of the shallow crust and supported by several array observations (e.g., Greenfield, 1971;Dainty, 1985 andBannister et al, 1990;Gupta et al, 1991) and previous coda modeling (Dainty and Schultz, 1995). The choice of the P-wave coda is due to several reasons (Morozov and Smithson, 2000): 1) S-and L g phases are less pronounced in the PNE records; 2) their codas lie on top of the Pwave coda, complicating the observation and requiring their decomposition; and 3) L g phase is significantly more difficult to model accurately.…”

Section: Modeling P-wave Coda Of Pne Arrivalsmentioning

confidence: 99%

“…In regard to the geometrical attenuation parameter  in equation (4), it could be either negative (corresponding, for example, to strong reflected and diving waves returning additional energy to the surface) or positive, as observed in our modeling. Values of  > 0 correspond to the scattered energy decaying with distance faster than surface waves, which should be a common case due to: 1) high attenuation of surface waves in the weathered zone (note the Complex Crust model, Figure 8), and 2) multiple reflections and scattered seismic waves leaking into the mantle as suggested, for example, by Gupta et al (1991). Interestingly, in the "realistic" crust/mantle models considered, (Q S ) is not constant and decreases from ~3-4 at Q S = 100 to about ~1 -1.4 at Q S = 1000 (Figure 8).…”

Section: (Q S ) and Modal Content Of Coda Wavefieldmentioning

confidence: 99%

See 1 more Smart Citation

Frequency Dependence of Coda Q, Part I: Numerical Modeling and Examples from Peaceful Nuclear Explosions

Morozov¹,

Zhang²,

Duenow³

et al. 2008

Bulletin of the Seismological Society of America

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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) codas at far regional to teleseismic distances to compare two of such models, namely the conventional frequency-dependent Q coda (f) = Q 0 f  and frequency-independent coda attenuation (Q c ) with geometrical attenuation (). The results favor strongly the (, 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  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  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 (Q 0 ,) approach, the synthetic coda shows a strong and spurious frequency dependence with   0.5, which is also similar to the observations. Observed Lg codas from two Peaceful Nuclear Explosions located in different areas in Russia show similar values of   0.75·10 -2 s -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  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.

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Section: Modeling P-wave Coda Of Pne Arrivalsmentioning

confidence: 99%

Section: (Q S ) and Modal Content Of Coda Wavefieldmentioning

confidence: 99%

Frequency Dependence of Coda Q, Part I: Numerical Modeling and Examples from Peaceful Nuclear Explosions

Morozov¹,

Zhang²,

Duenow³

et al. 2008

Bulletin of the Seismological Society of America

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“…The relatively slow velocity of R g provides a mechanism for generating significant P energy far after the first arrival with only a single scattering event. Evidence exists for such a mechanism based on nuclear explosion data from Nevada Test Site (Stead & Helmberger, 1988;Gupta et al, 1991). However, for this mechanism to be viable the earthquakes in this area would have to be especially shallow, as R g excitation drops off significantly with increasing source depth.…”

Section: Properties Of Later-arriving Coda Wavesmentioning

confidence: 99%

Model P Wave Multipathing at Regional Distances in Southeast Asia

Koper¹,

Fatehi²

2008

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“…This may also explain the difference between the shapes of the observed ( Figure 7) and the theoretical ( Figure 9) spectral nulls (the observed nulls for source depths of 250-150 m are much broader than the theoretical). It seems, however, that for frequencies below 2 Hz, the homogeneous half-space model is a fairly good approximation to the layered NTS model (Gupta et al, 1991b), so that a rough estimate of depth of the CLVD source for an explosion will be Y/(16 f) where V is its overburden velocity and f is its observed spectral null frequency. These estimates, included in Table 1, suggest that depth of the CLVD source for each explosion is on the average about 0.31, or one-third of its shot depth.…”

Section: Dependence Of Spectral Nulls On Shot Depthmentioning

confidence: 99%

Near-source scattering of Rayleigh to P in teleseismic arrivals from Pahute Mesa (NTS) shots

Cited by 13 publications

References 15 publications

Frequency Dependence of Coda Q, Part I: Numerical Modeling and Examples from Peaceful Nuclear Explosions

Frequency Dependence of Coda Q, Part I: Numerical Modeling and Examples from Peaceful Nuclear Explosions

Model P Wave Multipathing at Regional Distances in Southeast Asia

Study of Low and Lg from Explosions and Its Application to Seismic Monitoring of the CTBT

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