Coda power and modulation characteristics of a complex P signal from underground nuclear explosions

Subhash, Shiv Mohan G.; Choudhury, Mansur A.

doi:10.1016/0040-1951(79)90350-0

Cited by 3 publications

(2 citation statements)

References 2 publications

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“…The ability of P codas to discriminate seismic waves of earthquakes and explosions was also studied by Evernden (1977) and Evernden and Kohler (1979). Other studies of the stability of the P coda and the variability of direct P can be found in Subash and Choudhury (1979), and Aki (198la). Baumgardt (1985) offers a P and Lg analysis of long term codas recorded at GRAEFENBERG and NORSAR arrays, from possible underground nuclear tests in western Russia.…”

Section: Part Iv: P Codas; Description and Applicationsmentioning

confidence: 99%

Scattering and attenuation of high-frequency seismic waves; development of the theory of coda waves

Herráiz¹,

Espinosa²

1986

Open-File Report

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Coda waves are one of the most striking features recorded on seismograms, and their study has bloomed over the last 10 years. Scattering and attenuation of high-frequency seismic waves constitute key subjects in both theoretical and applied research in present-day seismology. However, the narrow relations among coda waves, scattering, and attenuation are not taken into account often enough, nor is an overall comprehension of these subjects always offered. Coda waves of local earthquakes can be considered as backscattered 5 to 5 waves, and the quality factor which accounts for their decay, Q c , expresses both absorption and scattering-attenuation effects. How scattering constructs coda waves and contributes to their attenuation is not completely understood; work now in progress will improve the understanding of scattering theory. This review describes coda waves in detail and discusses their relation to attenuation in the context of research on seismic-scattering problems. Care has been taken to explain the statistical models used to deal with the heterogeneities responsible for scattering. The important role played by observational data is also stressed. where r\ and f2 define the points at which a fluctuation is measured and the average is made over an ensemble of the random media. Initially, N(f') adopted Gaussian or exponential forms. In the latest studies Von Karman functions are preferred. correlation distance, a It expresses the separation for which fluctuations become uncorrelated in the statistical study. It is also called "inhomogeneity scale length". uniform random field, N(r) depends only on the difference r\-TI. isotropic random field, N(f'} depends only on the modulus of r\-f^. normal random field, N(r) has the form of a Gaussian curve N(f) = JV(f0)e-r2/°'a (2) wave parameter, D Ratio of the size of the first Fresnel zone to the scale length of inhomogeneities. It can be given by the expression: D=t (3) K0t* where K is the wave number. Uses the Born approximation r=R»A .

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Section: Part Iv: P Codas; Description and Applicationsmentioning

confidence: 99%

Scattering and attenuation of high-frequency seismic waves; development of the theory of coda waves

Herráiz¹,

Espinosa²

1986

Open-File Report

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“…Hurley used broad-band body waves and long-period surface waves to demonstrate that the anomalous signals were generated by a pair of explosions fired simultaneously but some 30km apart. Subhash and Choudhury (1979) and Burger, Burdick and Lay (1986) have also shown, using teleseismic P-waves, that the source was a multiple explosion.…”

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confidence: 90%

Seismic P-waves from Novaya Zemlya explosions: seeing double!

Stewart¹,

Marshall²

1988

Geophysical Journal International

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SUMMARY The P‐wave seismograms generated by an underground explosion on 11 October, 1980 at the northern Novaya Zemlya test site are quite different from the seismograms normally recorded from explosions there. However, the PcP seismograms are similar to the PcPs normally observed. A simple deconvolution of the seismograms yields pulse shapes that are interpreted as being generated by two simultaneous explosions, some 7 km apart. The spatial separation causes the appearance of the P‐wave seismograms to change with azimuth, but such variation is not observed in PcP because the steeply‐descending wavefronts from each explosion are superpositioned. The observed P‐wave seismograms from the double explosions are successfully modelled using the observed PcP as the source function.

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