A Time Domain Study of Tectonic Strain Release Effects on Seismic Waves from Underground Nuclear Explosions PDF Download

Author: K. K. Nakanishi
Publisher:
ISBN:
Category : Blast effect
Languages : en
Pages : 36

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Author:
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Category :
Languages : en
Pages :

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Seismic surface-wave generation by underground nuclear explosions releasing tectonic strain is studied through a series of synthetic radiation-pattern calculations based on the earthquake-trigger model. From amplitude and phase radiation patterns for 20-s Rayleigh waves, inferences are made about effects on surface-wave magnitude, M/sub s/, and waveform character. The focus of this study is a comparison between two mechanisms of tectonic strain release: strike-slip motion on vertical faults and thrust motion on 45° dipping faults. The results of our calculations show that Rayleigh-wave amplitudes of the dip-slip model at F values between 0.75 and 1.5 are significantly lower than amplitudes of the strike-slip model or of the explosion source alone. This effect translates into M/sub s/ values about 0.5 units lower than M/sub s/ of the explosion alone. Waveform polarity reversals occur in two of four azimuthal quadrants for the strike-slip model and in all azimuths of the dip-slip-thrust model for F values above about 3. A cursory examination of waveforms from presumed explosions in eastern Kazakhstan suggests that releases of tectonic strain are accompanying the detonation of many of these explosions. Qualitatively, the observations seem to favor the dip-slip-thrust model, which, in the case of a few explosions, must have F values above 3.

Author:
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ISBN:
Category : Power resources
Languages : en
Pages : 1226

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Author: Rodolfo Console
Publisher:
ISBN:
Category : Nature
Languages : en
Pages : 476

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This volume presents different studies carried out on induced seismicity, both from experimental and theoretical viewpoints. Several examples of seismic activity induced by underground nuclear explosions, impoundment of artificial reservoirs, and mining activities are given and discussed. Another important subject which is covered is earthquakes induced by other large earthquakes. Further, tectonic stress release in the immediate vicinity of an underground nuclear explosion is treated. The release produces aftershocks of small magnitude, usually for several weeks, occurring a few kilometers within the shot point. This phenomenon is of importance in the context of monitoring a Comprehensive Test Ban Treaty.

Author: M. Nafi Toksoz
Publisher:
ISBN:
Category :
Languages : en
Pages : 241

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Static and dynamic methods are developed to study the elastic field produced by earthquake faulting. An earthquake is considered as the slip on a planar fault due to frictional instability. The dynamics of a circular fault model is considered as a circular rupture front that expands subsonically from a nucleation point until it suddenly stops at its final radius. It was found that both the final slip on the fault and the rise time are zero on the edge of the fault and reach their maxima at the center of the fault. This slip-time history is quite different from that of the usual Haskell model where slip and rise time are assumed constant over the fault. The far field radiation due to this fault model was studied. A new method to compute the static near field of a shallow earthquake was developed.

Author: M. Nafi Toksoez
Publisher:
ISBN:
Category :
Languages : en
Pages : 42

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Theoretical and observational research has been carried out in order to study tectonic strain. Theoretical calculations for a composite source model consisting of explosive and double couple components were compared to observed surface wave spectral ratios from underground nuclear explosions. A theoretical calculation is presented to explain the observed double couple component associated with tectonic stress release. Results from numerical calculations of induced flow behind island arcs and the associated tectonic stresses are presented. (Author).

Author:
Publisher:
ISBN:
Category : Shock (Mechanics)
Languages : en
Pages : 664

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Author: Brian W. Barker
Publisher:
ISBN:
Category :
Languages : en
Pages : 65

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Large samples of teleseismic P wave amplitude and waveform data recorded from Shagan River underground explosions have been collected and systematically analyzed in an attempt to identify any effects which may correlate with the amount of tectonic release accompanying these explosions. Results of these analyses indicate that these teleseismic P wave data do not provide any unambiguous evidence of effects of tectonic release in the short-period range of interest in m sub b determination. However, the results of a preliminary theoretical analysis indicate that such negative evidence is not definitive in that there are plausible models of tectonic release for which no detectable variations in the observed teleseismic P waveforms are theoretically expected to result from the superposition of these two sources. At the same time, such models of tectonic release predict significant positive bias in the network-averaged m sub b values for explosions accompanied by the mode of tectonic release traditionally associated with the Shagan River test site. Thus, the currently available seismic data do not exclude the possibility that tectonic release may be introducing a positive bias of as much as several tenths of a magnitude unit into the network-averaged m sub b values computed for some Shagan River explositons. Keywords: Explosion seismology; Threshold Test Ban Treaty; Network; USSR; Global Digital Seismic; Seismic body waves; Nuclear explosion detection; Radiation patterns.

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 159

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The seismic motions from nonlinear two dimensional (2D) axisymmetric finite difference calculations of underground explosions are propagated to regional and teleseismic distances. Synthetic seismograms are computed and examined to study the effects of depth of burial, medium structure, and prestress on seismic waveforms. The elastodynamic representation theorem is used to couple the results of finite difference source calculations to regional Green's functions computed using a wavenumber integration algorithm. The 2D finite difference source calculations include the nonlinear effects of gravity, spall, bulking, and cracking as well as the finite extent and divergence from spherical symmetry. The results are broadband full wave regional synthetics for explosion sources with cylindrical symmetry. These theoretical seismograms are studied with regard to proposed regional discriminants between explosions and earthquakes. Explosions, Tectonic release, Depth, Burial, Finite differences, Seismic waveforms.

Author: Zhiqiang Yin
Publisher: Frontiers Media SA
ISBN: 2832505643
Category : Science
Languages : en
Pages : 281

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