| Report on Phase Blockage Phenomenology Session, SSA 91st Annual Meeting, 2 April 1996, St. Louis, Missouri |
05 JUN 96 |
27 pages |
| Authors:
Delaine T. Reiter; Rong-Song Jih; PHILLIPS LAB HANSCOM AFB MA
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 | This report details the results of a special session on regional phase blockage which was held during the Seismological Society of America's 91st Annual Meeting in St. Louis, Missouri on April 2, 1996. The session consisted of seven orally presented papers by members of the seismic monitoring research community and a follow-up meeting that was intended to be a discussion session about the scientific problem of phase blockage. The report ... |
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| A Simple, Causal Method to Incorporate Anelastic Attenuation into Finite-Difference Calculations |
21 DEC 95 |
58 pages |
| Authors:
Rong-Song Jih; PHILLIPS LAB HANSCOM AFB MA
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| Current nuclear treaty monitoring interest has shifted to the verification of a comprehensive test ban treaty (CTBT), including the detection of the first test of potential proliferators. Predictive modeling capabilities are crucial, not just desirable, in the context of CTBT and proliferation monitoring. Synthetic seismograms generated with the linear-finite-difference (LFD) code are particularly useful for regions where earthquake or explosion data are not available. However, to date many LFD modeling ... |
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| Waveguide Effects of Large-Scale Structural Variation, Anelastic Attenuation, and Random Heterogeneity on SV Lg Propagation. A Finite-Difference Modeling Study |
21 DEC 95 |
117 pages |
| Authors:
Rong-Song Jih; PHILLIPS LAB HANSCOM AFB MA
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| Lg is often the most prominent phase on regional seismograms and hence it has been extensively used in various seismic operations: (a) detection and location, (b) source size (earthquake magnitude and explosive yield) estimation, and (c) source type identification (that is, discrimination). However, there have also been many outstanding fundamental questions regarding the excitation and propagation of the Lg phase. This report documents a comprehensive modeling study aimed at quantification ... |
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| Maximum-Likelihood Network Magnitude Estimates of Low-Yield Underground Nuclear Explosions |
31 MAR 94 |
105 pages |
| Authors:
Rong-Song Jih; Richard R. Baumstark; TELEDYNE GEOTECH ALEXANDRIA VA ALEXANDRIA LABS
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| This final report covers the analysis performed under Task 3 of this contract, using the raw station magnitudes collected under Task One. 35,211 station Mb values from 6 major nuclear test sites have been fed into the GLM (general Linear Model) inversion to determine jointly the event sizes, the station corrections, and the specific path correction for each source-station pair. The simultaneously-inferred path and station corrections are related to known ... |
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| Statistical Characterization of Rugged Propagation Paths with Application to Rg Scattering Study |
05 NOV 93 |
186 pages |
| Authors:
Rong-Song Jih; TELEDYNE GEOTECH ALEXANDRIA VA ALEXANDRIA LABS
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| Motivated by many observations of correlation between the free- surface topography and the coda generation at teleseismic and regional distances, seven simple statistics have been tested whether they can fully characterize the roughness of an arbitrary rugged free-surface topography. Based on 2-dimensional finite-difference simulations, the normalized arc length and Durbin-Watson number are identified as the best and the poorest, respectively, roughness measures, in terms of correlating with the propagation behavior ... |
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| Statistical Study of Soviet Nuclear Explosions: Data, Results, and Software Tools |
05 NOV 93 |
87 pages |
| Authors:
Rong-Song Jih; Robert A. Wagner; Robert H. Shumway; TELEDYNE GEOTECH ALEXANDRIA VA ALEXANDRIA LABS
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| This final report summarizes our efforts in analyzing Soviet underground nuclear tests, with emphases on our updated results and the statistical software developed. 28,875 carefully measured station magnitudes were fed into a maximum-likelihood inversion scheme which simultaneously determines the event size and the station correction, as well as the specific path correction for each source-station pair. The simultaneously-inferred path and station corrections are related to known geological/geophysical features. Applying these ... |
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| User's Manual of FD2: A Software Package for Modeling Seismological Problems with 2-Dimensional Linear Finite-Difference Method |
15 JUL 93 |
73 pages |
| Authors:
Rong-Song Jih; TELEDYNE GEOTECH ALEXANDRIA VA ALEXANDRIA LABS
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| Fd2 is a software package developed at Teledyne Geotech Alexandria Laboratories (TGAL) during the past several years for generating synthetic seismograms and displaying the wavefields. This package consists of primarily a 2-dimensional 2nd-order explicit linear finite-difference (LFD) code. LFD method has the advantage that the solution contains all conversions and all orders of multiple scattering. It permits examinations of fairly general models with arbitrary complex variations in material properties and ... |
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| Path-Corrected Body-wave Magnitudes and Yield Estimates of Novaya Zemlya Explosions |
31 AUG 91 |
72 pages |
| Authors:
Rong-Song Jih; Robert A. Wagner; TELEDYNE GEOTECH ALEXANDRIA VA ALEXANDRIA LABS
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| Along with an extensive data set of worldwide explosions recorded at WWSSN, teleseismic short-period body-wave amplitudes from 28 Novaya Zemlya explosions are measured and analyzed to isolate the propagation characteristics and to derive a better measure of the source size. The separation of path effects from station effects provides direct clues as to how an old fold-belt structure (like Novaya Zemlya) could modulate the short-period P-wave amplitude and travel-time patterns. ... |
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| Recent Methodological Developments in Magnitude Determination and Yield Estimation with Applications to Semipalatinsk Explosions |
16 JUL 91 |
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| Authors:
Rong-Song Jih; Robert A. Wagner; TELEDYNE GEOTECH ALEXANDRIA VA ALEXANDRIA LABS
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 | An improved magnitude determination procedure is presented to account for the empirical near-source focusing/defocusing effects. This scheme provides more stable m sub b measurements with a reduction in the fluctuational variation by a factor of up to 3. The events which do not show significant improvement could have been detonated in environments with different focusing patterns. The scatter in the network-averaged m sub b based on the new scheme versus ... |
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| Finite-Difference Modeling of Rayleigh Wave Scattering and P-SV(Lg) Coupling Problems |
MAR 88 |
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| Authors:
Rong-Song Jih; Keith L. McLaughlin; TELEDYNE GEOTECH ALEXANDRIA VA ALEXANDRIA LABS
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| The work has focused on the effects on near-source heterogeneity upon seismic wave scattering and phase conversions. The basic tool was a developing 2-dimensional explicit linear finite-difference code. By use of various initial conditions and/or the principle of reciprocity. One can generate the teleseismic response of the Earth model to a general seismic source. The propagation of Pn/ Sn/Rg phases with some Arctic paths are also modeled without using the ... |
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| Investigation of Explosion Generated SV Lg Waves in 2-D Heterogeneous Crustal Models by Finite-Difference Method |
FEB 88 |
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| Authors:
Rong-Song Jih; Keith L. McLaughlin; TELEDYNE GEOTECH ALEXANDRIA VA ALEXANDRIA LABS
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| A linear finite-difference (FD) method was used to compare the excitation of far-field P- and SV-waves generated by shallow dilatational sources in a suite of heterogeneous 2-D crustal models. The crustal models tested included simple layered structures, media with random velocity perturbations having Gaussian or self-similar autocorrelation functions, media with rough or gentle topography generated by Markov chains, and laminated media with sinusoidal folds. The numerical experiments were conducted by ... |
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| Finite-Difference Simulations of Rayleigh-Wave Scattering by Shallow Heterogeneity |
NOV 87 |
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| Authors:
Keith L. McLaughlin; Rong-Song Jih; TELEDYNE GEOTECH ALEXANDRIA VA ALEXANDRIA LABS
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| Rayleigh waves normally incident upon 2-D shallow heterogeneity are simulated by the linear finite-difference method to study attenuation, transmission, and reflection of Rayleigh waves and to measure the Rayleigh-to-P and -SV body wave conversion. Transmission, reflection, and scattering depend on the depth, average scale size of the heterogeneity and the amplitude of the spatial fluctuation of velocity. As expected, larger spatial variation in velocity attenuates Rayleigh waves more than smooth ... |
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| Finite-Difference Modeling of Seismological Problems in Magnitude Estimation Using Body Waves, Surface Waves and Seismic Source Imaging |
MAR 87 |
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| Authors:
Keith L. McLaughlin; Zoltan A. Der; Rong-Song Jih; Alison C. Lees; Lisa M. Anderson; TELEDYNE GEOTECH ALEXANDRIA VA ALEXANDRIA LABS
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| Contents: Boundary Conditions for Arbitrary Polygonal Topography in a 2-D Elastic Finite-Difference Scheme for Seismogram Generation; Teleseismic Spectral and Temporal M sub 0 and Psi sub infinity Estimates for four French Explosions in Southern Sahara; Scattering from Near-Source Topography: Teleseismic Observations and Numerical 2-D Explosive Line Source Simulations; Effects of Local Geologic Structure on Yucca Flats, NTS, Explosion Waveforms: 2- Dimensional Linear Finite Difference Simulations; Finite-Difference Simulations of Rayleigh Wave ... |
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| The Effects of Near-Source Topography on Explosion Waveforms: Teleseismic Observations and Linear Finite Difference Calculations |
JUL 86 |
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| Authors:
Keith L. McLaughlin; Rong-Song Jih; Zoltan A. Der; Alison C. Lees; TELEDYNE GEOTECH ALEXANDRIA VA ALEXANDRIA LABS
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| This report consists of three papers: Boundary Conditions for Arbitrary Polygonal Topography in a 2-D Elastic Finite-difference Scheme for Seismogram Generation; Teleseismic Spectral and Temporal Explosion Moment and Reduced Displacement Potential Estimates for Four French Explosions in Southern Sahara; Scattering from Near-Source Topography -- Teleseismic Observations and Numerical 2-D Explosive Line Source Simulations; Keywords: Primary seismic waves, Deconvolution; Two dimensional; Seismic data; Ahaggar Plateau. |
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