16 pages : 28 cm

Topics: Rayleigh waves, Atmospheric waves

Research related to the detection, location, and identification of underground nuclear explosion devoted to several major problem areas has been completed. Effects of earth structure and focal mechanism on body-wave magnitude determinations have been investigated, and empirical relations between nuclear yield and Rayleigh wave magnitudes established for selected seismograph stations. Calculations of crustal transmission coefficients for P-waves have been extended to take into account dip and...

Topics: DTIC Archive, Kisslinger, Carl, SAINT LOUIS UNIV MO DEPT OF EARTH AND ATMOSPHERIC SCIENCES,...

Six additional Ocean-Bottom Seismographs, similar in design and functionally interchangeable with existing units, were produced. Results of testing the new units showed that system performance is not measurably affected by the unit modifications and that the replacement Hall-Sears seismometer package is operationally similar to the EV-17 but is more dependable. Shallow bottom sediments in the test area are highly layered, supporting several propagation modes. Shear velocities vary rapidly in...

Topics: DTIC Archive, BeAbout, Edgar G, TEXAS INSTRUMENTS INC DALLAS SCIENCE SERVICE DIV, *SEISMOGRAPHS,...

An investigation of scattering from surface cracks has been conducted. In particular, the change in the reflection coefficient of a Rayleigh wave incident on a surface indentation crack has been measured as the sample is stressed to fracture. The acoustic measurements have been correlated with the stable crack extension that precedes final failure. The crack extension behavior in as-intended and annealed specimens was found to be appreciably different. The cracks in the annealed samples...

Topics: DTIC Archive, Tien,J J W, STANFORD UNIV CA EDWARD L GINZTON LAB OF PHYSICS, *CERAMIC MATERIALS,...

The character of surface wave scattering at local distances depends strongly upon surface topography and local crustal structure. Ultrasonic methods were used to investigate the behavior of seismic waves propagating through scale models of topographic structures suspected of contributing to the scattering of seismic waves. Simple models, consisting of steps and rectangular-and triangular-shaped 'mountains' of varying dimension, were used in an empirical analysis of scattering of surface waves....

Topics: DTIC Archive, Toksoz,M Nafi, MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF EARTH AND PLANETARY...

The probability density function (PDF) for linear glint has been calculated for the situation in which the tracking angles derived from the co- and cross-polarized echoes are combined to produce an averaged tracking angle. A target consisting of two scattering centers, each producing an echo signal with a Rayleigh distribution, was assumed, and two methods of combining the tracking angles were investigated. The PDFs were generated usign a Monte Carlo simulation. The results show that combining...

Topics: DTIC Archive, Dinger,R J, NAVAL WEAPONS CENTER CHINA LAKE CA, *Scintillation, *Radar targets,...

The objective of this project was to establish the theoretical foundations for applying higher order Rayleigh and interface modes to resonators for high stability sensors. Theoretical studies of the characteristics of Rayleigh waves in single and multi-layer structures were carried out for ST-cut Quartz substrates. Specified materials for this study were MgO, Y2O3, AlN, SiOx, Al2O3, and TiO2. Velocity dispersion and coupling to bulk modes were predicted and confirmed by comparison with...

Topics: DTIC Archive, Staples, Edward J, AMERASIA TECHNOLOGY INC WESTLAKE VILLAGE CA, *RAYLEIGH WAVES,...

Partial Contents: Source and Propagation Effects of Rayleigh Waves from Central Asian Earthquakes--Abstract of Doctoral Thesis; Three-Dimensional Crust and Upper Mantle Structure of the Northeastern United States; The Attenuation of Seismic Waves in Dry and Saturated Rocks; Thermal Cracking and Amplitude Dependent Attenuation; and Ultrasonic P and S Wave Attenuation in Dry and Saturated Rocks under Pressure.

Topics: DTIC Archive, Patton, Howard, ARMY ENGINEER COMMAND VIETNAM APO SAN FRANCISCO 96491, *SEISMIC...

We consider the problem of reconstructing the flexural rigidity r(x) and the density rho(x) of a beam. The unknown beam is assumed to have a free left end and a clamped right one. The data consist of the displacement and angle of the center line of the free left end following an initial impulse. The information content of this seismogram-like impulse response is equivalent to three spectra (omega sub n), (nu sub n), (mu sub n) and two gross constants F1, F2. This data do not specify the...

Topics: DTIC Archive, Barcilon, Victor, CHICAGO UNIV IL DEPT OF GEOPHYSICAL SCIENCES, *MATHEMATICAL MODELS,...

Goda's (1975) model, describing wave transformation from deep water to across the surf zone, is compared with a large amount of wave data obtained from experiments conducted at Torrey Pines Beach, San Diego, California. Goda's model simulates wave breaking by truncating the Rayleigh distribution in order to estimate the wave height distributions across the surf zone; wave heights are shoaled by applying nonlinear theory. Comparisons between the empirical distributions and theoretical...

Topics: DTIC Archive, Teran,Galo Padilla, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *WATER WAVES,...

Large temperature gradients applied to a snow cover drive water vapor upward and result in rapid recrystallization of snow crystals. The same temperature gradients create gradients of air density that can cause flows of air through the snow cover. This report develops formalism necessary to describe these flows in an effort to include the convection of vapor in the understanding of snow metamorphism. The theory of convection through porous media is extended to include the transport of water...

Topics: DTIC Archive, Powers,D J, COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH, *SNOW,...

The research summarized concerns four topics of the propagation and scattering of acoustical and optical waves: Acoustical scattering theory and experiments (focused backscattering from elastic spheres due to Rayleigh waves and resonances, Sommerfeld-Watson transformation or predicting echo amplitudes and resonance phenomena, scattering from complicated elastic objects); Novel manifestations of diffraction catastrophes and their application to invese problems (optical hyperbolic-umbilic and...

Topics: DTIC Archive, Marston, Philip L, WASHINGTON STATE UNIV PULLMAN DEPT OF PHYSICS, *ACOUSTIC...

The goals of this thesis are (1) to design and test a two-axis surface wave source and two-axis surface wave receiver and (2) to investigate the use of surface waves to detect buried objects in water saturated sand. Results of measurements confirm the ability to generate particle motions in water saturated sand consistent with surface wave excitation. However, limitations in the size of the test tank prohibit a thorough investigation of the ability of the source and receiver to selectively...

Topics: DTIC Archive, Anglin, Anthony J., NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *MINE DETECTION, *RAYLEIGH...

An acousto-elastic method was developed to estimate the residual stress and texture of a flat metal surface by simultaneous measurement of Rayleigh waves and surface skimming longitudinal waves (or P waves). The method showed promise in the successful recovery of surface residual stress in an AA 7076-T651 aluminum sample surface-treated by low plasticity burnishing. The effects of sandblasting and shot peening on a commercially pure titanium, a Ti-6Al-4V titanium alloy, and two Al-Cu aluminum...

Topics: DTIC Archive, Man, Chi-Sing, KENTUCKY UNIV LEXINGTON, *SURFACE WAVES, *RESIDUAL STRESS, *TEXTURE,...

This paper describes an experiment to demonstrate for the first time, laser wakefield acceleration (LWFA), driven by 1O.6-micrometer light from a CO2 laser. This experiment is also noteworthy because it will operate in a pseudoresonant LWFA regime in which the laser-pulse-length is too long for resonant LWFA, but too short for self-modulated LWFA. Nonetheless, high acceleration gradients are still possible. This experiment builds upon an earlier experiment called staged electron laser...

Topics: DTIC Archive, NAVAL RESEARCH LAB WASHINGTON DC, *CARBON DIOXIDE LASERS, LASER APPLICATIONS, RAMAN...

The authors investigate the application of two numerical methods (finite element and finite difference approximations) toward the ultimate solution of problems involving the propagation of Rayleigh waves generated by an explosion in the atmosphere over an island atoll. Because of mathematical difficulties in these methods, useful calculations of Rayleigh wave spectra at teleseismic distances were not obtained. It appears that the physical constraints of the atoll structure, e.g., abrupt changes...

Topics: DTIC Archive, McCowan, D W, TELEDYNE GEOTECH ALEXANDRIA VA ALEXANDRIA LABS, *NUCLEAR EXPLOSIONS,...

Analysis of eight 80-minute noise samples, recorded during the period 29 March to 7 October 1967, has been completed. Four of these samples were recorded consecutively thereby forming a 320 minute long noise sample. The analysis includes power density spectra, multiple coherencies, and wavenumber spectra. In general, the summer noise appears similar in character to previously analyzed winter noise samples. The only usable microbarographic data was recorded by an instrument located within 50...

Topics: DTIC Archive, Binder, Frank H, TEXAS INSTRUMENTS INC DALLAS SCIENCE SERVICE DIV, *SEISMOLOGICAL...

Turbo product codes (TPC) are a promising approach for power-efficient communications, particularly in satellite and terrestrial wireless systems. These codes use an iterative decoding method similar to turbo codes. TPCs have been shown to have a bit error rate (BER) performance within a couple of dB of turbo codes without the error floor, however other performance measures of turbo product codes are not well developed. This thesis applies the Extrinsic Information Transfer (EXIT) chart...

Topics: DTIC Archive, Durham, Laura M, MASSACHUSETTS INST OF TECH CAMBRIDGE DEPT OF ELECTRICAL ENGINEERING...

During the final year of our project, we have calibrated the use of surface-wave magnitudes (Ms), measured at regional distances as a rapid and robust estimator of seismic moment. We have used the Russell (2006) variable period surface-wave magnitude formula to convert Ms to seismic-moment magnitude, Mw, at local to regional distances using global datasets. In this pilot study, the Russell Ms technology was applied to 169 North American events with 3.2 Mw 6.5 at distances ranging from 48 to...

Topics: DTIC Archive, WESTON GEOPHYSICAL CORP LEXINGTON MA, *CALIBRATION, *SCALE, *SEISMIC WAVES,...

The correct identification and association of Rayleigh waves is vital within the context of the CTBT because of the use of the body-wave to surface wave magnitude ratio m(b):M(s) as a discrimination method. Rayleigh waves can be identified by their dispersion characteristics (the variation in group speed with frequency) and their elliptical polarization in the plane of propagation. Classically, Rayleigh waves are associated with a seismic disturbance by calculating the angle from which the wave...

Topics: DTIC Archive, MINISTRY OF DEFENCE READING (UNITED KINGDOM), *IDENTIFICATION, *RAYLEIGH WAVES,...

Topics: DTIC Archive, O'Connor, J J, PRATT AND WHITNEY AIRCRAFT GROUP EAST HARTFORD CT, *AIRFRAMES,...

Phase-matched filters are defined as a class of linear filters in which the Fourier phase of the filter is made equal to that of a given signal. An interative technique is described which can be used to find a phase-matched filter for a particular seismic signal. The process is then applied to digital records of Rayleigh waves from a synthetic source with propagation across 55 deg. of continental path, an earthquake in the Greeland Sea Recorded in Texas, and a nuclear explosion in Novaya Zemlya...

Topics: DTIC Archive, Herrin, Eugene, SOUTHERN METHODIST UNIV DALLAS TX DALLAS GEOPHYSICAL LAB, *SEISMIC...

Contents: Spectral characteristics of the Lg wave generated by Central U.S. earthquakes; Ground motion modelling at regional distances for earthquakes in a continental interior; Regional Rayleigh wave attenuation in North America; Surface wave attenuation in Eurasia; Radiation from shallow focus earthquakes in the Sakhalin and Kurile Islands.

Topics: DTIC Archive, Stauder, William, SAINT LOUIS UNIV MO DEPT OF EARTH AND ATMOSPHERIC SCIENCES,...

Several characteristics of oceanic surface waves can be altered by low rigidity sediments along the propagation path. Specifically spectral shape of both Love and Rayleigh waves as well as path phase velocity can be affected. The theoretical Love wave spectra is sensitive to both the nature of the low velocity zone and the sediment structure. Thus, observed Love wave spectra do not constrain focal depth.

Topics: DTIC Archive, Weidner, Donald J, STATE UNIV OF NEW YORK AT STONY BROOK DEPT OF EARTH AND SPACE...

We present new maps of Lg coda Q and its frequency dependence at 1 Hz (Qo and eta, respectively) as well as Rayleigh-wave attenuation coefficients at 5, 10, 20 and 50 s across virtually all of Eurasia. Qo is relatively high, 700 or more, in most cratonic regons but is surprisingly low in the Arabian craton (300-450), the Siberian trap portion of the Siberian Platform (450) and the Deccan trap portion of the Indian Platform(450-650). It is generally low throughout the Tethysides orogenic belt...

Topics: DTIC Archive, Mitchell, Brian J, SAINT LOUIS UNIV MO, *EURASIA, *RAYLEIGH WAVES, *MULTIPLICATION...

The crust of southern Eurasia is characterised by low Q values (200-450) for 1-Hz Lg coda everywhere from Spain to China. The north-south extent of that low-Q zone varies from being relatively narrow in western Europe to being very broad from the Middle East to China. Those variations in both magnitude and width first became apparent with the development of continent-wide tomographic maps of Lg coda Q. The most recent mappings of Lg coda Q values at 1 Hz, completed over the past year, show that...

Topics: DTIC Archive, Cong, Lianli, SAINT LOUIS UNIV MO OFFICE OF RESEARCH SERVICES, *SEISMIC WAVES,...

An automated, computer controlled goniometer was constructed and perfected. Controlled measurements on a variety of materials, including materials of interest to the NDT community, were carried out and compared with theoretical predictions made by a number of authors. Experimental results indicate that these theories may be only first approximations to reality. A number of significant experimental anomalies, such as the appearance of more than one amplitude dip were found. Certain theoretical...

Topics: DTIC Archive, Hildebrand,B P, SPECTRON DEVELOPMENT LABS INC COSTA MESA CA, *Nondestructive testing,...

This document discusses the initial value problem in one-dimensional linear visco-elasticity with a step-jump in the initial data. If the memory kernel is sufficiently smooth on (infinity), the solution exhibits discontinuities propagating along characteristics and a (higher order) stationary discontinuity at the position of the original step-jump. For a singular memory kernel, the propagating waves are smoothed in a manner depending on the nature of the singularity in the kernel, but the...

Topics: DTIC Archive, Hrusa,W J, WISCONSIN UNIV-MADISON MATHEMATICS RESEARCH CENTER, *VISCOELASTICITY,...

High data rate communication links operating under slow fading channel conditions may have interleaving memory requirements which are too large for practical applications. These requirements can be reduced by employing spacial diversity; however, a less costly alternative is to select coding and interleaving techniques that support memory efficient interleaving. The objective of this investigation has been to find coding and interleaving techniques with relatively small interleaving memory...

Topics: DTIC Archive, Strater, Jay W, MISSION RESEARCH CORP SANTA BARBARA CA, *REQUIREMENTS, MEMORY...

The primary objective of this work has been to map the variations of elastic mantle properties beneath Eurasia over horizontal length scales of approximately 1000-1500 kilometers and vertial length scales of 50-100 kilometers in the upper mantle. Large and diverse datasets of seismic waveforms, absolute and relative body wave travel times, and surface wave phase velocity and amplitudes have been collected and have been analyzed. Several tens of thousands of measurements of intermediate period...

Topics: DTIC Archive, Ekstrom, Goran, HARVARD UNIV CAMBRIDGE MA, *SEISMIC DATA, *EARTH MOVEMENTS, *EARTH...

In this study we investigate the inversion of long period regional waveforms for moment tensors with particular emphasis on aspects important for monitoring. We begin with moment tensor inversions for the September 14, 1988 US-Soviet Joint Verification Experiment (JVE) nuclear test at the Semipalatinsk test site in Eastern Kazakhstan, and several nuclear explosions conducted less than ten years later at the Chinese Lop Nor test site. The events are very sparsely recorded with only several...

Topics: DTIC Archive, CALIFORNIA UNIV BERKELEY, *SEISMIC DISCRIMINATION, *TENSOR ANALYSIS, DATA PROCESSING,...

Wireless systems, including wireless local area networks (WLAN) and cellular networks, are increasingly being used for both commercial and military applications. For military applications, it is important to analyze the effect of interference on wireless communications systems. The objective of this research is to investigate the performance of variable code rate signals transmitted over frequency-nonselective, slowly fading channels in a worst case, pulse-noise interference environment. Both...

Topics: DTIC Archive, Shih, Wan-Chun, NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF ELECTRICAL AND COMPUTER...

Rayleigh's criterion states that a pair of point sources are barely resolved by an optical instrument when the central maximum of the diffraction pattern due to one source coincides with the first minimum of the pattern of the other source. As derived in standard introductory physics textbooks,1 the first minimum for a rectangular slit of width a is located at angular position theta = sin(inverse) (lambda /a) for light of wavelength lambda. If the angular separation of the two sources is small,...

Topics: DTIC Archive, NAVAL ACADEMY ANNAPOLIS MD DEPT OF PHYSICS, *NUMERICAL APERTURE, *RAYLEIGH WAVES,...

This report describes the results of a continuing investigation of the characteristics of the low frequency ground motions produced by atmospheric explosions. The studies reported here have focused on two aspects of this problem: (1) the full-scale validation of nuclear tests, and (2) the preliminary evaluation of a theoretically-based prediction methodology. With regard to the validation study, the mathematical model has been applied to the theoretical simulation of ground motion data recorded...

Topics: DTIC Archive, Murphy,J R, S-CUBED LA JOLLA CA, *AIRBURST, *SEISMIC DETECTION, *NUCLEAR EXPLOSION...

Combined matched filtering and array summing methods have been developed that yield improved spectral estimates for weak surface waves. Both theoretically and experimentally the best spectral estimates are obtained by first beaming an array of individual matched filtered seismograms and then computing a single noise-corrected spectrum. Spectral results for test cases and actual events are compared using three different techniques. Computer programs implementing these spectral methods have been...

Topics: DTIC Archive, Lambert, John W, TELEDYNE GEOTECH ALEXANDRIA VA SEISMICDATA LAB, *UNDERGROUND...

Results relating to the analytical modeling of earthquakes by relaxation-source theory models are summarized. Applications to explosion- earthquake discrimination and earthquake source parameter estimation, particularly tectonic stress determinations, are discussed in detail. The theoretical work summarized includes: generalized representation theorems, energy considerations, equivalence theory, radiation field solutions for relaxation models of earthquakes, computer based earthquake field...

Topics: DTIC Archive, Archambeau, Charles B, COLORADO UNIV AT BOULDER, *EARTHQUAKES, *SEISMIC DETECTION,...

The main goal of this project is to develop models of lithospheric velocity structure for Eurasia and the Middle East in order to improve capabilities within National Nuclear Security Administration (NNSA) labs to accurately predict travel times for local and regional phases, as well as travel-times for body waves at upper-mantle triplication distances. Velocity models of the lithosphere are key for accurately modeling not only travel times but also surface-wave dispersion velocities and full...

Topics: DTIC Archive, PENN STATE RESEARCH FOUNDATION UNIVERSITY PARK PA, *LITHOSPHERE, EURASIA, MIDDLE...

A deephole array consisting of 12 short-period triaxial seismometers was operated at a test site near Grapevine, Texas (GVTX) until 23 February 1968. The system was then put in a standby status until additional software could be developed to provide additional filtering capabilities. The complete system was shut down and all of the instrumentation and equipment was moved into storage areas at the Geotech plant in Garland, Texas, during the last week of May. The information gathered from the...

Topics: DTIC Archive, Der, Zoltan A, GEOTECH GARLAND TX, *SEISMOLOGICAL STATIONS, *UNDERGROUND EXPLOSIONS,...

A collection of new findings are presented contributing to fundamental physical understanding of broadband (3-500 KHz) transient seismoacoustic wave phenomena in various sand conditions (water-saturated, naturally settled, disturbed, drained, liquefied, compacted, water-covered, air bubbles) important for acoustic modeling of seafloor and predicting the penetration and conversion of seismoacaoustic waves in sediments. The experimental results compare waveforms of different types of...

Topics: DTIC Archive, Chamuel, Jacques R, SONOQUEST ADVANCED ULTRASONICS RESEARCH WELLESLEY HILLS MA,...

The performance of digital communications over selective wide-sense-stationary uncorrelated-scattering (WSSUS) fading channels is investigated. The emphasis is on the evaluation of the performance of binary differential phase-shift keyed (DPSK) and binary frequency-shift keyed (FSK) communications with primary emphasis on the effects of intersymbol interference produced by the frequency-selective character of WSSUS fading channels. The error probabilities of DPSK and FSK are evaluated for...

Topics: DTIC Archive, Garber,F D, ILLINOIS UNIV AT URBANA COORDINATED SCIENCE LAB, *COMMUNICATION...

Rayleigh wave velocities were measured for broad band noise excitation of ground surfaces. Two noise sources were used: a vibrator using band-passed filtered white noise and a hammer drop for impulses. The Rayleigh wave velocities were computed using Fourier analysis to determine phase differences between transducers located a fixed distance apart. Measurements with the impulsive source agreed with the vibrator measurements and showed good results for Rayleigh wave velocities over wide...

Topics: DTIC Archive, Williams,Otis, ARMY ENGINEER WATERWAYS EXPERIMENT STATION VICKSBURG MS ENVIRONMENTAL...

The objective of the work presented here is to develop and evaluate the adequacy of an elastic source description of the near-in surface recordings of ground motion from the underground nuclear test 'Milrow'. Generalized ray, mode and discrete wavenumber techniques have been applied to model four of the available vertical and radial L-7 records. Preliminary results indicate that an elastic description will be adequate for distances greater than 7 km. No clear azimuthal trends are manifest in...

Topics: DTIC Archive, Cole, David M, WOODWARD-CLYDE CONSULTANTS PASADENA CA, *NUCLEAR EXPLOSION TESTING,...

This thesis investigates the performance degradation resulting from multitone interference of orthogonal, noncoherent, frequency-hopped, M-ary frequency-shift keyed receivers (FH/MFSK) where the effect of thermal and other wideband noise is not neglected. The multiple, equal power jamming tones are assumed to correspond to some or all of the possible FH M-ary orthogonal signaling tones. Furthermore, the channel is modeled as a Ricean fading channel, a possibility precluded when thermal noise is...

Topics: DTIC Archive, Katsoulis, George T., NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *ELECTRONIC COUNTER...

Regional seismograms from the Soviet JVE explosion were modeled. The explosion part of the source contained considerable RDP overshoot with possible spall contribution. The tectonic release part was composed of stress relaxation and secondary high frequency sources. Pn, Sn, Rayleigh and Love waves were modeled. SsPmp phases were discovered in regional waves and modeled using ray theory and synthetic seismogram computations. SsPmp is an important wave in broadband data for event under the...

Topics: DTIC Archive, Langston, Charles A., PENNSYLVANIA STATE UNIV UNIVERSITY PARK DEPT OF GEOSCIENCES,...

An investigation of scattering from surface cracks has been conducted. In particular, the change in the reflection coefficient of a Rayleigh wave incident on a surface indentation crack has been measured as the sample is stressed to fracture. The acoustic measurements have been correlated with the stable crack extension that precedes final failure. The crack extension behavior in as-intended and annealed specimens was found to be appreciably different. The cracks in the annealed samples...

Topics: DTIC Archive, Tien,J J W, STANFORD UNIV CA EDWARD L GINZTON LAB OF PHYSICS, *CERAMIC MATERIALS,...

An investigation of scattering from surface cracks has been conducted. In particular, the change in the reflection coefficient of a Rayleigh wave incident on a surface indentation crack has been measured as the sample is stressed to fracture. The acoustic measurements have been correlated with the stable crack extension that precedes final failure. The crack extension behavior in as-intended and annealed specimens was found to be appreciably different. The cracks in the annealed samples...

Topics: DTIC Archive, Tien,J J W, STANFORD UNIV CA EDWARD L GINZTON LAB OF PHYSICS, *CERAMIC MATERIALS,...

We consider the problem of reconstructing the flexural rigidity r(x) and the density rho(x) of a beam. The unknown beam is assumed to have a free left end and a clamped right one. The data consist of the displacement and angle of the center line of the free left end following an initial impulse. The information content of this seismogram-like impulse response is equivalent to three spectra (omega sub n), (nu sub n), (mu sub n) and two gross constants F1, F2. This data do not specify the...

Topics: DTIC Archive, Barcilon, Victor, CHICAGO UNIV IL DEPT OF GEOPHYSICAL SCIENCES, *MATHEMATICAL MODELS,...

Seismic surface waves are usually composed of overlapping wave trains representing multi-path propagation. A first task in the analysis of such waves is to identify and separate the various component wave trains so that each can be analyzed separately. Phase-matched filters are a class of linear filters in which the Fourier phase of the filter is made equal to that of a given signal. The authors previously described an iterative technique which can be used to find a phase-matched filter for a...

Topics: DTIC Archive, Herrin, E, SOUTHERN METHODIST UNIV DALLAS TX DALLAS GEOPHYSICAL LAB, *LINEAR...

We continue to develop and test the Matlab program EVALSURF, which estimates variable-period (8 less Tau less than 25 sec) Rayleigh-wave magnitudes using the Russell (2006) and M(s) (VMAX) measurement technique (Bonner et al., 2006a) for comparison to the historical formulas of Marshall and Basham (1972) and Rezapour and Pearce (1998). The program uses the updated Lawrence Livermore National Laboratory (LLNL) group velocity models (Pasyanos, 2005) to identify, phase match filter, and extract...

Topics: DTIC Archive, LAWRENCE LIVERMORE NATIONAL LAB CA, *COMPUTERIZED SIMULATION, *NUCLEAR EXPLOSIONS,...

The purpose of this study is to improve group velocity maps designed to advance the detection and discrimination capabilities for the area encompassed by western China, northern India, and Pakistan. These maps may be used to construct sharply tuned phase-matched filters for extracting weak surface wave signals from background noise and to make better estimates of surface wave spectral magnitudes for small events. We are working now to obtain a greatly expanded data set of short-period...

Topics: DTIC Archive, COLORADO UNIV AT BOULDER, *GROUP VELOCITY, *PERIODIC VARIATIONS, *ASIA, *SHORT...