bluuebunny/crossref_metadata_2025_split huggingface dataset:
Causes of regional variation of magnitudes
Authors: Ward Ronald W. , Toksöz M. Nafi 
Published: September 2021

abstract
Data from the short and long-period seismographs at the NORSAR in Norway are used to investigate the discrimination of earthquakes and underground nuclear explosions using surface-wave versus body-wave magnitude (Ms versus mb). Earthquakes and explosions occurring within the western United States and recorded in Norway exhibit either anomalously large surface waves or anomalously low compressional body waves compared to events from central Asia. These data, as well as the results of other investigators, indicate an anomaly of 0.8 to 1.0 in Ms or 0.6 to 0.8 in mb or some linear combination of the two. The mechanism producing anomalously large Ms values from a region for explosions and the cause of lower mb values are investigated in terms of stress relaxation triggered by an explosion and regional variations in attenuation in the upper mantle beneath both the source region and the receiver region.
The method of short-period amplitude spectral ratio is applied to the records of the waves from five deep events to determine the difference in attenuation beneath different receivers. The relative Q model inferred from these data for the upper mantle from 50 to 750 km depth is QLASA = 75, QTFSO = 175, and QNORSAR = 390. The circum-Pacific island arc exhibits an apparent source attenuation asymmetry. The data from the mid-Atlantic ridge indicate that strong attenuation may be associated with parts of the ridge.
The relative difference of the Q model between LASA and NORSAR results in a difference in mb of 0.40 for distances of 60° to 80°, which agrees well with the observed differences in mb. We conclude that regional variations of attenuation in the upper mantle play an important role in regional differences in Ms versus mb relationship.
Elastic-wave propagation in two evenly-welded quarter-spaces
Authors: Ottaviani Mario 
Published: September 2021

abstract
This paper deals with elastic-wave propagation in two evenly-welded quarter-spaces. A compressional line source can be located at any point within either medium. The numerical solutions to this problem have been obtained by using the finite difference method. A computer program has been written to obtain synthetic seismograms of the horizontal and vertical displacements at all nodes of the superimposed grid, for the following cases: (a) elastic-wave propagation in a quarter-space, and (b) elastic-wave propagation in two quarter-spaces.
Reflected, converted, transmitted, and diffracted phases are identified and interpreted. Surface and interface waves, originated at the corner by diffraction of the source pulse, are investigated as a function of the rigidity contrast and the velocity contrast between the two media and of the position of the source.
Two-dimensional seismic modeling techniques have been used to provide a qualitative experimental verification of the numerical results.
Experimental determination of the dynamic properties of a bridge substructure
Authors: Shepherd R. , Charleson A. W. 
Published: September 2021

abstract
As part of an investigation of the dynamic properties of bridge substructures, a series of steady-state vibration tests were undertaken on a multispan continuous deck bridge at several stages during construction. In this paper the method of testing is outlined and the measured natural frequencies and derived values of equivalent viscous damping are presented. The results confirm that the bridge does behave in a manner reasonably consistent with the design assumptions. At the small values of vibration amplitude generated, an equivalent viscous damping of the order of 4 per cent of critical was determined for the completed bridge.
The relationship between two- and three-dimensional elastic-wave propagation
Authors: Dampney C. N. G. 
Published: September 2021

abstract
A technique similar to inverting Abel's equation is used to invert the descent of dimensions method between three-dimensional, cylindrically-symmetric and two-dimensional wave propagation. The end result is a very simple relationship between the two types of wave propagation. Apart from its intrinsic interest, the large number of two-dimensional studies reported in the literature could now be related to their three-dimensional counterparts.
Travel-time errors in the laterally inhomogeneous earth
Authors: Lomnitz Cinna 
Published: September 2021

abstract
Travel times from earthquakes or explosions contain both positive and negative systematic errors. Positive skews in travel-time residuals due to epicenter mislocation, and negative skews due to lateral inhomogeneity in the Earth, are analyzed. Methods for travel-time estimation are critically reviewed. Recent travel-time tables, including the J-B tables, are within the range of root-mean-square travel-time fluctuations; the J-B tables are systematically late but cannot be reliably improved by least-square methods. Effects of lateral inhomogeneity at teleseismic distances can be estimated by chronoidal methods independently of standard tables, but the available explosion data are insufficiently well-distributed in azimuth and distance for this purpose.
Seismic characteristics of underground nuclear detonations
Authors: Mueller Richard A. , Murphy John R. 
Published: September 2021

abstract
A seismic-spectrum scaling model based on an analytic approximation to the nuclear seismic-source function is described and evaluated in terms of the behavior of a large body of measured spectral data. The results of the scaling analysis indicate that the yield, depth of burial and emplacement medium of the nuclear device play significant roles in defining the seismic-spectrum scaling of underground nuclear detonations. Results are presented which indicate that cube-root-yield scaling of the nuclear seismic-source function is not appropriate. For events buried sufficiently deep for containment, the scaling theory predicts frequency-dependent yield exponents ranging from 0.90 at low frequencies to 0.45 at high frequencies. These yield-scaling exponents are in good agreement with empirical relations statistically derived from measured data.
Seismic characteristics of underground nuclear detonations
Authors: Murphy John R. , Mueller Richard A. 
Published: September 2021

abstractAn expression is derived for the elastic energy produced by a contained, underground nuclear detonation using an analytic approximation for the pressure profile acting at the elastic radius. The resulting static strain energy and radiated energy equations are evaluated as a function of yield and depth of burial for detonations in tuff and rhyolite. It is shown that, for a given medium, the elastic-energy efficiency depends only on the depth of burial (h) of the device and is proportional to h0.72. Moreover, for the particular scaling relations used, the strain energy shows the same depth dependence as the radiated energy. Seismic-spectrum scaling theory is applied to an analysis of nuclear seismic-source functions, giving results which are in good agreement with the observed differences in the teleseismic magnitude determinations. A magnitude-energy equation is derived for underground nuclear detonations and is noted to be in poor agreement with the Gutenberg-Richter equation. This discrepancy is interpreted to be an indication that the radiated energy from small earthquakes may typically have been underestimated.
A method for synthesizing realistic strong ground motion
Authors: Trifunac Mihailo D. 
Published: September 2021

abstract
A new method of synthesizing artificial accelerograms, based on knowledge of the temporal and spatial properties of the energy-release mechanism, incorporates the effects of local geology through theoretical group-velocity dispersion data for a given site. It is assumed that most of the near-field strong ground motion caused by shallow or surface faulting or explosions is represented by energy propagating through the low-velocity surface-wave guide. The new method of generating artificial accelerograms realistically models strong ground motion for applied structural analysis and theoretical investigations of the response of hysteretic-type structures, soil-structure interaction, and statistics of failure.
A seismic discriminant based on focal mechanism
Authors: Syed Atiq A. , Kisslinger Carl , Nuttli Otto W. 
Published: September 2021

abstract
Utilizing the observation that a predominant focal mechanism exists for a given hypocentral region, a seismic discriminant based on body-wave magnitude has been developed. This discriminant enables one to identify earthquakes that do not fit mechanisms expected from plate tectonics. It also sorts out explosions as anomalies, even for those regions in which the focal mechanism results in compressional first motions at most or all available seismograph stations.
The relationship between teleseismic body-wave magnitude m and local magnitude ML from New Zealand earthquakes
Authors: Gibowicz S. J. 
Published: September 2021

Abstract
Relationships between the magnitudes ML and m for 123 New Zealand earthquakes occurring between 1950 and 1967 and having 4.6 ≦ ML ≦ 7.3 have been found. Deep- and shallow-focus shocks were considered separately. There is a linear relationship between ML and m, the slope being the same for both deep and shallow events. Values of ML for deep events are consistently 0.5 magnitude larger than those for shallow events having the same value of m. The relationship between m and ML for New Zealand earthquakes differs significantly from that obtained by Gutenberg and Richter in California.
Evidence for the existence of locally-generated body waves in the short-period noise at the Large Aperture Seismic Array, Montana
Authors: Iyer H. M. , Healy John H. 
Published: September 2021

Abstract
The approximate hexagonal configuration of LASA subarrays enables their use as omnidirectional arrays. This property is used to study the phase velocity of short-period seismic noise at different frequencies. It is found that the noise in the low-frequency band consists mainly of surface waves traveling with average velocities in the range 3.0 to 3.5 km/sec. The high-frequency noise, in the band 0.45 to 1.0 Hz, has an average velocity of about 6.0 km/sec. It is quite likely that the high-frequency noise has the nature of locally-generated body waves. Statistical analysis of Pg velocities observed during a crustal refraction experiment at LASA lends support to this hypothesis.
Interaction of a shear wall with the soil for incident plane SH waves
Authors: Trifunac M. D. 
Published: September 2021

Abstract
The closed-form solution of the dynamic interaction of a shear wall and the isotropic homogeneous and elastic half-space, previously studied only for vertically-incident SH waves, is generalized to any angle of incidence. It is shown that the interaction equation is independent of the incidence angle, while the surface-ground displacements heavily depend on it. For the two-dimensional model studied, it is demonstrated that disturbances generated by waves scattering and diffracting around the rigid foundation mass are not a local phenomenon but extend to large distances relative to the characteristic foundation length.
Residuals and velocities of Pn waves recorded by the San Andreas seismograph network
Authors: Kind Rainer 
Published: September 2021

Abstract
Travel-time residuals were calculated for Pn arrivals from four nuclear explosions and 10 earthquakes recorded by the U.S. Geological Survey's San Andreas seismic telemetry network. Arrivals at stations west of the fault are earlier than at stations east of the fault. Stations on basement rocks indicate a variation in crustal thickness of about 5 to 9 km across the fault at the center of the network. The average mantle velocity after correcting for the residuals is 8.0 km/sec. The Pn waves traveling from the east, when corrected for crustal delay, have a velocity of 7.7 to 7.8 km/sec. Waves traveling from the north or south, after the same corrections, have a Pn velocity of 8.0 to 8.2 km/sec. This difference may be caused by an anisotropic upper mantle, but additional data from seismic sources in the Pacific will be required to confirm this result.
Residual dispersion measurement—a new method of surface-wave analysis
Authors: Dziewonski A. , Mills J. , Bloch S. 
Published: September 2021

Abstract
Measurements of group velocities by means of band-pass filtering lead to systematic errors when group in velocity changes rapidly with frequency. A new method hereafter referred to as “residual dispersion measurement” avoids this difficulty by transforming the signal prior to the filtering. An observed seismogram is cross-correlated with a theoretical seismogram in which the dispersion approximates the observed dispersion within a few per cent. Dispersion of the resulting pulse can be measured with a much higher precision, since du/dω has been reduced by at least an order of magnitude. In addition, the method can be employed iteratively to obtain a greater precision of measurement.
The dispersion of mantle Rayleigh waves is measured from a sum of 48 auto-correlograms of the recordings of the Alaskan earthquake of March 28, 1964. Group and phase velocities are obtained for order numbers between 0S9 and 0S47. It is estimated that the absolute error of the group-velocity measurement does not exceed 0.015 km/sec.
The analysis of a sum of 13 auto-correlograms of horizontal component seismograms with predominantly transverse motion reveals that the fundamental-mode Love-wave data may be contaminated by higher torsional modes. Comparison of several sets of average Love-wave phase velocities shows a discrepancy of the order of 0.4 per cent in the period range from 350 to 170 sec. The corresponding figure for Rayleigh waves is less by at least an order of magnitude.
Response spectrum solution for earthquake analysis of unsymmetrical multistoried buildings
Authors: Gibson R. E. , Moody M. L. , Ayre R. S. 
Published: September 2021

Abstract
Modal analysis and response spectra are use to develop an approximate method for earthquake analysis of unsymmetrical multistoried buildings modeled as shear-flexible cantilever beams. The beam has constant mass per unit length and a linear variation of elastic shearing resistance along its length. Existing modal solutions are used and response spectra for two horizontal earthquake components are included in the analysis. Solutions for a typical building are presented and compared with an exact form of solution.
Complex roots of the Stoneley-wave equation
Authors: Pilant Walter L. 
Published: September 2021

Abstract
The equation governing elastic waves propagating along a solid-solid interface is found to have sixteen (16) independent roots on its eight (8) associated Riemann sheets. The range of existence (in terms of material parameters) for the real root corresponding to the propagation of Stoneley waves has long been known. It is found that outside this range there are two types of behavior. If the material of greater density has a velocity slightly greater than that of the material of lesser density, the unattenuated Stoneley waves make a transition to attenuated Interface waves, i.e., they leak energy away from the interface as they propagate along it. If the more dense material has a velocity more than about three times that of the less dense, then the Interface-wave root disappears and energy is propagated along the interface as Rayleigh waves. This Rayleigh-wave propagation is associated with a different root of the fundamental equation. On the other hand, if the material of greater density has a velocity much lower than that of the material of lower density (a case that is difficult to find physically), then no energy will be propagated along the interface at all. This result was unexpected. Some rather interesting behavior of the 16 roots was noted as the physical parameters were varied over a wide range. In addition to the normal collisions between pairs of roots, and between individual roots and branch points (with attendant Riemann sheet jumping), it was found that some roots go through the point at infinity and return with a change in sign. At least one unexpected case of a multiple root was found. Another case was noted in which a pair of complex roots change quadrants in the complex phase-velocity plane, leading to a discontinuity in root type. Finally, it was noted that, in a cyclic variation of the material parameters, it is possible to choose a path such that the roots, when followed individually, will not return to their original values. In fact, as many as five cycles in parameter space can be accomplished before the roots return. All this strange mathematical behavior seems to have no physical significance, but has been presented to increase understanding of the general behavior of the dispersion relations associated with elastic-wave propagation.
Highrise building characteristics and responses determined from nuclear seismology
Authors: Blume John A. 
Published: September 2021

abstract
Reliable measurements and detailed analyses of the responses of many buildings to ground motion resulting from underground nuclear explosions are providing new and valuable information on the structural-dynamic properties and behavior of real buildings. Much, if not all, of this knowledge is applicable to the problem of resisting natural earthquake ground motion, and it is being obtained as a byproduct of the AEC underground explosive nuclear safety program which is concerned with developing techniques for making reliable predictions of response and any damage.
Information is provided on oscillator spectral response values, building responses, modal contributions and combinations versus elapsed time and at times of maximum response, variations in natural periods, foundation material interaction, and biaxial motion in the horizontal plane. Data are shown for nuclear events JORUM and HANDLEY and then compared to those of prior major events. In addition, peak responses of certain Las Vegas buildings to the distant February 1971 San Fernando earthquake (U.S. Geological Survey, 1971) are provided and compared to responses to nuclear events.
Oceanic mantle phases recorded on seismographs in the Northwestern Pacific at distances between 7° and 40°
Authors: Sutton George H. , Walker Daniel A. 
Published: September 2021

abstract
Body-wave data recorded on hydrophones at Midway, Wake, and Eniwetok and on seismographs at Midway, Wake, and Marcus indicate the following for the mantle under the Northwestern Pacific Basin: a zone of low P-wave velocity with a thickness of about 75 km beginning in the uppermost 100 km of the Earth, perhaps very close to the M discontinuity; a wave guide immediately below the M discontinuity which propagates 3 to 8 Hz energies of compressional and shear phases with velocities of 8.28 ± 0.03 and 4.79 ± 0.04 km/sec, respectively, to great distances (observed to 33°, with the wave guide for compressional phases being considerably more efficient than the wave guide for shear phases); and, an asthenosphere of low Q for frequencies of 3 to 8 Hz as compared to that for material above and below.
Similar data for the East Caroline Basin-Ontong Java Plateau-Nauru Sea area indicate the following: a wave guide immediately below the M discontinuity which propagates 3 to 8 Hz energies of compressional phases with a velocity of 8.47 ± 0.48 km/sec to at least 22°; a weaker wave guide for shear phases than observed for the area to the north; an asthenosphere of low Q for frequencies of 3 to 8 Hz as compared to that for material above and below; and a velocity distribution somewhat different from that for the area to the north since, for normal refracted-mantle P phases recorded in the distance range of 22° to 40°, travel-time residuals are generally slightly negative for the area to the north and slightly positive for the area to the south.
Effects of site and propagation path on recorded strong earthquake motions
Authors: Lastrico Roberto M. , Duke C. Martin , Ohta Yutaka 
Published: September 2021

Abstract
Accelerograms from the 1952 and 1954 Kern County and the October 1933 Signal Hill earthquakes were used with detailed site models in an attempt to isolate the principal site, path, and source contributions in the recorded motions. Site models 20,000 ft deep were developed from soil, water and oil borings, geological reports, and near-surface refraction surveys at four accelerograph sites in Los Angeles and one at Taft, California. Analysis was based on linear system theory, using Fourier spectra and hypothesizing vertically incident shear waves.
The four subsurface site models at Los Angeles were adjusted within the uncertainties of the model properties to minimize the standard deviation of computed 1952 bedrock motions. These stations were close together relative to the epicentral distance. Resulting subsurface transfer functions showed, generally, highest amplifications at the Hollywood station and lowest at UCLA, with a 100 per cent range based on the latter.
Attenuation in the crustal path was evaluated using computed bedrock motions and incorporating the data at Taft. The exponent of distance for geometrical spreading was close to minus one. The damping along the path, expressed as Q, was 550 for the 1952 case and 62 for the 1933 case. A spectrum was obtained for the ratio of the source functions for the 1952 and 1954 earthquakes.
The connection between elastodynamic representation theorems and propagator matrices
Authors: Kennett B. L. N. 
Published: September 2021

Abstract
Two independent powerful methods in elastodynamics have been developed over the last few years: these are the use of representation theorems and propagator matrix techniques. The connection between these two approaches is derived in this paper. This is then used to show the equivalence of approximate techniques in elastic wave scattering based on representation theorems and a recent method based on matrix theory.
Distribution, focal mechanisms, and frequency of earthquakes in the Fairview Peak area, Nevada, near the time of the BENHAM explosion
Authors: Smith B. E. , Coakley J. M. , Hamilton R. M. 
Published: September 2021

Abstract
Six portable seismographs were operated for 30 days in a network centered 25 km south of the epicenter of the 1954 Fairview Peak earthquake. The recording period lasted from 15 days before to 15 days after detonation of the one-megaton BENHAM underground nuclear explosion 250 km to the southeast of the Nevada Test Site on December 19, 1968. Approximately 950 earthquakes were detected within about 30 km of the network. No evidence was found that the explosion affected the rate of earthquake occurrence. Locations were computed for 152 earthquakes. The epicentral pattern shows north and northeast trends about 1 to 3 km wide. Focal depths range from 5 to 14 km. The main zones of activity seem to have a near-vertical orientation. Composite fault-plane solutions suggest that faulting within zones is not consistent with a single focal mechanism. Instead, a variety of mechanisms is indicated, consisting primarily of north-striking right-lateral oblique-slip, and northeast-striking dip-slip movements. In both cases, the pressure axis is near vertical and the tension axis is near horizontal, striking about S60°E.