bluuebunny/crossref_metadata_2025_split huggingface dataset:
Source parameters of earthquakes, and discrimination between earthquakes and nuclear explosions
Authors: Davies John B. , Smith Stewart W. 
Published: July 2021

Abstract
The first part of this study describes a technique by which the source parameters of an earthquake can be obtained from the spectrum of compressional waves. The source parameters defined are fault length, fracture velocity, and fault plane attitude. Two large, deep earthquakes are examined using this technique. The source parameters determined compare favorably with those obtained previously using different techniques. In the second section a method is proposed for discrimination between underground explosions and earthquakes. The technique utilizes the ratio of the spectrums of the two classes of events where the path of propagation is common to both. On the basis of the analysis of the SHOAL event and a nearby shallow earthquake it appears that the duration as determined from the spectral ratio is almost 10 times smaller for an explosion than it is for a comparable earthquake.
Crustal characteristics from short-period P waves
Authors: Ellis R. M. , Basham P. W. 
Published: July 2021

Abstract
Thirty-four teleseismic events, recorded on the deep horizontal sediments of central Alberta, using one fixed and one movable station, have been analyzed as a test of the Haskell matrix formulation applied to short period P waves. Only limited agreement is obtained between averaged experimental vertical-horizontal spectral ratio curves and those calculated theoretically using known layer thicknesses and velocities.
Scattering in the crust and upper mantle is indicated by large transverse amplitudes including distict phases and by lower coherency for smaller epicentral distances where the travel path is confined to the crust and upper mantle. Anomalous SV/P ratios are believed to contribute to the difficulties. A study of 20 events in the azimuth range 285° to 310° indicates an apparent azimuth approximately 18° more northerly than the true azimuth. Localized dips of approximately 15° on the crustal boundaries are required to explain this deviation.
It is concluded that this region for which the sediments are horizontally layered does not fulfill the requirements of the Haskell matrix theory due to scattering and anomalous PS conversions in the crust and upper mantle.
Seismic source characteristics from explosion-generatedPwaves
Authors: Trembly Lynn D. , Berg Joseph W. 
Published: July 2021

ABSTRACTSignals from nuclear explosions were used to calibrate seismograph stations (near-regional, regional, and teleseismic ranges) by determining the transfer functions of the lumped source-propagation path-receiver systems. Recorded signals other than those used for calibration purposes were used to derive the characteristics of the sources. It was found that source functions could be derived from distant signals when the frequencies of the output signals were reliably related to the source. For the output data used in this research, the low-frequency cutoff was 0.2 cps at all stations and the high-frequency cutoffs were 4.0, 3.0, and 2.0 cps at the near-regional, regional, and teleseismic distances, respectively. The low-frequency cutoff was due mainly to the recording instruments, and the high-frequency cutoffs were due to the attentuation of the seismic energy by the Earth. The most reliable results were obtained when three half-cycles of the observed output signals (first arrivals) were used. When explosions in granite were used as calibration sources, the energies derived for explosions in tuff, alluvium, and dolomite media were 88, 65, and 12 per cent of the respective “observed” source energies.
P-wave travel times from shallow earthquakes recorded in India and inferred upper mantle structure
Authors: Kaila K. L. , Reddy P. R. , Narain Hari 
Published: July 2021

ABSTRACT
P-wave travel times of 39 shallow earthquakes and three nuclear explosions with epicenters in the North in Himalayas, Tibet, China and USSR as recorded in Indian observatories have been analyzed statistically by the method of weighting observations. The travel times from Δ = 2° to 50° can be represented by four straight line segments indicating abrupt velocity changes around 19°, 22° and 33° respectively. The P-wave velocity at the top of the mantle has been found to be 8.31 ± 0.02 km/sec. Inferred upper mantle structure reveals three velocity discontinuities in the upper mantle at depths (below the crust) of 380 ± 20, 580 ± 50 and 1000 ± 120 km with velocities below the discontinuities as 9.47 ± 0.06, 10.15 ± 0.07 and 11.40 ± 0.08 km/sec respectively.
The J-B residuals up to Δ = 19° are mostly negative varying from 1 to 10 seconds with a dependence on Δ values indicating a different upper mantle velocity in the Himalayan region as compared to that used by Jeffreys-Bullen in their tables (1940). Between 19° to 33° there is a reasonably good agreement between the J-B curve and the observation points. From Δ = 33° to 50° the J-B residuals are mostly positive with an average excess value of about 4 sec.
Large scale processing of seismic data in search of regional and global stress patterns
Authors: Ben-Menahem A. , Jarosch H. , Rosenman M. 
Published: July 2021

ABSTRACT
A composite compute program has been devised for a fast reduction of multistation seismic data in the period range 50–500 sec for mantle surface waves and 20–100 sec for body waves.
The analysis aims at the reconstruction of the seismic source from the spectrum of its far radiation field and the correlation of its parameters with its depth, size and regional environment.
The capability of the computational procedure has been demonstated in two studies of WWNSS records: one includes a spectral analysis of surface waves from a shallow shock in the Kurile Islands; the other includes a spectral analysis of P waves from 9 shocks in the depth range 550–700 km at Fiji, Mariana, Java, Japan, Peru and Brazil.
Other applications of the proposed data processing routine are foreseen; a tsunami warning system and focal depth determination from spectral modal ratios.
It is believed that a persistent search for stress patterns, based on the processing of a sufficiently large sample of seismic events, is essential to any future program of earthquake prediction.
An analysis of ground motions during the 1957 San Francisco earthquake
Authors: Idriss I. M. , Seed H. Bolton 
Published: July 2021

ABSTRACT
The seismic responses of soil deposits are calculated at four sites where recordings were obtained during the 1957 San Francisco earthquake. The analyses are made utilizing an equivalent linear lumped-mass method of analysis incorporating the soil characteristics at the four sites and estimates of the rock motions at each site based on the record obtained on rock during this earthquake. Comparisons of the maximum amplitudes of ground motions, the time history of ground accelerations, velocity and acceleration spectra and spectral intensities for both computed and recorded ground accelerations indicate a reasonably high degree of agreement. The influence of the amplitude of base rock accelerations on the response of a soil deposit is also discussed and illustrated.
Effect of a fault on explosion-generated ground shock spectra
Authors: Galbraith Frank W. 
Published: July 2021

ABSTRACT
Shock spectrum measurements were made for an underground nuclear explosion at the Nevada Test Site of the U. S. Atomic Energy Commission using 29 reed gages. The objective of the measurements was to determine the effect of a fault zone on shock spectra measured at the ground surface and generated by the explosion. The reed gages were located along two gage lines; one extended to the west and crossed the fault at right angles. The other gage line extended to the north and was generally parallel to the fault. The results showed that the fault zone had an effect on vertical spectra but not on horizontal radial spectra. The vertical gage directly on the fault showed significantly lower displacements for all frequencies above 3 cycles per second but showed no apparent effect on the 3 cps displacement. For gages beyond the fault the vertical spectra for frequencies higher than 3 cps were greater than for corresponding gages along the north gage line. It is believed that this was caused by the upthrust base rock on the side of the fault away from the explosion with a resultant decreased thickness of tuff and alluvium. This resulted in less attenuation of high frequency response than was expected.
Ray theory for an anisotropic inhomogeneous elastic medium
Authors: Vlaar N. J. 
Published: July 2021

ABSTRACT
A ray theory is developed for an inhomogeneous, anisotropic medium, based on the concept of a wave front as the carrier of a discontinuity in particle velocity. The discontinuity conditions of several field quantities involved are formulated and serve to cast the problem in terms of a partial differential equation. The characteristics of this equation subsequently are identified in terms of rays, represented in parametric form as space curves. The energy transport along the rays is formulated by means of transport equations.
The theory is applied in particular to the case of the transversely (horizontally) isotropic, vertically inhomogeneous medium. Equations for rays and travel times are obtained in the form of integrals, which are suited for serving the purpose of numerical computations.
Spectral response to ground displacement at Hattiesburg resulting from nuclear event SALMON
Authors: Blume John A. 
Published: July 2021

Abstract
Spectral response is developed from principal portions of a record of ground displacement in Hattiesburg, Mississippi, resulting from the SALMON event, Project DRIBBLE, an underground nuclear explosion near Baxterville, Mississippi in October 1964. No acceleration records are available for Hattiesburg. As a part of the study it was found that peak response in the important short-period range could be reasonably estimated using as little as one second of selected motion from the entire record, and that a simple stochastic model of this key portion of the ground motion essentially duplicated the peak response.
A magnitude-energy relation for large earthquakes
Authors: King Chi-Yu , Knopoff Leon 
Published: July 2021

Abstract
A relation between the magnitude of a shallow earthquake and the rupture parameters is derived by using a result of dislocation theory and assumptions as suggested from model studies: the average of the pre- and post-shock stresses on a fault and the seismic efficiency are approximately constant. Comparing this relation with observations of the rupture parameters for a number of large shallow earthquakes, the magnitude-energy relation log ⁡ E S = α + 1.7 M is obtained. The value of α is estimated to be approximately 10.
Seismic waves in a quarter plane
Authors: Alterman Z. S. , Rotenberg A. 
Published: July 2021

Abstract
The equations for elastic wave propagation are solved by a finite difference scheme for the case of an elastic quarter plane. A point-source emitting a compressional pulse is located along the diagonal inside the quarter plane. Free-surface conditions are assumed on the boundary lines, so that the problem is nonseparable.
Complete theoretical seismograms for the horizontal and vertical components of displacement are obtained. The effect of different finite difference formulations for the boundary conditions and the effect of different mesh sizes are studied.
Various reflected volume and surface waves are identified, corner-generated surface waves are clearly seen in the seismograms and their particle motion is studied. The amplitude of the pulse observed at the corner is three times the amplitude of the initial pulse.
Steketee's paradox
Authors: Savage J. C. 
Published: July 2021

Abstract
Steketee noted that in a medium subject to invariable stresses at its boundaries, the introduction of a dislocation surface would always increase the strain energy of the medium. This has been misunderstood to imply that the introduction of a dislocation surface in that situation cannot represent rupture since rupture must be an energy-releasing process. It is shown here that the introduction of a dislocation surface can indeed cause a drop in mechanical energy if the entire system is considered. The proof is formulated in terms of internal strain which, of course, is the appropriate formulation of the earthquake problem.
The structure of the Cincinnati arch as determined by short period Rayleigh waves
Authors: Herrmann Robert B. 
Published: July 2021

Abstract
The propagation of Rayleigh waves with periods of 0.4 to 2.0 seconds across the Cincinnati arch is investigated. The region of investigation includes southern Indiana and Ohio and northern Kentucky. The experimental data for all paths are fitted by a three-layer model of varying layer thickness but of fixed velocity in each layer. The resulting inferred structural picture is in good agreement with the known basement trends of the region. The velocities of the best fitting theoretical model agree well with velocity-depth data from a well in southern Indiana.
The moho depth variations under the LASA and their effect on dT/dΔ measurements
Authors: Greenfield Roy J. , Sheppard Robert M. 
Published: July 2021

Abstract
The LASA array in Montana was used to measure the slope of the travel-time curve (dT/dΔ) for events with epicenters to the northwest and southeast. Lateral inhomogeneities under the array introduce large relative arrival time errors (station residuals). A model for the crust under LASA is proposed which can explain the station residuals. This crustal model accounts for the major differences between the measured and Jeffreys-Bullen (J-B) dT/dΔ values. The model was used to correct the measured dT/dΔ profiles for the crustal effect.
Architectural damage to residential structures from seismic disturbances
Authors: Nadolski Michael E. 
Published: July 2021

abstract
Architectural damage to residential structures caused by seismic disturbances was examined to determine meaningful ground-motion damage criteria. Motion records were analyzed to give a response spectrum of building motions. Widely varying amounts of damage resulting from similar peak-particle velocities are explained by the building response envelope which combines the amplitude, duration, and frequency content of the ground motion. A correlation between existing damage and the absolute acceleration values is developed and a comparatively safe amplitude region is shown. A plot of damage complaints versus the pseudo absolute acceleration is presented as an effective damage prediction criterion.
Microearthquake activity following the Parkfield, California earthquake of June, 1966
Authors: Fitch Thomas J. 
Published: July 2021

abstract
A high sensitivity microearthquake recording station was established 10 km from the epicenter of the magnitude 5.5 Parkfield earthquake of June 28, 1966. Beginning 43 hours after the main shock, an hourly average of 22 microaftershocks was recorded for a period of 13 days. Events with magnitudes roughly equivalent to a Richter magnitude of −1.5 were recorded. The amplitude distribution suggests that there was a smaller percentage of small shocks in the Parkfield microaftershock series than has commonly been reported for Japanese and other California aftershock series. b values between 0.8 and 0.9 are commonly reported while the average b value for the Parkfield microaftershock series was 0.59. The distribution of S-P times for the microaftershocks is consistent with the epicentral area defined in other studies as a strip approximately 5 km wide astride a 35 km long trace of the San Andreas fault; however, some evidence suggests that the microaftershock activity extends beyond the zone defined by the larger aftershocks. The spatial distribution of microearthquake activity is shown to be strongly non-uniform within the aftershock zone. The microaftershocks, in general, did not cluster in time about the larger aftershocks (M &gt; 2.0). Of 24 aftershocks with M greater than or equal to 2.0, only one event gave strong evidence of triggering a secondary aftershock series. Assuming that secondary foreshock and/or aftershock series imply the creation or reactivation of a secondary fault, one is led to the conclusion that secondary faulting was a rare occurrence in the Parkfield aftershock zone.
Surface wave components in microseisms
Authors: Der Zoltan A. 
Published: July 2021

abstract
A vertical array of four, three-component sets of seismometers was operated in a well at Grapevine, Texas. Comparison of the amplitude-depth behavior of noise with theoretical Rayleigh and Love wave amplitude-depth curves for the site showed that one has to assume the presence of various Love modes to explain the observations adequately. No such interpretation of the data was attempted for periods below 1 second because at these periods, the multiple coherences are small, which is an indication of the presence of numerous independent surface wave modes in the noise.
Direct measurement of dT/dΔ
Authors: Husebye E. S. 
Published: July 2021

abstract
In this paper we describe and demonstrate a least square method for direct measurement of the wave parameter dT/dΔ. The information necessary for doing this is the coordinates of arbitrarily spaced seismic stations and relative arrival times of the phase under investigation. The dT/dΔ parameter is derived from a function in ϕ and λ, representing the variation of T over the array. An iteration loop is included for examining and selecting a T-response function of simple form, i.e., containing few parameters, and thus making the method applicable even to arrays containing few stations. Using data from Jeffreys-Bullen tables where sometimes random errors are added, the calculated dT/dΔ values at the array centers deviate less than 0.06 from the true value and the estimates have standard errors around ±0.15.
A new analytical method for finding the upper mantle velocity structure from P and S wave travel times of deep earthquakes
Authors: Kaila K. L. 
Published: July 2021

abstract
A new analytical method for the determination of velocity at the hypocenter of a deep earthquake has been developed making use of P- and S-wave travel times. Unlike Gutenberg's method which is graphical in nature, the present method makes use of the least square technique and as such it yields more quantitative estimates of the velocities at depth. The essential features of this method are the determination from the travel times of a deep-focus earthquake the lower and upper limits Δ1 and Δ2 respectively of the epicentral distance between which p = (dT/dΔ) in the neighborhood of inflection point can be considered stationary so that the travel-time curve there can be approximated to a straight line T = pΔ + a. From p = (1/v*) determined from the straight line least-square fit made on the travel-time observation points between Δ1 and Δ2 for various focal depths, upper-mantle velocity structure can be obtained by making use of the well known relation v = v*(r0 − h)/r0, h being the focal depth of the earthquake, r0 the radius of the Earth, v* the apparent velocity at the point of inflection and v the true velocity at that depth.
This method not only gives an accurate estimate of p, at the same time it also yields quite accurate value of a which is a function of focal depth. Calibration curves can be drawn between a and the focal depth h for various regions of the Earth where deep focus earthquakes occur, and these calibration curves can then be used with advantage to determine the focal depths of deep earthquakes in those areas.
A note on the source parameter of the Koynanagar earthquake of 10th December 1967
Authors: Dutta T. K. 
Published: July 2021

abstract
Statistical tests on the first-motion data for the Koynanagar earthquake of 10th December 1967 have been made to select the best values for source parameters out of the six solutions available. It was observed that one of the USCGS determinations that gave the solutions as: epicenter 17°.50 N, 73°.78 E, depth of focus 29 km and origin time 22h 51m 23.7s G.M.T., has the highest degree of accuracy. From records of the earthquake taken at near stations it also seems probable that the actual origin time was less than the value quoted in this solution. The relation between isoseismal distribution and the various solutions are also briefly discussed.
Relative amplitudes ofPandSwaves as a mantle reconnaissance tool
Authors: McGinley John R. , Anderson Don L. 
Published: July 2021

abstractThe unified magnitude, the ratio of the amiplitudes of S to P waves, and travel-time residuals were compiled from published data for the five Seismological Observatories, TFO, UBO, BMO, WMO and CBO. Using one of the stations as a reference, a relative measure of the above quantities was calculated for each of the other stations for each of a number of earthquakes. The stations in the Basin and Range Province are consistent with a markedly higher attentuation of P waves and a high attenuation of S relative to P when compared to the other stations. This latter observation indicates a high Poisson's ratio in the mantle under the Basin and Range. The delay times to these stations are also consistent with the high Poisson's ratio and with a low-velocity upper mantle. The ratio of the amplitudes of long-period S waves to short-period P waves varies by a factor of 4 among these stations.BMO, in eastern Oregon, has a high S/P amplitude ratio compared to other stations and a travel-time residual that is comparable to the observatories in the mid-continent. This may be another example of a seismic “window” into the upper mantle that is generated by underthrusting of the oceanic lithosphere.
A gyroscopic seismometer: Measurements during the borrego earthquake
Authors: Farrell W. E. 
Published: July 2021

abstract
The gyro seismometer, consisting of two counter-rotating pendulous Nordsieck gyroscopes, permits separation of tilts from horizontal motion. Sensitivity is limited by the accuracy with which the gyro orientation can be measured, ∼1 arcsecond rms in a 0.5 Hz bandwidth. This instrumental noise level is equivalent to ground tilts of ∼1 arcsecond and ground velocities of ∼0.1 cm/sec. Peak values in the instrumental pass band (0 to 0.5 Hz) of the tilt and horizontal velocity during the Borrego Mountain, California, earthquake of April 9, 1968, were 1 cm/sec and 10 arcseconds respectively. In La Jolla, 115 km from the epicenter, the static displacement and tilt were less than 1 cm and 0.1 arcsecond (5 × 10−7 radian).
Determination of crustal thickness from spectral behavior of SH waves
Authors: Ibrahim Abou-Bakr K. 
Published: July 2021

abstract
The amplitude spectrum obtained from Haskell's matrix formulation for body waves travelling through a horizontally layered crustal model shows a sequence of minima and maxima. It is known that multiple reflections within the crustal layers produce constructive and destructive interferences, which are shown as maxima and minima in the amplitude spectrum. Analysis of the minima in the amplitude spectra, which correspond to zero phase in the phase spectra, enables us to determine the thickness of the crust, provided the ratio of wave velocity in the crust to velocity under the Moho is known.
Constructing P-velocity models to fit restricted sets of travel-time data
Authors: Backus George , Gilbert Freeman 
Published: July 2021

abstract
A scheme recently proposed by the authors for constructing Earth models which fit a given finite set of gross Earth data is applied to the problem of constructing a P-velocity structure which, within experimental error, fits the observed travel times in the range Δ = 25°(5°)95°. Three such models are obtained, all of which fit the observed travel times with residuals less than 0.06s, whereas 0.5s is the estimated standard error of the observations. The models differ mainly in the outer 700 km of the mantle.