bluuebunny/crossref_metadata_2025_split huggingface dataset:
Local travel-time curves and their geologic implications for the Pacific Northwest states
Authors: Dehlinger Peter , Chiburis E. F. , Collver M. M. 
Published: July 2021

AbstractTravel-time curves were constructed for the Pacific Northwest states based on recordings of recent local earthquakes. Average velocities of Pn and S waves were found to be 4 per cent lower in the region west of the Cascade Mountains than they are to the east of the Cascades, while velocities of P* and P¯ waves are essentially the same in the two provinces. West of the Cascades the velocities obtained are 7.67 km/sec for Pn, 4.37 for Sn, 6.61 for P*, and 5.48 for P¯. East of the Cascades they are 7.96 km/sec for Pn, 4.56 for Sn, 6.60 for P*, and 5.53 for P¯. Intercept times indicate that the crust (above the Mohorovicic discontinuity) is 5 to 10 km thinner to the west than east of the Cascades. Pn velocities are found to be independent of epicentral distance to distances of 1000 km, implying that the corresponding mantle materials and densities are uniform down to the low-velocity layer in each province. In both provinces Poisson's ratio in the mantle is 0.26. From the travel-time curves and gravity data, it appears that the section above the low-velocity layer east of the Cascades is approximately typical or “normal,” while the corresponding mantle west of the Cascades consists of a different or anomalous material. The likelihood of crystal alignment, temperature anomalies, and normal velocity-density relations in the upper mantle sections are discussed.
Seismicity of the Galápagos Islands and vicinity
Authors: Acharya H. K. 
Published: July 2021

Abstract
A study has been made of seismographically recorded submarine earthquakes between 1935 and 1961 in the region between 10°S and 20°N and 75°W and 110°W. Observational material on travel times was taken from the I.S.S., B.C.I.S. and U.S.C.G.S. catalogues for 191 earthquakes. New hypocentral solutions were found in each case by a uniform method of least-square adjustment. The earthquakes occur in the following belts: (a) the crest of the East Pacific Rise, (b) the Tehuantepec Ridge, (c) the Central American Trench, (d) the trench south of Panama and (e) around the Galápagos Islands. Focal depths and magnitudes of earthquakes are discussed. Escarpments appear to be aseismic.
Correction analysis of Jeffreys-Bullen travel time tables
Authors: Husebye Eystein S. 
Published: July 2021

AbstractBy dividing deviations between observed travel times and those of the Jeffreys-Bullen travel time tables into a station and an epicenter correction, it is possible to calculate corrections to these tables. A significant dependence of station and epicenter corrections upon locality is demonstrated. For the epicenter correction this is especially pronounced in the region of Japan. The correlation between calculated corrections and structures is discussed and the conclusion is that the corrections can be explained by velocity anomalies in the crust and upper part of the mantle. However, systematic errors in the calculated values are possible, especially for the epicenter corrections. No systematic correlation between the observed deviations of P and S waves can be detected, although such a relation should be expected from their respective velocity distributions. An appropriate way to improve the epicenter determinations is proposed, by incorporating the station and epicenter corrections in the solution procedure.
Tsunamis and seismic seiches reported from regions adjacent to the Indian Ocean
Authors: Berninghausen Wm. H. 
Published: July 2021

abstract
References have been made in the past to the absence of tsunamis and seismic seiches in the Indian Ocean. However, a survey of available literature indicates that at least 27 such waves have been reported. Most of these were reported from the coastal regions of the seismically active Indonesian Arc, whereas progressively fewer such waves were reported from the coastal regions adjacent to the Bay of Bengal, Arabian Sea, and the southeastern coast of Africa and the western coast of Australia.
The transfer function for P-waves for a system consisting of a point source in a layered medium
Authors: Fuchs Karl 
Published: July 2021

abstract
This paper investigates in what manner the spectrum of body waves radiating from point sources in a multilayered medium over a homogeneous half-space is different from the spectrum of body waves from the same source in an infinite medium. The effect of the system consisting of a point source in a layered crust on the spectrum of P-waves observed at large distances in the half space is studied. Analytical expressions for the transfer function of this system are derived for three types of point sources: an explosive source, a single couple, and a double couple of arbitrary orientation within the crust.
Preliminary numerical computations for the explosive source at various depths in a realistic model of the earth's crust permit the study of the effect of: a) the angle of incidence into the homogeneous half-space, b) the source depth, c) minor variations of the crustal model. In the case of an explosive source the most influential parameter of the transfer function is the source depth. In shallow explosions the low frequency part of the spectrum of body waves is comparatively rejected.
Reflection and refraction of elastic waves at a corrugated interface
Authors: Asano Shuzo 
Published: July 2021

abstract
The effect of a corrugated interface on wave propagation is considered by using the method that was first applied to acoustical gratings by Rayleigh. The problem is what happens when a plane P wave is incident on a corrugated interface that separates two semi-infinite media. As is well known, there are irregular (scattered) waves as well as regular waves. By assuming both the amplitude and the slope of a corrugated interface to be small, quantities of the order of the square of corrugation amplitude are taken into account. In the case of normal incidence for three models considered, the effect of corrugation on reflection is larger than the effect of corrugation on refraction; the amplitude of the regularly reflected waves decreases, and that of the regularly refracted waves and of the irregular waves increases, as the corrugation amplitude becomes larger. Generally, the larger the velocity contrast, the larger the variation of wave amplitude with the wavelength and the amplitude of corrugation. The S wave component generally becomes larger as the wavelength of corrugation becomes smaller. Boundary waves exist, depending upon the ratio of wavelength of corrugation to that of the incident wave. For a specified interface, it is possible that there is a significant difference in wave amplitude as a function of the elastic constants. In the case of oblique incidence, computation was carried out for angles of incidence smaller than 15° for one model. For these small angles of incidence, almost all results for the case of normal incidence still hold. Furthermore, it can be concluded that the effect of the angle of incidence on reflected S waves is larger than for the other waves and that large differences in the amplitudes of waves at different angles of incidence may be expected for the irregular waves.
Use of a high speed computer for the preliminary determination of earthquake hypocenters
Authors: Engdahl Eric R. , Gunst Robert H. 
Published: July 2021

abstract
At the U. S. Coast and Geodetic Survey, where preliminary earthquake locations must be computed from as many as 30,000 initially unrelated P arrivals and associated phases per month, considerable effort has been devoted toward making this process more fully automatic. A single pass program, COAST, has now been developed for use on the IBM 7030 (STRETCH) computer. This program discriminates compatible time groups from an uncorrelated chronological data file, computes a first approximation to the hypocenter using only five stations, and determines the refined hypocenter and earthquake magnitude using all relevant data without any intervention by a seismologist.
Transmission of Rayleigh waves at a corner
Authors: Mal A. K. , Knopoff L. 
Published: July 2021

abstract
Using a Green's function method of approximation, transmission and reflection coefficients are computed for the problem of Rayleigh waves normally incident upon the corner of a homogeneous elastic wedge formed by two stress-free planes. The Rayleigh waves are incident from infinity and travel along one surface of the wedge. The transmitted waves on the second surface and the reflected waves on the first surface are calculated by the application of Huygens' principle. A pair of coupled integral equations for the displacements are obtained by means of a representation theorem. Neglecting the diffracted body waves near the corner, the coupled integral equations are reduced to a pair of algebraic equations. A new feature of the calculation involves consideration of diffracted surface waves travelling toward the vertex. Numberical values of the phase shifts and attenuation factors in the transmitted and reflected waves are computed as functions of the wedge angle. Comparison with experimental results show considerably better agreement than has been obtained previously.
Reflection of elastic waves from a linear transition layer
Authors: Gupta Ravindra N. 
Published: July 2021

abstract
A separation of P- and S-wave potentials is achieved for an inhomogeneous medium in which density is constant and Lame's parameters, λ and μ, are assumed to vary as λ/λ1 = μ/μ1 = (1 + bz)2 where λ1, μ1 and b are constants. The resulting equations are solved for an arbitrary angle of incidence. Plane wave reflection coefficients are obtained for the situation when the material mentioned above forms a transition layer between two homogeneous, elastic half-spaces. First and/or second-order discontinuities in material properties are permitted at the boundaries of the transition layer. Some numerical results are given.
Response of a vertical strain seismometer to body waves
Authors: Gupta Indra N. 
Published: July 2021

abstract
Expressions have been derived for vertical strain due to P and SV type waves arriving at an arbitrary angle of incidence within a semi-infinite medium. The amplitude and phase relationships between vertical strain and vertical displacement have been investigated for both wave types, assuming a Poisson's ratio of 0.25. The effect of finite depth and finite length of the vertical strain instrument has been examined and found to be significant especially for small angles of incidence.
Wind-induced vibrations and building modes
Authors: Ward H. S. , Crawford R. 
Published: July 2021

abstract
This paper outlines the methods that have been used to determine the frequencies and modes of vibration of multistory buildings from their wind-induced vibrations. Three buildings of ten, thirty-eight and forty-seven stories were investigated. A simple theoretical model was used to calculate the frequencies of vibration of the buildings; the model was based on the assumption that there was no joint rotation in the building frames. A comparison of the theoretical and measured values of the frequencies showed that this simple model was a realistic representation of only the smaller building. It is concluded that a model that includes joint rotation would be more realistic for the taller buildings. Auto-correlation and power spectrum analysis of the vibration records were used to obtain an estimate of the damping characteristics of the buildings. The values obtained were 1 to 3 per cent of the critical amount of damping.
Teleseismic response of a uniform dipping crust (part I of a series on crustal equalization of seismic arrays)
Authors: Kane Julius 
Published: July 2021

abstract
Most seismic theory is confined to a consideration of crustal structures that can be abstracted as plane parallel elastic layers. For such configurations, the response of each element of a seismic array will be similar to any other except for a time delay. Signal enhancement of an array located on such an idealized structure can be accomplished by suitable time delays of the individual traces followed by superposition.
On the other hand, if the crustal structure is anything but a plane parallel configuration, the signals received by the individual elements will not be identical to one another, but will include distortion effects characteristic of the local geometry. As a result, the records of seismic arrays located on realistic crustal configurations will have to be equalized to some standard reference if optimum signal processing is to be achieved.
In this paper we introduce a ray procedure for the calculation of theoretical seismograms for the teleseismic response of an array of stations located above a uniform dipping crust (wedge-shaped). In terms of this mathematical model, we demonstrate the signal distortion effects of the geometry and discuss equalization techniques that will permit a superior recovery of the desired signal.
Parkfield earthquakes of June 27-29, 1966, Monterey and San Luis Obispo Counties, California—Preliminary report
Authors: Oakeshott Gordon B. , Allen Clarence R. , Smith Stewart W. , Pakiser L. C. , McEvilly T. V. , Cloud William K. , Steinbrugge Karl V. 
Published: July 2021

abstract
Two earthquakes, M = 5.3 and 5.5, shook the Parkfield area in southern Monterey County, California, at 0409:56.5 and 0426:13.8 GMT, 28 June 1966. They were preceded by foreshocks on the same day at 0100 and 0115. A third shock, M = 5.0, occurred in the same area at 1953:26.2 on 29 June. The earthquakes were followed by a heavy sequence of aftershocks with epicenters along the San Andreas fault zone extending for about 15 miles southward beyond Cholame in San Luis Obispo County. A P-wave first-motion fault plane solution shows strike of vertical fault plane is N 33°W, coinciding with a surface zone of en echelon fault fractures in the pattern characteristic of right-lateral, strike-slip movement. The motion appears to have an upward component on the west side, at about 20° from pure strike slip. Extensive instrumentation within a few miles of the epicentral district gave unusually complete records from foreshock to aftershock sequence. A strong-motion instrument in the fault zone near Cholame recorded the unusually high horizontal acceleration of 0.5 g.
The epicentral region of the earthquakes is on a known active segment of the San Andreas fault. Earthquakes in 1901, 1922, and 1934 in this region were also accompanied by surface faulting. On the published State geologic map, scale 1:250,000, the San Andreas fault zone shows a braided pattern of several branching en echelon major faults. Topographic forms, typical of the features of rift valleys, testify to the recency of fault movements. Small right-lateral surficial displacements had been recognized prior to the late June earthquakes in at least three places on the Parkfield-Cholame trace of the fault. Similar creep, or slippage, has continued since the earthquakes. Extensive nets of survey markers installed by 30 June across the active fault trace had recorded slippage as great as 0.1 inch per day by 12 July. The fault trace associated with the earthquakes is principally in alluvium of unknown depth in Cholame Valley, apparently a faulted graben within the San Andreas fault zone. Under a blanket of Tertiary and Quaternary sedimentary rocks in this part of the southern Coast Ranges, the great fault separates Jurassic-Cretaceous granitic and metamorphic rocks in the western block from Late Jurassic eugeosynclinal sedimentary and volcanic rocks of the Franciscan Formation in the eastern block.
In spite of the large horizontal acceleration recorded near the fault, very little building damage occurred in this sparsely populated region. Small concrete and steel bridges in, and adjacent to the fault trace, did not have their structural strength impaired.
Higher modes of seismic surface waves: Propagation in Eurasia
Authors: Crampin Stuart 
Published: July 2021

Abstract
Second Love and second Rayleigh modes are found to propagate in Eurasia across many different structures; the continent is divided into regions where these higher modes have the same dispersion characteristics. The condition for constructive interference breaks down only when the second modes cross areas of rapid change at oceanic-continental boundaries and under some mountain ranges. There are many paths in Eurasia where the second Love and Rayleigh modes have the same dispersion, and along these paths the two wave trains have a constant phase relationship, suggesting that the modes have some form of elastic linkage.
The S-wave project for focal mechanism studies, earthquakes of 1963
Authors: Stauder William , Bollinger G. A. 
Published: July 2021

Abstract
P- and S-wave data for thirty-five earthquakes selected from among the larger earthquakes of 1963 have been investigated. Focal mechanism determinations for twenty-six of these shocks are here presented. The solutions are based upon a combination of a graphical and a computer method for determining the poles of the nodal planes. In all cases it has been found that the mechanism may be adequately represented by a double couple as an equivalent point source of the focus, although in some few instances a single couple cannot be excluded as a possible alternate interpretation. The solution of a mid-Atlantic earthquake of November 17, 1963 is presented as an example of a focus which clearly conforms to the double couple model.
Special attention is called to the solutions for a series of earthquakes in the Kurile Islands, and to three earthquakes of the mid-Atlantic.
Signal-generated noise recorded at the Eskdalemuir seismometer array station
Authors: Key F. A. 
Published: July 2021

abstract
An investigation of the signal-generated noise at the UKAEA seismometer array station at Eskdalemuir, Scotland, has shown a close correlation between apparent noise sources and topographic features. A particularly strong local source, in the region of a deep river valley, was found and has been studied in some detail.
A wide range seismogram digitizer
Authors: Wickens A. J. , Kollar F. 
Published: July 2021

abstract
A visual seismogram drum-digitizer has been developed with precision adequate for the seismograms generated in standard networks. The variable speed, sampling interval and optical magnification permit convenient and efficient digital conversion of a wide range of record traces for different seismological research purposes.
An analysis of the precision has been made: over a dynamic range of 150 mm errors are less than 50 μ, and time intervals accurate to ±.05 sec for short-period seismograms or ±0.2 sec for long-period records.
The earthquake sequence of September, 1965 near Antioch, California
Authors: McEvilly T. V. , Casaday K. B. 
Published: July 2021

abstract
A foreshock-aftershock sequence associated with an earthquake of magnitude 4.9 on September 10, 1965, in the San Francisco Bay Region is analyzed. The sequence was monitored by nearby Berkeley network stations and by one temporary station in the epicentral region. Precise hypocenters were determined for 29 of the shocks and these clustered in a small focal region with dimensions on the order of a few kilometers and at an average depth of 12 km. Within this focal region a N-S trend was observed with shocks apparently migrating down and then back up the trend.
(First motion radiation patterns were uniform throughout the sequence, and a P-wave fault plane solution for the main shock yielded as one possible source, consistent with observed S-wave polarization, a N-S trending fault with right-lateral motion. The log cumulative frequency of shocks versus magnitude plot yields a slope of b = −0.78. The similarities between this sequence and the 1964 Corralitos sequence are discussed and are shown to be at variance with the 1963 Salinas-Watsonville sequence and, from preliminary indications, from the 1966 Parkfield sequence. As a result, two characteristically different types of earthquake sequences in the magnitude 5.0-5.5 range are defined for the Central California region.
Crustal structure of the Mediterranean sea by surface waves. Part I: Group velocity
Authors: Payo Gonzalo 
Published: July 2021

abstract
The purpose of this paper is to obtain an approximation to the crust-mantle structure of the Mediterranean Region, using only group-velocity data.
Earthquakes whose seismic paths cross totally or partially the Mediterranean Sea have been used. Forty-eight earthquakes have been selected and their corresponding Rayleigh and Love group-velocity dispersion curves were calculated. Most of the records belong to the standard seismological stations installed in the borders of the Mediterranean Sea.
The Rayleigh and Love wave dispersion curves obtained have been classified in five different groups which show the same dispersive character. There is a correlation of such classification with the oceanic percentage and geographic region crossed by the paths, i.e., with the corresponding type of crustal structure.
Crust-mantle theoretical models have been computed for both Rayleigh and Love waves. The dispersion curves of these models fit acceptably into an average of the data of each group. They show a remarkable difference between the eastern and western Mediterranean crust, which is considered as one of the main results of this investigation. The crust to the south of the Ionian and Aegean Seas shows somewhat smaller velocities and larger thicknesses, for the uppermost crustal layers, than that of the western Mediterranean, which seems to be of a more oceanic character.
Attenuation of earthquake generated P waves along the western flank of the Andes
Authors: Sumner Roger D. 
Published: July 2021

abstract
The attenuation of longitudinal body waves generated by local shocks in southern Peru was investigated. Thirty-four shocks, with focal depths between 20 and 180 km, were used in the study of attenuation as a function of depth and as a function of frequency (1-30 cps). Shocks were recorded on magnetic tape at three stations along the western flank of the Andes. The dimensionless specific attenuation factor Q was computed from measurements of the relative change in shape of P-particle velocity spectra with distance from the source. Near surface effects on amplitudes were taken into account. It was found that: Qp(1.5-15 cps) &gt; 1 × 103; the attenuation of P waves increases markedly above 15 cps, probably due to scattering losses; and although absolute Qp values as a function of depth could not be resolved, an increase in P wave attenuation at a depth of about 80 km is suggested. Vp/Vs, determined from S-P and P readings at seven stations for 150 shocks, is significantly higher for oceanic shocks than inland shocks.
Near-surface dispersion studies at Tonto Forest Seismological Observatory
Authors: Linville A. Frank , Laster Stanley J. 
Published: July 2021

abstract
Four local seismic events digitally recorded on a crossed-linear array have been analyzed to evaluate the representation of wave propagation in inhomogeneous earth models in terms of “local” dispersion. The analysis techniques studied are based primarily on the correlation properties of the signals at various receivers. Frequency-wave-number spectra are computed for the events by various methods, and a comparison of the results indicates that the best method is a combination using averaged correlations computed from prewhitened data. The utility of computing dispersion curves from an estimation of the “transfer function” has been evaluated. The studies show the necessity of recording data directly “inline” in areas of rough topography between source and array if “local” dispersion is to be measured. Multichannel prediction studies indicate that the signals are highly nonstationary in space.