bluuebunny/crossref_metadata_2025_split huggingface dataset:
The use of leaking modes in seismogram interpretation and in studies of crust-mantle structure
Authors: Su Sergio S. , Dorman James 
Published: July 2021

Abstract
Certain normally and inversely dispersed wave trains appearing in the interval between P and S at moderate epicentral distances are identified as specific higher leaking modes. Observed periods of normally dispersed wave trains vary from 7 to 5 sec and from 12 to 9 sec; observed periods of inversely dispersed wave trains increase from about 15 to 35 sec. While the normally dispersed wave trains are generally observed at epicentral distances less than 20°, the inversely dispersed wave trains may be observed at distances up to about 50°. This latter type of wave, with group velocities between 7.0 and 8.5 km/sec, is shown to be controlled by upper mantle structure, and thus represents a possible tool for upper mantle investigations. These waves differ from waves of the Rayleigh and Love modes in that they are more sensitive to the compressional velocity structure than to the shear velocity structure of the waveguide.
PL and shear-coupled PL data which are identified with the fundamental leaking mode were obtained for two paths in South America. Crustal thicknesses for the path between Buenos Aires and Rio determined independently from PL, shear-coupled PL and Rayleigh wave data agree well with one another. An analysis of the method of obtaining phase and group velocity curves consistent with the shear-coupled PL data shows that this method and this type of data together provide a high degree of precision for the determination of phase velocity curves.
In the theoretical treatment, a rapid, approximate method, which is basically Haskell's (1962) method, was used to obtain dispersion curves for the leaking modes. The results of this method are virtually identical to those of Gilbert (1964) and those of Oliver and Major (1960). The main advantage of the present method is that it provides additional information on particle motion and on the relative amplitudes of the predicted arrivals as functions of phase velocity and period.
Total energy and energy spectral density of elastic wave radiation from propagating faults. Part II. A statistical source model
Authors: Haskell N. A. 
Published: July 2021

abstract
Previously derived expressions for the total energy and energy spectral density of elastic waves radiated by a propagating fault are rewritten in terms of a spacio-temporal autocorrelation of the acceleration of relative displacement over the fault plane. This is interpreted in a statistical sense as the average autocorrelation over an ensemble of earthquakes. An explicit form of autocorrelation function is assumed, depending upon two parameters, a correlation length, and a correlation time, and the total energy and energy spectral density are derived in terms of these parameters. By using scaling laws due to Båth and Duda for earthquake volume and radiation efficiency as functions of magnitude, the statistical parameters may also be related to magnitude.
Tectonics of the arctic seismic belt in the light of fault-plane solutions of earthquakes
Authors: Scheidegger A. E. 
Published: July 2021

abstract
A statistical method devised earlier by the writer for the tectonic interpretation of fault plane solutions of earthquakes, is applied to fault plane solutions of Arctic earthquakes which were recently published in Russia. It is shown that the earthquakes on the Greenland side of the Arctic seismic belt represent the same tectonic pattern as seen on the Mid-Atlantic Ridge, whereas the earthquakes on the Siberian side are tectonically connected with the Verkhoyan range.
Instrumental measurement of slippage on the Hayward fault
Authors: Bolt Bruce A. , Marion Walter C. 
Published: July 2021

abstract
A differential transformer has been used as a displacementmeter across a crack in a culvert under the Memorial Stadium, UC Berkeley. The crack is believed to be the result of progressive right-lateral slippage in recent years along the Hayward fault which traverses the stadium. The displacementmeter recorded continuous right-lateral slippage from October 7, 1965 to January 9, 1966. The average rate of movement would amount to about 0.21 inches per year.
Variations in the measured displacement show no significant correlation with the present occurrence of small local earthquakes.
A physical model of the observed fault slippage is outlined, based on the strain-release-by-rupture theory for the origin of shallow earthquakes. The model predicts that strain in the crystalline basement along the fault zone may be accumulating.
Surveys for crustal movement along the Hayward fault
Authors: Pope A. J. , Stearn J. L. , Whitten C. A. 
Published: July 2021

abstract
Several networks of closely spaced points have been established along the Hayward fault for the purpose of monitoring slippage. The results of 1951, 1957 and 1963 surveys of a larger network covering the San Francisco Bay Area are shown graphically. Shear data as calculated from the 1951 and 1957 surveys are tabulated for each triangle of the net. The results obtained from the survey data indicate a larger movement during the 1951–1957 period.
Shallow strain seismograph installation at the Wichita Mountains Seismological Observatory
Authors: Shopland Robert C. 
Published: July 2021

abstract
An experimental shallow strain seismograph was installed at the Wichita Mountains Seismological Observatory in June, 1963. Short-period and long-period pendulums are operated in combination with strain seismometers to study the improvement in the discrimination of wave types and the improvement in signal-to-noise ratio for P waves. Four 20 m horizontal strain seismometers with velocity and displacement transducers are oriented at 45 deg intervals at an average depth of 3.6 m. The least detectable strain increment for Rayleigh waves with the velocity transducer is 4 × 10−13 at 1 Hz with short-period galvanometers, and 1.4 × 10−12 at 100 sec with long-period galvanometers, where Johnson noise is the limiting factor. The least detectable strain increment with the displacement transducer is 2.5 × 10−12 in the range 0.01–10 Hz. A preliminary evaluation of environmental effects indicates that high humidity in the vault requires sealing of the instruments. The vault must be sealed against wind pressure changes. Wind noise from air-to-ground coupling is equal to the amplitude of 0.5-sec microseisms (1.0 mμ peak-to-peak) at a wind velocity of about 14 km/h at a depth of 3.6 m. Seasonal drift rates as high as 30 μ per month, corresponding to a vault temperature change of 5°C, prevent unattended operation of the displacement transducers without drift compensation.
The response of a shear rod to a transient sinusoidal excitation
Authors: Gershanik Simón 
Published: July 2021

abstract
Taking into account that the behavior of a building under the action of ground acceleration may be represented in a first approximation by the behavior of a rod, the latter was investigated by the author in three previous papers. To extend the results obtained previously, the response of an undamped shear rod, fastened at one end and excited by a transient sinusoidal acceleration, has been considered and a closed expression, which may be useful as a reference for more complicated cases, has been obtained. The expression was found following a method similar to D'Alembert's of solving the equation of the vibrating string. Formulae for the case of resonance and for the seismic load are also given.
Effect of undulating bed on “singing”
Authors: Bose S. K. 
Published: July 2021

abstract
The effect of a sinuous undulating bed, on the “singing” phenomenon discovered by Burg, has been investigated. It has been shown that if the amplitude of undulations is small and if their wave length is much greater than those of the different harmonics in “singing”, the first harmonic appears if the amplitude is less than 0.083 times the water depth. In a case when the wavelength of some of the harmonics is much greater than that of the undulations, waves with slightly different wave lengths appear instead of odd harmonics. It is therefore concluded that, in a very gradual undulating bed, not necessarily sinuous, “singing” phenomenon may take place, while in a highly irregular rough bed, it may be totally absent.
Spectral analysis of digitized seismic data
Authors: Huang Y. T. 
Published: July 2021

abstract
Techniques of spectral analysis used for digitized data are discussed in this article from a nonstatistical viewpoint. By a generalization of the theory of linear equations and a truncation of Fourier series, a unique relationship similar to the Fourier Transform Theorem for continuous functions can be derived. Application of this theorem to Fourier series shows how aliasing of frequency occurs. Further application to digitized Fourier transforms indicates loss of aperiodicity in general. Depending upon the choice of fundamental frequencies, we will be able to perform data stacking. Some simple examples shown in the text reveal dependence of phase spectra on different modes of digitization. The phenomenon is associated with analysis of discontinuous functions by a digital method. Only deterministic investigations are conducted in this article.
Noise attenuation in shallow holes
Authors: Douze Eduard J. 
Published: July 2021

abstract
Significant improvements in the performance of short-period seismograph recordings are sometimes obtained in shallow holes (&lt;300 m). Wind noise attenuates rapidly with depth and becomes insignificant at depths of 60 m or less. In the presence of low-velocity weathered layers, the normal background noise decays rapidly with depth and significant improvements in signal-to-noise ratios are obtained. In the absence of a low-velocity zone, only a small attenuation in the background noise level is obtained. Little or no wind noise is converted into traveling seismic waves.
Azimuth and slowness anomalies of seismic waves measured on the central California seismographic array. Part II. Interpretation
Authors: Otsuka Michio 
Published: July 2021

abstract
An interpretation is given here of the azimuth and slowness anomalies for P waves measured on the seven northern stations in the telemetry seismographic array in central California which was described in Part I of this paper. The array provides a new method of investigating the structure of the upper mantle in an important oceanic-to-continental transition region. The structural feature which is primarily responsible for these anomalies is apparently located in the upper mantle within a depth of order 100 km of the surface. Examination shows that if these anomalies are attributed to a thickening crust alone, a dip of the Mohorovičić discontinuity as steep as 20° must be assumed. Further analysis suggests a solution having a moderately dipping Mohorovičić discontinuity below which a second, deeper interface has a velocity decrease downward and a steep dip toward the ocean.
An alternative hypothesis to that of Press and Biehler is formulated which explains traveltime anomalies of certain California stations in terms of a regional structural trend.
The field from an SH-point source in a continuously layered inhomogeneous medium: I. The field in a layer of finite depth
Authors: Vlaar N. J. 
Published: July 2021

abstract
Expressions are derived for the field from an SH point source in a stratified heterogeneous layer of finite depth. It is found, that for a periodic disturbance, the contribution to the far field is mainly due to at most a finite number of unattenuated normal Love modes. The transient response of the medium is obtained by a Fourier synthesis. The final expressions are of a simple form, involving the eigenfunctions of a Sturm-Liouville boundary value problem. The excitation of a certain mode as a function of frequency and source depth is formulated in a concise form.
The earthquake sequence of November 1964 near Corralitos, California
Authors: McEvilly Thomas V. 
Published: July 2021

abstract
A sequence of more than 100 aftershocks with magnitudes as low as −0.1 was recorded following a magnitude 5.0 earthquake on November 16, 1964, in the San Andreas fault zone of central California. The sequence was monitored in detail by three temporary seismographic stations at distances less than 15 km and the surrounding telemetry array. Nearly all of the 35 earthquakes which could be located clustered in a focal region about 4 km in diameter at a depth near 12 km and exhibited uniform first motion radiation patterns. First motion fault plane solutions are consistent with the right lateral transcurrent motion characteristic of the San Andreas fault. Exceptions to this uniform radiation pattern in the concentrated focal region occurred near the times of two large aftershocks apparently on another fault about 5 km away.
Coupled bending and torsional oscillations of a modern skyscraper
Authors: Medearis Kenneth 
Published: July 2021

abstract
The use of electronic digital computers for solving complex engineering problems has instigated significant changes in solution methods. Matrix algebra and numerical analysis techniques are now being utilized extensively in dynamic and static structural analysis. Seismic structural problems which were previously solved using approximate methods, because of the impossibility of “exact” numerical calculations, are now being solved using these techniques in conjunction with computers.
Plresent day building codes advocate “static methods” of seismic structural anaysis where in the engineer is directed to use coefficients for determining design lateral loads. Empirical formulas are given for calculating T, the natural period of vibration of a structure. However, uncertainty exists regarding the empirical calculation of T for unsymmetrical structures subject to coupling between their bending and torsional vibratory motions. Dynamic coupling occurs when the center of mass and the center of rigidity of a structure are not coincident, resulting in motions, under seismic excitation, which may be of prime importance.
The tallest structure in San Francisco, the forty-three story Wells Fargo Building, is subject to such coupling. The theoretical methods of analysis utilized in determining the dynamic characteristics of this uni-directionally symmetric structure are described in this paper. With three possible vibratory motions per story, two translational and one rotational, the resulting problem is seen to be a formidable one involving one hundred twenty-nine degrees of freedom. Using normal mode theory in conjunction with a matrix formulation of the governing coupled differential equations, frequency and vibratory mode solutions are obtained using a digital computer.
Surface waves across the Pacific
Authors: Saito Masanori , Takeuchi Hitoshi 
Published: July 2021

Abstract
Making use of Rayleigh and Love wave dispersion data, Santô divided the Pacific into seven regions. From his map and compiled group velocity dispersion curves, upper mantle structure in the Pacific in which the depths of the low velocity layer and the shear wave velocity are changing systematically from continent to ocean is obtained. In orogenic regions such as Japan and its surroundings, extremely low velocity layer in which the shear wave velocity is about 4.3 km/sec is just under the Moho. In the oceanic side of this region, the layer is overlain by the normal mantle material with shear wave velocity of about 4.6 km/sec and in the pure oceanic region this extremely low velocity layer disappears. The so-called ‘low velocity layer’ which is believed to begin at the depth of about 60 km under the ocean is present in the oceanic region but the shear wave velocity in the layer may be a little higher than that obtained by earlier works.
The field from an SH point source in a continuously layered inhomogeneous half-space
Authors: Vlaar N. J. 
Published: July 2021

Abstract
The propagation of waves due to the presence of an SH point source in the interior of a piecewise continuously stratified half-space is studied. The physical parameters governing the wave propagation, i.e. the rigidity and the density, are assumed to be arbitrary piecewise continuous functions of depth with constant finite limiting values as depth goes to infinity. The analysis is based on spectral theory of boundary value problems associated with ordinary linear second order differential equations. It is found for the time harmonic case that the final field representations are given in the form of a finite residue series, plus a branch line integral, the first representing the normal mode contribution to the field. The field expression appears to have a symmetrical form with respect to field point depth and source depth, involving solutions connected with free wave propagation. This enables one to draw immediately conclusions regarding the influence of the source depth and the frequency on the spectral excitation of the normal modes if numerical knowledge of free Love waves is assumed to be known.
Crustal refraction profile, Oregon coast range
Authors: Berg Joseph W. , Trembly Lynn , Emilia David A. , Hutt Jeremy R. , King John M. , Long Leland Timothy , McKnight William R. , Sarmah Survya K. , Souders Robert , Thiruvathukal John V. , Vossler Donald A. 
Published: July 2021

Abstract
Seven temporary and three permanent seismograph stations recorded seismic waves to a distance of about 270 km from a 110,000 pound quarry blast detonated near Depoe Bay, Oregon. The recording stations were in a north-south line along the northern coast range of Western Oregon and Washington. The travel-time data indicate an apparent shallow crustal thickness (about 16 km) for this region. The time versus distance data were not continuous beyond 130 km from the source which may have resulted from any combination of the following causes: (1) insufficient source energy; (2) lateral geological variations; and/or (3) a subcrustal negative velocity gradient.
On a moving stress discontinuity in a porous, liquid-saturated solid
Authors: Mukhopadhyay Arabinda 
Published: July 2021

Abstract
The stresses produced in a liquid-saturated porous solid by a moving discontinuity of shear stress inside the medium have been considered in this paper. The solutions for the stresses have been obtained in simple closed forms for certain types of moving stress discontinuity. It has been found that the nature of the stresses depends considerably on the velocity of the moving stress discontinuity. If this velocity exceeds a certain value, depending on the nature of the medium, the solutions for the stresses are found to contain delta functions, which are taken to represent discontinuities of stress along certain lines.
Short-period seismic noise
Authors: Douze E. J. 
Published: July 2021

abstract
This report consists of a summary of the studies conducted on the subject of short-period (6.0-0.3 sec period) noise over a period of approximately three years. Information from deep-hole and surface arrays was used in an attempt to determine the types of waves of which the noise is composed. The theoretical behavior of higher-mode Rayleigh waves and of body waves as measured by surface and deep-hole arrays is described. Both surface and body waves are shown to exist in the noise. Surface waves generally predominate at the longer periods (of the period range discussed) while body waves appear at the shorter periods at quiet sites. Not all the data could be interpreted to define the wave types present.
Statistical properties of Rayleigh waves due to scattering by topography
Authors: Hudson J. A. , Knopoff L. 
Published: July 2021

abstract
The two-dimensional problems of the scattering of harmonic body waves and Rayleigh waves by topographic irregularities in the surface of a simplified model of the earth are considered with especial reference to the processes of P-R, SV-R and R-R scattering. The topography is assumed to have certain statistical properties; the scattered surface waves also have describable statistical properties. The results obtained show that the maximum scattered seismic noise is in the range of wavelengths of the order of the lateral dimensions of the topography. The process SV-R is maximized over a broader band of wavelengths than the process P-R and thus the former may be more difficult to remove by selective filtering. An investigation of the process R-R shows that backscattering is much more important than forward scattering and hence topography beyond the array must be taken into account.
Body waves as normal and leaking modes. Part I: Introduction
Authors: De Bremaecker J. Cl. 
Published: July 2021

abstract
Realistic artificial seismograms may be computed by considering body waves as sums of normal or leaking modes of surface waves: the S wave and those arriving after S may be considered as sums of higher normal modes of Rayleigh waves (RiN) and Love waves (LiN); in this case the apparent velocity c &lt; βn. Earlier arrivals are generally due to the first kind of leaking modes of Rayleigh waves (RiL1) for which βn &lt; c &lt; αn. Deep reflections in seismic prospecting are RiL2 for which c &gt; αn. Synthetic seismograms can be computed by double Fourier transformation in those two last cases. Alternately the method of residues followed by a single Fourier (or Laplace) transformation may be used in all cases. Earth-stretching approximations should give excellent results for SH waves and may give satisfactory results for P and SV waves.
Reflection and transmission from a plane layered core-mantle boundary
Authors: Teng Ta-Liang 
Published: July 2021

abstract
A class of transfer functions in terms of layer matrices is derived, giving the transmission and reflection of plane harmonic P or S waves incident from either side of a plane layered core-mantle boundary. A computer program coded in complex arithmetic for the IBM 7094 is used to evaluate these functions. Numerical values obtained from five suggested models of the core-mantle boundary are compared and discussed. The aim is to formulate the method, and to establish some general guide, for the studies of the structure of the core-mantle boundary and the affenuation of seismic waves inside the core.
Master curves for the response of layered systems to compressional seismic waves
Authors: Fernandez Luis M. 
Published: July 2021

abstract
The layers of the earth's crust act as a filter with respect to seimic energy arriving at a given station. Consequently the motion recorded at the surface depends not only on the frequency content of the source and on the response characteristics of the recording instrument, but also on the elastic parameters and thicknesses of the transmitting layers. This latter dependence is the basis for a method of investigating the structure of the crust and upper mantle.
To facilitate this investigation a set of master curves for the transfer functions of the vertical and horizontal component of longitudinal waves and their ratios is presented. The calculation of these curves is in terms of a dimensionless parameter. This calculation allows one to group the curves corresponding to different crustal models into families of curves. The characteristics of these curves are discussed from the point of view of their “periodicity” in the frequency domain and of their amplitude in order to investigate the influence of the layer parameters. Considerations, either of constructive interference or of Fourier analysis of a pulse multiply reflected within the layer system, reveal that the amplitudes of the transfer curves depend on the velocity contrasts at the interfaces of the system. The “periodicity” or spacing of the peaks depends on the time lags between the first arrivals and the arrivals of the different reverberations. Closely spaced fluctuations correspond to large-time lags, and widely spaced fluctuations to short-time lags.