bluuebunny/crossref_metadata_2025_split huggingface dataset:
The azimuthal and polar radiation patterns obtained from a horizontal stress applied at the surface of an elastic half space
Authors: Cherry J. T. 
Published: July 2021

Abstract
The body waves and surface waves radiating from a horizontal stress applied at the free surface of an elastic half space are obtained. The SV wave suffers a phase shift of π at 45 degrees from the vertical. Also, a surface wave that is SH in character but travels with the Rayleigh velocity is shown to exist. This surface wave attenuates as r−3/2. For a value of Poisson's ratio of 0.25 or 0.33, the amplitude of the Rayleigh waves from a horizontal source should be smaller than the amplitude of the Rayleigh waves from a vertical source. The ratio of vertical to horizontal amplitude for the Rayleigh waves from the horizontal source is the same as the corresponding ratio for the vertical source for all values of Poisson's ratio.
Azimuthal asymmetry of a point source in a cylindrical low velocity medium
Authors: Meecham W. C. , DeNoyer John 
Published: July 2021

Abstract
The geometry of the medium in the vicinity of an otherwise symmetrical source is shown to produce a frequency dependent variation of amplitude with azimuth. The model considered is a cylindrical low velocity and low density fluid medium that is contained in a full space of a higher velocity and density fluid material. A simple harmonic point source is located on the axis of the cylinder. Amplitudes in the higher velocity medium at large distances from the source are found to be functions of the velocity ratio and the density ratio of the two media, the radius of the cylinder, the wavelength, and the angle between the axis of the cylinder and a line connecting the point of observation with the source.
Epicentral intensities and damage in the Hebgen Lake, Montana, earthquake of August 17, 1959
Authors: Steinbrugge Karl V. , Cloud William K. 
Published: July 2021

ABSTRACTAn extensive fault scarp system was formed during the Hebgen Lake earthquake of August 17, 1959 (11:37:15 p.m., M.S.T., Gutenberg-Richter magnitude 7.1). Bedrock beneath Hebgen Lake warped, rotated, and caused a seiche in the lake. A major landslide dammed Madison Canyon, causing a lake to form above the slide. An estimated 19 persons were buried by the slide. Other slides and rock falls took out sections of the main highway north of Hebgen Lake and closed many roads in Yellowstone Park.Small unit masonry structures as well as wooden buildings along the major fault scarps usually survived with little damage when subjected only to vibratory forces. The unit masonry buildings, in particular, had little or no earthquake bracing. Intensity at the major scarp has been given a Modified Mercalli Scale rating of X. However, the maximum intensity ratings based on vibratory motion even a few feet away from the scarps were VII or VIII. Within the limits of observation there was little or no reduction in vibratory intensity 5 to 10 miles away compared to that at the fault. This is not to say that the ground motions were similar. At the closest strong-motion seismograph station (Bozeman, 58 miles from the epicenter) maximum recorded acceleration was about 7 per cent gravity. The earthquake was generally felt in about a 600,000 square mile area, mostly north of the instrumental epicenter.The earth-fill Hebgen Dam was within 1000 feet of a major scarp. The dam was significantly damaged, but it continued to be an effective structure.
Crustal structure of the Iceland region from dispersion of surface waves
Authors: Tryggvason Eysteinn 
Published: July 2021

ABSTRACTA number of Icelandic records of earthquakes originating in the Mid-Atlantic Seismic Belt between 52° and 70° N. lat. have been investigated. The surface waves on these records are chiefly in the period interval 3–10 sec, and are first mode Love-waves and Rayleigh-waves. The surface wave dispersion can be explained by a three-layered crustal structure as follows. A surface layer of S-wave velocity about 2.7 km/sec covering the whole region studied, a second layer of S-wave velocity about 3.6 km/sec covering Iceland and extending several hundred kilometers off the coasts and a third layer of S-wave velocity about 4.3 km/sec and P-wave velocity about 7.4 km/sec underlying the whole region. The thickness of the surface layer appears to be about 4 km on the Mid-Atlantic Ridge south of Iceland and in western Iceland, 3 km in central Iceland and 7 km northwest of Iceland. The second layer is apparently of similar thickness than the surface layer, while the third layer is thick; and the surface wave dispersion does not indicate any layer of higher wave velocity. This 7.4-layer is supposed to belong to the mantle, although its wave velocity is significantly lower than usually found in the upper mantle
The mechanism at the focus of an earthquake
Authors: Scholte J. G. J. 
Published: July 2021

abstract
The displacement of a homogeneous medium has been calculated supposing the movement to be generated by a time-harmonic stress on a sphere. This primary stress is defined by the radial pressure on the focal sphere and by two functions describing the variation of the tangential stress along its surface. These functions are developed into series of spherical harmonics and the partial movement corresponding to each term of these series determined. The theory also treats stress systems exerting a moment on the focal region; such systems are not considered in previous investigations.
P and S amplitudes of two earthquakes of the single force couple type
Authors: Ritsema A. R. 
Published: July 2021

abstract
Fault plane solutions of the Alaska earthquake of April 7, 1958 and of the Taiwan earthquake of April 26, 1959 are presented; the solutions are based on the initial motion directions of P and S waves at many stations all over the world. Qualitatively, the data concerning both shocks relate to a focal point-source of a single force couple with moment. The field data of Davis (1960) have been used to determine the position of the fault plane in the Alaska earthquake.
It is shown that the initial motions are not implicitly needed to determine the polarization angle of the S waves, and that if the initial motion is obscured, the maximum amplitudes of S in two horizontal components will suffice.
Incident amplitudes of P and S waves were determined and compared with theoretical amplitudes in the point-source model. For the individual shocks there is a consistent difference between the observed amplitude ratio ub/ua and the theoretical ratio. This is confirmed by a frequency analysis of some of the P and S wavelets. The difference is not the same for the two shocks investigated. It seems likely that the difference is related to the size of the seismic source.
Correction of seismograms for the transfer function of the seismometer
Authors: Bogert Bruce P. 
Published: July 2021

abstract
If digitized seismic data is collected through a seismometer whose transfer function is known, it is not difficult to design a digital filter which will substitute a given band-pass transfer function for that of the seismometer. Various filters of this kind have been applied to digitized records of teleseisms registered on a Benioff short-period vertical seismometer at Chester, New Jersey. After digital filtering on a computer, the resulting data is converted to analog form and recorded on a seismograph drum for visual examination. These records indicate, (1) over the frequency range of interest for teleseismic registration, the seismograph may be regarded as a constant leading phase shift of 270 degrees, a 0.35 second time delay, and a phaseless amplitude function, (2) that it may not be easy to improve on the transfer function of the Benioff instrument for the detection of first motion, and (3) that some additional high-pass filtering might improve the signal-to-microseism ratio at times when the 2-4 second microseism level is high.
S-wave studies of earthquakes of the North Pacific, Part II: Aleutian Islands
Authors: Stauder William , Udias Agustin 
Published: July 2021

Abstract
The polarization of the S wave at stations distributed azimuthally about the source is examined for each of twenty-five Aleutian Island earthquakes. A combination of data from the first motion of P and from the polarization of S is then used to study the focal mechanisms of the earthquakes. This combination of P and S wave data is found to make possible a good determination of the focal mechanism in cases where data from the first motion of P alone do not suffice.
The earthquakes are divided into three groups according to three basic patterns of S wave polarization. The first group (fourteen earthquakes) corresponds to a double couple. The second group (five earthquakes) and the third group (six earthquakes) are conformable to conjugate shears and may therefore be explained by single couple sources of opposite moment, respectively. It is shown that a uniform principal stress system predominates in the region and that the axis of greatest compressive stress is normal to the trend of the island arc.
Free spheroidal vibrations of the earth at very long periods, Part I— Calculation of periods for several earth models
Authors: Alsop Leonard E. 
Published: July 2021

Abstract
Periods of free vibrations of the spheroidal type have been calculated numerically on an IBM 7090 for the fundamental and first two shear modes for periods greater than about two hundred seconds. Calculations were made for four different earth models. Phase and group velocities were also computed and are tabulated herein for the first two shear modes. The behavior of particle motions for different modes is discussed. In particular, particle motions for the two shear modes indicate that they behave in some period ranges like Stoneley waves tied to the core-mantle interface. Calculations have been made also for a model which presumes a solid inner core and will be discussed in Part II. The two computer programs which were made for these calculations are described briefly.
Free spheroidal vibrations of the earth at very long periods, Part II— effect of rigidity of the inner core
Authors: Alsop Leonard E. 
Published: July 2021

Abstract
Numerical calculations have been made on an IBM 7090 of the periods and particle motion with depth of the lowest order free spheroidal vibrations of the fundamental and first two higher modes with inner core shear velocity as a parameter. All calculations were made for a model with velocities according to Jeffreys and with densities obeying Bullen's model B. These calculations show that the effect of the inner core shear velocity on these periods is slight, except for those velocities at which the modes have periods near to the periods of core modes. This means that observations of long period free vibrations will probably not give much information about rigidity of the inner core. A mode of vibration having many of the properties of the mode suggested by Slichter has been discovered. In addition, it appears that the presence of a solid inner core brings into existence many core type modes with periods both shorter and longer than the original core mode predicted by Alterman, Jarosch, and Pekeris.
The Buyin-Zara (Iran) earthquake of September, 1962 a field report
Authors: Ambraseys N. N. 
Published: July 2021

Abstract
The Buyin-Zara earthquake of 1 September 1962 originated on the Ipak fault and it was felt over most of Northern Iran. This newly named fault and its branches run for 64 miles, from Ipak, about W-05°-N, across the mountains south of Buyin, to Takhrijin, 4 miles west of Ab-i-Garm. During the earthquake of September 1, 1962 and its aftershocks, at least 64 miles of surface rupture occurred progressively along this line, and at leas two stages of progressive faulting were involved. Most probably, one from Rudak from where the fracture progressed east to Ipak, and a deeper fracture, with very weak surface evidence from Indrejin progressing east to Tofak.
The earthquake killed 12,225 and injured 2,776 persons. It damaged beyond repair 21,310 houses and killed 35% of the livestock in the area. The maximum intensity of the shock did not exceed IX MM. Small landslides and rock falls occurred on steep slopes and temporary springs were formed.
Velocities of mantle Love and Rayleigh waves over multiple paths
Authors: Toksöz M. Nafi , Ben-Menahem Ari 
Published: July 2021

Abstract
Phase velocities of Love waves from five major earthquakes are measured over six great circle paths in the period range of 50 to 400 seconds. For two of the great circle paths the phase velocities of Rayleigh waves are also obtained. The digitized seismograph traces are Fourier analyzed, and the phase spectra are used in determining the phase velocities. Where the great circle paths are close, the phase velocities over these paths are found to be in very good agreement with each other indicating that the measured velocities are accurate and reliable. Phase velocities of Love waves over paths that lie far from each other are different, and this difference is consistent and much greater than the experimental error. From this it is concluded that there are lateral variations in the structure of the earth's mantle. One interpretation of this variation is that the mantle under the continents is different from that under the oceans, since the path with the highest phase velocities is almost completely oceanic. This interpretation, however, is not unique and variations under the oceans and continents are also possible.
Group velocities are computed from the phase velocities and are also directly measured from the seismograms. The group-velocity curve of Love waves has a plateau between periods of 100 and 300 seconds with a shallow minimum at about 290 seconds. The sources of error in both Fourier analysis and direct time domain methods of phase velocity measurement are discussed.
On uniqueness in dynamic poroelasticity
Authors: Deresiewicz H. , Skalak R. 
Published: July 2021

Abstract
Conditions are derived sufficient for uniqueness of solution of the field equations of Biot's theory of liquid-filled porous media, particular attention being paid to continuity requirements at an interface between two such dissimilar materials. It is found that at an interface two distinct sets of conditions will satisfy the demands of the mathematical uniqueness theorem, one of them being discarded on physical grounds. The permissible set is then discussed in relation to a number of possible models of the structure of a pair of elements in contact. The special cases of an impermeable elastic solid or a liquid medium in contact with a saturated porous solid are also examined.
An eigenvalue method for the statistical evaluation of fault plane solutions of earthquakes
Authors: Fara H. D. , Scheidegger A. E. 
Published: July 2021

Abstract
A method for the calculation of the tectonic motion direction in an area from fault plane solutions of earthquakes is presented. This method is similar to an earlier one described in the literature, but with an improved weighting procedure of the input data. The problem then reduces to that of calculating the eigenvalues and eigenvectors of a certain matrix. The new method enables one for the first time to get easily a value for the scattering of the input data. The method is first applied to a test case, and then to a series of earthquakes that occurred in the vicinity of the Marianas Islands.
Source wave forms of three earthquakes
Authors: Benioff Hugo 
Published: July 2021

Abstract
Strain seismograms of the Montana shallow earthquake of August 17, 1959 recorded at Isabella, California have the wave pattern predicted in 1904 by Lamb for a surface pressure pulse. This is equivalent to a dipole source such as given by the vertical bilateral fault slip which was observed at the surface. Similar recordings made at Ñaña of the deep Peruvian earthquakes of August 19 and 30, 1961, (Δ = 600 ± km, h = 600 ± km) have the pattern calculated by Pekeris for a buried vertical downward force in the form of a step in time. It thus appears that these shocks were generated by a sudden volume contraction at the focus which could be the result of a sudden change of state.
Failure of conventional seismographs to record the patterns calculated by Lamb and by Pekeris is due to their low sensitivity to the very long period ground movement components involved, and their relatively high sensitivity to the short period components which are rendered oscillatory by the departure of the crustal characteristics from the homogeneous half space assumed in the theoretical computations.
Lamb's problem for an inhomogeneous medium with constant velocities of propagation
Authors: Karlsson Thorbjorn , Hook Joseph F. 
Published: July 2021

Abstract
A recently introduced method of separation of the vector wave equation of elasticity for certain types of inhomogeneous, elastic media is employed to study the two-dimensional problem of an inhomogeneous, isotropic, half-space whose elastic parameters and density vary as the square of the depth, leaving the velocities of propagation of P and S waves constant.
The Rayleigh wave dispersion curve for this medium is examined. It is found that the medium yields a single Rayleigh mode with Rayleigh wave phase velocity varying between the shear velocity and the Rayleigh wave velocity of a homogeneous medium of the same Poisson's ratio.
The disturbance generated by an impulsive surface line load is considered. An exact solution to this problem is obtained and numerical results for the displacements are presented and compared to the solutions for the corresponding homogeneous medium. The displacements vary inversely with depth and the relative effects of the inhomogeneity as compared to the homogeneous medium increase with distance from the source. On the surface the amplitude of the Rayleigh wave varies sinusoidally with distance from the source. The displacements at times before and behind the Rayleigh wave have similar, i.e. approximately sinusoidal, variation with distance from the source.
General characteristics of active andean volcanoes and a summary of their activities during recent centuries
Authors: Casertano Lorenzo 
Published: July 2021

ABSTRACT
An oceanic deep lies off the Chilean coast, bordered on the east by a coastal mountain range, a discontinuous central valley, and the high cordillera of the Andes.
The Chilean volcanoes are found on lineaments that in general coincide with, or are sub parallel to, axis of the Andes. In north Chile they lie along en echelon fractures and, in some cases, along transverse fractures. In the south, the alignment of the volcanoes lies west of the axis of the Andes. Where the Central Valley is not well developed, active volcanoes are scarce.
Recent lavas range from basalt in the south to rhyolite in the north. Volcanic activity appears to be decreasing.
Details are given of individual volcanoes, and a list of active Andean volcanoes south of Volcan Misti is presented with a historical account of their activity.
Seismological applications of Laguerre expansions
Authors: Dena W. C. 
Published: July 2021

abstract
If we establish a set of orthogonal functions with resonant and decay characteristics quite similar to those of seismic signals, then a few, or at most a few dozen, terms of the series may match significant phases of seismic events. A few hundred terms of a Fourier series might be required for an equivalent match of these same events. One such set of orthogonal functions are those based on Laguerre polynomials.
This paper describes the Laguerre theory which leads to better Fourier transforms (spectra). Laguerre functions are defined over all time, and their frequency responses are known over all frequencies. Therefore, if the Laguerre series converges quickly, then only a few points in time determine the spectra over the entire frequency range. Conversely, a few points in frequency can determine a transient response over all time.
Seismic applications include the transient calibration of seismometers yielding magnifications and phase responses over all frequencies, the automatic Laguerre analysis of Rayleigh waves by an analog computer, and the use of the Laguerre filter as a correlator to enhance pP phases on seismograms.
Study of Love and Rayleigh waves from earthquakes with fault plane solutions or with known faulting. Part 1. A phase difference method based on a new model of earthquake source
Authors: Aki Keiiti 
Published: July 2021

ABSTRACT
For the purpose of examining the basic assumptions underlying the surface wave method of earthquake mechanism study, we investigated Love and Rayleigh waves from earthquakes with known faulting and/or fault plane solutions obtained from initial motion studies. In order to eliminate the effect of the source time function and finiteness of the fault and to concentrate on the nature of the earthquake force system and its space parameters, we are primarily concerned with the phase differences between Love and Rayleigh waves and their amplitude ratios.
We studied about 30 earthquakes which occurred in the Mediterranean region, California, and Japan. The results are given in Part 2, and the method used is described in the present paper. The theoretical phase and amplitude of Love and Rayleigh waves were computed on the basis of observed faulting or fault plane solution under various hypotheses about the equivalent force system. Then, we obtained from the record, the Fourier phase difference of Love and Rayleigh waves, corrected it for propagation in a layered earth and compared it with the corresponding theoretical value.
In computing the theoretical values, we assumed a homogeneous half space for Rayleigh waves. For Love waves, the layered structure of the earth was taken into account in an approximate way. We have constructed a table of the theoretical values for all possible parameters of fault system and also for various focal depths. A part of the table is given in a concise form in Part 3.
The measurement of the phase difference between Love and Rayleigh waves was made by two methods. One is the stationary phase analysis, first applied to seismograms by Brune, Nafe and Oliver (1960), and the other is a filtering-correlation method. The latter method is appropriate for those records where the waves are less dispersed and noise is a factor.
It was found that the single couple hypothesis fails to explain the observations on surface waves, and must be modified in some way. A modified single couple hypothesis is proposed which appears to explain the observations generally better than the double couple hypothesis as will be shown in Part 2.
Study of Love and Rayleigh waves from earthquakes with fault plane solutions or with known faulting Part 3. Table of source phase differences between Rayleigh and Love waves
Authors: Aki Keiiti 
Published: July 2021

ABSTRACTThe table of source phase differences between Rayleigh and Love waves which was described in Part 1 and used in Part 2 is presented in a concise form for the case of a surface focus.