bluuebunny/crossref_metadata_2025_split huggingface dataset:
The “little variable factor” a statistical discussion of the reading of seismograms
Authors: Freedman Helen W. 
Published: July 2021

abstract
A number of independent readings of “typical” seismographic records are made, primarily in order to estimate the errors involved in determining the onset of a P wave. The degree of consistency with which a disturbance is called “the first arrival from an earthquake” is discussed. The distribution of reading errors is estimated and a method suggested for improving the accuracy of routine reading of seismograms. This model provides estimates for reading errors of several types of onsets. Finally the classification of onsets into “i” and “e” is shown to be inadequately defined.
Spectral analysis of tsunami records from stations in the Hawaiian Islands
Authors: Loomis Harold G. 
Published: July 2021

abstract
Power spectra for the tsunamis of 13 October 1963, 20 October 1963, and 28 March 1964, as recorded at several stations in the Hawaiian Islands and at Midway, were obtained by digital methods. It was found that a given tsunami produced spectra at nearby stations which were somewhat similar for low frequencies (i.e., out to 1.6 c/ks), but that even this similarity disappeared between spectra from stations as far apart as Hilo and Honolulu (210 miles). Likewise, a given station gives its spectral imprint to tsunamis incident upon it, but only qualitative similarities are found. The time changes in spectra of a tsunami at a given station do not support any simple picture of a local response function. The energy decay curves show the arrival of reflected energy from (sometimes) identifiable sources. The time changes in the mean frequency of incident energy are not immediately explainable.
Analysis of surface-foci travel times
Authors: Carder D. S. , Gordon D. W. , Jordan J. N. 
Published: July 2021

abstract
Regional and teleseismic P wave travel times from surface foci entail relatively fast crustal and upper mantle velocities beneath continental shields, and, in contrast, slow velocities beneath cordillera.
On the average, teleseismic readings from continental and oceanic sources give arrival times 2 sec earlier than the Jeffreys-Bullen zero depth curve. In addition to this overall offset an empirical surface focus curve shows prominent departures from the J-B predictions in the neighborhood of 30° and 60°, where the observations are approximately 2 1/2 to 3 sec earlier than the J-B curve.
As defined in this paper the term “transition zone” refers to the range from 12° to 18° (circa) where the first apparent arrival depends on signal-to-noise conditions. Given sufficient signal strength Pr, an emergent phase which fits a slope of 8.6 to 8.8 km/sec on travel time plots, arrives first. Amplitudes associated with the Pt (P-teleseismic) phase dominate the longitudinal portion of recordings from the transition zone and, if noise levels are high, the observer often interprets Pt as the first arrival.
A mobile seismograph array
Authors: Lehner Francis E. , Press Frank 
Published: July 2021

abstract
A movable array composed of Ranger type seismometers, 60-day film recorders and 7-day magnetic tape recorders housed in compact trailers, has been developed. The array is useful for research requiring frequent instrument relocation such as P-delay, micro-seismicity, aftershock and signal-to-noise ratio studies.
The array unit combines the functions found in conventional fixed stations with a high degree of mobility. Conveniences such as solid state amplifiers, radio and clock circuitry, internal calibration, and minimum installation time are special features.
With the battery supply provided, a one week period of unattended film and tape recording is possible. With commercial power, the instruments can operate unattended for up to sixty days.
Useful magnification up to several million is available, depending on the frequency band selected.
Microearthquake activity recorded by portable seismographs of high sensitivity
Authors: Oliver Jack , Ryall Alan , Brune James N. , Slemmons David B. 
Published: July 2021

abstract
The increase in frequency of occurrence of earthquakes with decreasing magnitude is well known. In a few cases observations have shown that this relation holds for extremely small events, including those with magnitudes well below zero, and that the energy of the smaller shocks is confined largely to the higher seismic frequencies. These facts suggest that portable seismographs with ultra-high sensitivity might record a sufficient number of nearby microearthquakes in a short interval of time, say one day, so that some measure of the seismic activity of a very local area might be obtained very quickly.
This idea was tested in west central Nevada where ten sites were occupied for short intervals of time. Microearthquakes were recorded at rates ranging from several per day to over two hundred per day. Generally, consistently high microseismicity was observed in areas of recent faulting. A lower level of activity, well above that of aseismic areas however, was observed at other sites in Nevada.
Some indication of variation of microearthquake activity with time was obtained. Activity averaged over an interval of about ten hours usually differed by less than a factor of two from the overall mean for that site. In one case, however, swarms of events persisting for a total interval of a little more than one day were observed.
The method appears very promising as a technique for monitoring current tectonic activity.
The application of rational approximations to the solution of problems in theoretical seismology
Authors: Longman I. M. 
Published: July 2021

Abstract
The method of approximate Laplace transform inversion, by analytically inverting suitable rational approximations to a function f¯(p) of the operator p is applied to the problem of propagation from a quadratic pulse point source in a uniform liquid sphere.
Apart from this main problem, the relation between the efficiency of the method and the sharpness of the pulse is illustrated in a general way by considering three simple examples (in descending order of sharpness), namely the approximate inversion of the Laplace transforms of a delayed Heaviside unit function, a simple function having a gradient discontinuity, and a quadratic pulse.
In order to suggest how the technique can be extended to more difficult theoretical seismic problems, the method is applied to a simple function f¯(p) having branch points on the imaginary axis in the p-plane.
A survey of complaints of seismic-related damage to surface structures following the Salmon underground nuclear detonation
Authors: Power Dean V. 
Published: July 2021

Abstract
Following Salmon, the undergound nuclear experiment in Mississippi, numerous unexpected complaints of damage were received from residents living 15 to 40 km away. The claimed damage is mostly cracks in plaster, stucco, and masonry. Ground motion at these ranges was within the predicted safe limits, with peak surface-particle velocities roughly an order of magnitude below the 5 to 10 cm/sec previously accepted as the threshold for damage. It is shown that a 5 cm/sec damage threshold is not descriptive of this area, and revised damage criteria need to be formulated that take into consideration geology, frequency spectrum, and other factors in addition to surface particle velocity. The claimed damage is similar to that normally found in Mississippi homes where it is attributed to poor foundation soils. The triggering by Salmon of naturally occurring settlement cracks is suspected, but the physics of the process is not yet fully understood. Further complications in the survey are introduced by local sociology and psychology and public relations factors.
Estimating the accuracy of source “parameters”
Authors: Freedman Helen W. 
Published: July 2021

abstract
This paper suggests a method for estimating the errors accompanying estimates of seismic source parameters. While the method is a general one, the data here are from 1962 and 1963 and special attention is given to a few regions, such as the Kuriles. The overall standard error of about one-half a degree in each coordinate and four seconds in origin time are broken down and analyzed in terms of magnitude, depth, and location in space and time. The most accurately located earthquakes appear to be those of intermediate depth and magnitude in highly seismic areas. There is some indication that these errors are decreasing with time.
Correction of atmospheric errors in electronic measurements of earth crust movements
Authors: Thompson M. C. , Janes H. B. 
Published: July 2021

abstract
Three methods are described for correcting electronic measurements of earth movement for atmospheric refraction effects. The effectiveness of two of these is discussed in terms of experimental studies using microwave systems. Precision of the order of 1 part in 109 (1 micron in 1 km) appears to be attainable.
Body wave radiation patterns from elementary sources within a half space
Authors: Gupta I. N. 
Published: July 2021

abstract
The known expressions for the polar radiation patterns due to a horizontal or a vertical force, applied at a point within a uniform half space, are used to obtain the body wave radiation patterns from several other elementary seismic sources. Polar radiation patterns from seven elementary line sources, i.e., horizontal and vertical double forces without moment, horizontal and vertical single couples, center of dilatation, center of ratation, and double couple without moment, are first derived. Similar point sources in the three-dimensional space are also considered and the corresponding polar as well as azimuthal radiation patterns are obtained for P, SV, and SH waves. The results obtained include the effect of finite depth of the source below the free surface. Some of the results of Burridge et al for double-couple type seismic sources near a free surface are reproduced in a simple manner.
For the elementary point sources considered here, the azimuthal radiation patterns for a uniform half-space are found to be identical with those for an infinite homogeneous medium. However the polar radiation patterns appear to be profoundly affected by the proximity of the free surface.
Reservoir-dam interaction during earthquakes
Authors: Chopra Anil K. 
Published: July 2021

abstractMost work, to date, on analysis of effects of earthquakes on dams treats dam and reservoir as two uncoupled systems. The importance of interaction between the two systems in determining the water pressure on dams during earthquakes is investigated herein. The analysis presented is approximate in nature and is aimed at exploring the problem. The earthquake acceleration is first modeled as a stationary gaussian white noise process. For this excitation, certain qualitative conclusions concerning importance of interaction effects are derived. Hydrodynamic responses of typical systems subjected to El Centro (1940) earthquake are then determined to confirm these conclusions. On basis of these results, it appears that the interaction between reservoir and dam has significant influence on the hydrodynamic responses during earthquake excitations.
Estimating earthquake magnitude
Authors: Freedman Helen W. 
Published: July 2021

abstract
The disturbingly large variation in magnitude estimates observable in any earthquake catalogue has led to this analysis of one particular catalogue and definition of magnitude. The method employed by the United States Coast and Geodetic Survey is analyzed in the light of theoretical considerations concerning the probability distribution of the variables involved. In particular, the truncation procedure seems to lead to estimates which consistently underestimate the magnitude for large earthquakes, and perhaps overestimate the magnitude for small ones. An alternative method is suggested which leads to estimates which are in good agreement with those provided by Berkeley, Pasadena and Lamont.
The earthquakes of 1965-66 in the Peloponnesus, Greece; a field report
Authors: Ambraseys N. N. 
Published: July 2021

abstractBetween March 1965 and September 1966, two strong earthquakes occurred in central Peloponnesus (Greece). The first shock was connected with the west wall of the Megalopolis depression and it was followed by another shock connected with the opposite wall. The cumulative effects of these two earthquakes, and of two other deeper shocks that occurred further north, were considerable and difficult to separate. Landslides and slumping of the ground accounted for the majority of the damage which increased progressively with the shocks that followed. Submarine and coastal slumping caused additional damage and a small sea-wave was set off in the Gulf of Corinth. At the epicentral area the ground movements were severe, with a double amplitude on the record-plate of a standard Wilmot seismoscope reaching 60 millimeters.
A comparison of free oscillations of oceanic and continental earth models
Authors: Derr John S. 
Published: July 2021

Abstract
It is well-known that Rayleigh and Love waves over continental and oceanic structures have different periods (T) for a given order (n). In the present study, this difference is explored over the spectrum for periods greater than 30 sec, and particularly the graver fundamental spheroidal and torsional oscillations. The oceanic model is the same as the continental model below 400 km depth, is adjusted between 400 km and 10 km to preserve the Earth's overall mass and moment of inertia, and has 5 km of crust and 5 km of ocean. For torsional oscillations, the difference in period for a given n is about 3 sec throughout the range of 2 ≦ n ≦ 120, or 0.15 per cent to 3.3 per cent. However, the two curves for the group velocity are not parallel in this range: continental group velocity increases monotonically with T, while oceanic group velocity has a broad minimum for 160 &lt; T &lt; 200 sec. For spheroidal oscillations, the difference in period for a given n is about 2 sec for 2 ≦ n ≦ 120, or 0.1 per cent to 2 per cent. For n = 0, the difference is only 0.1 sec or 0.008 per cent. The two group velocity curves are almost parallel with minima in the same range, 205 to 210 sec. Comparison with the precision of available measurements of the free periods shows that the presence of an oceanic crust and upper mantle is important for fitting models of the earth to any set of free oscillation observations.
A note on the focal mechanism of the Parkfield, California earthquake of June 28, 1966
Authors: Algermissen S. T. , Harding Samuel T. 
Published: July 2021

Abstract
S-wave polarization studies of the Parkfield, California earthquake of June 28, 1966, indicate that a type II or double couple focal mechanism best fits the available data. The direction of greatest stress derived from the S-wave solution is in general agreement with results derived from geological evidence.
An analysis of seismoscope data from the Parkfield earthquake of June 27, 1966
Authors: Hudson D. E. , Cloud W. K. 
Published: July 2021

AbstractAn analysis of 16 seismoscope records from the Parkfield earthquake indicates the general usefulness of seismoscope data as a supplement to information produced by recording accelerographs. The pattern of attenuation of response spectrum values with distance from the fault was obtained, and certain anomalies in response spectrum values which may be related to local geologic structure were noted. The initial strong ground motions in the immediate vicinity of the fault were found to be predominately transverse to the fault. A direct comparison of seismoscope results with response spectrum curves calculated from recorded groud acceleration-time curves indicates an overall seismoscope accuracy under typical field conditions of 10-15 per cent.
The Parkfield, California, earthquakes of 1966
Authors: McEvilly T. V. , Bakun W. H. , Casaday K. B. 
Published: July 2021

Abstract
The characteristics of the Parkfield, California earthquake sequence of 1966 are presented. Historically, the epicentral region is one of the three most seismic areas along the San Andreas fault in central California. It is characterized, however, by a relatively high incidence of large earthquakes in proportion to smaller shocks, compared to other active zones. The 1966 sequence occurred in an area where measured deformation across the fault for 1959-1965 shows a decrease from about 2 cm/year to the north to zero to the south of the area. Neither micro-earthquake nor normal seismic activity prior to the sequence gave indication of its coming. Seismicity before the sequence was confined to the north of the active zone, with some indication of convergence of foci toward the location of the initial shocks. The early aftershock distribution extended 20 km south of the main shock; cracking occurred to 33 km south of the main shock; and intense aftershock activity for the entire sequence extended 27 km south of the main shock. At least 95 per cent of the earthquakes, including the three largest, have P-wave radiation patterns consistent with right lateral transcurrent motion on the San Andreas fault. Earthquakes of the sequence fall very closely along the fault trace. About 75 per cent of the total strain release for the sequence can be accounted for by earthquakes in the main shock region, the principal shock (M = 5.5) contributing only 25 per cent of the total. The sequence is characterized by a high incidence of large aftershocks, an extensive area of aftershock activity, and average focal depths near 5 km-three properties apparently related, and distinguishing two types of sequence traits in central California.
Deconvolution techniques for linear systems
Authors: Ko Hon-Yim , Scott Ronald F. 
Published: July 2021

Abstract
Superposition for linear systems is the process in which the input is convolved with the transfer function of the system, whereby the output is obtained. Deconvolution is, therefore, the reverse process in which an unknown input (or the transfer function) is calculated from the measured output and a known transfer function (or input). Several methods of deconvolution are developed and the advantages and disadvantages of each are discussed. Examples are given to demonstrate the applicability of the methods.
The Varto Üstükran (Anatolia) earthquake of 19 August 1966 summary of a field report
Authors: Ambraseys N. N. , Zátopek A. 
Published: July 2021

abstract
The Varto-Üstükran earthquake of August 19, 1966, occurred near the east end of the Anatolian fault system in Turkey, very near where an earlier, less intense earthquake had caused damage in 1946. The earthquake had a magnitude 6.8 and it was felt over an area of over 300,000 square kilometers. The epicentral intensity did not exceed IX (MM) and there were signs of faulting over a length of about 30 kilometers. The earthquake killed some 2,500 and wounded 1,300 people. Over 19,000 houses of poor construction were destroyed and 100,000 people were made homeless.
Travel times, apparent velocities and amplitudes of body waves
Authors: Julian Bruce R. , Anderson Don L. 
Published: July 2021

abstract
Surface wave studies have shown that the transition region of the upper mantle, Bullen's Region C, is not spread uniformly over some 600 km but contains two relatively thin zones in which the velocity gradient is extremely high. In addition to these transition regions which start at depths near 350 and 650 km, there is another region of high velocity gradient which terminates the lowvelocity zone near 160 km. Theoretical body wave travel time and amplitude calculations for the surface wave model CIT11GB predict two prominent regions of triplication in the travel-time curves between about 15° and 40° for both P and S waves, with large amplitude later arrivals. These large later arivals provide an explanation for the scatter of travel time data in this region, as well as the varied interpretations of the “20° discontinuity.”
Travel times, apparent velocities and amplitudes of P waves are calculated for the Earth models of Gutenberg, Lehmann, Jeffreys and Lukk and Nersesov. These quantities are calculated for both P and S waves for model CIT11GB. Although the first arrival travel times are similar for all the models except that of Lukk and Nersesov, the times of the later arrivals differ greatly. The neglect of later arrivals is one reason for the discrepancies among the body wave models and between the surface wave and body wave models.
The amplitude calculations take into account both geometric spreading and anelasticity. Geometric spreading produces large variations in the amplitude with distance, and is an extremely sensitive function of the model parameters, providing a potentially powerful tool for studying details of the Earth's structure. The effect of attenuation on the amplitudes varies much less with distance than does the geometric spreading effect. Its main effect is to reduce the amplitude at higher frequencies, particularly for S waves, which may accunt for their observed low frequency character.
Data along a profile to the northeast of the Nevada Test Site clearly show a later branch similar to the one predicted for model CIT11GB, beginning at about 12° with very large amplitudes and becoming a first arrival at about 18°. Strong later arrivals occur in the entire distance range of the data shown, 1112°. to 21°. Two models are presented which fit these data. They differ only slightly and confirm the existence of discontinuities near 400 and 600 kilometers.
A method is described for predicting the effect on travel times of small changes in the Earth structure.
The frequency-magnitude relation of microfracturing in rock and its relation to earthquakes
Authors: Scholz C. H. 
Published: July 2021

abstractDuring the deformation of rock in laboratory experiments, small cracking events, i.e., microfractures, occur which radiate elastic waves in a manner similar to earthquakes. These radiations were detected during uniaxial and triaxial compression tests and their frequency-magnitude relation studied. They were found to obey the Gutenberg and Richter relationlog N = a + b MWhere N is the number of events which occurred of magnitude M, and a and b constants. The dependence of the parameter b on rock type, stress, and confining pressure was studied. It was found to depend primarily on stress, in a characteristic way. The frequency-magnitude relation for events which accompanied frictional sliding and deformation of a ductile rock was found to have a much higher b value than that observed in brittle rock. The Gutenberg and Richter formulation of the frequency-magnitude relation was derived from a statistical model of rock and crustal deformation. This analysis demonstrates the basis of similarity between rock deformation experiments in the laboratory and deformation of the crust.
Early earthquakes in North-Central Iran
Authors: Ambraseys N. N. 
Published: July 2021

Abstract
In this paper a comparison between historical earthquakes and recent seismic activity in northern Iran is presented. It is shown that for certain parts of the world which have a long well-documented history the problem of earthquake frequency can be solved approximately on the basis of seismic history and local tectonics. Considering the state of development of instrumental seismology and of its interpretation, it is not only inadequate to attempt the assessment of seismicity without due consideration to the earthquake history but it may also be misleading.