bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Hebgen Lake, Montana, earthquake of August 18, 1959: P waves
Authors: Ryall Alan 
Published: July 2021

ABSTRACT
The instrumental epicenter of the Hebgen Lake earthquake is found to lie within the region of surface faulting. The depth of focus had a maximum value of 25 kilometers.
Times of P are studied in detail for epicentral distances less than 13 degrees. The apparent scatter of arrival times from 700 to 1400 kilometers can be explained by variations of the velocity of Pn between the physiographic provinces of the western United States. A comparison of observations for the Hebgen Lake earthquake with published times for blasts in Nevada and Utah indicates that the velocity of Pn in the central and eastern Basin and Range is about 7.5 km/sec, and that the crust in that region thickens toward the east and thins toward the south. A comparison of apparent velocities in northern California, in directions parallel and transverse to the structure, indicates that the crust thins by about 19 kilometers, from the edge of the Sierra Nevada to the Pacific Ocean.
A discontinuity is observed in the travel-time curve at a distance of 24–25 degrees. Arrivals of P waves in the range 65–128 degrees fall on two parallel travel-time branches; this multiplicity in the travel-time curve may be related to repeated motion at the source. Travel-times of PKIKP appear to deviate from published curves.
The fault-plane solution for the Hebgen Lake earthquake, together with a consideration of the first motion at Bozeman, Montana, indicates a focal mechanism of the dipole, or fault, type. The strike and dip of the instrumental fault plane agree well with observed ruptures at the surface.
A special-purpose program for earthquake location with an electronic computer
Authors: Nordquist John M. 
Published: July 2021

ABSTRACT
An electronic digital computer program has been developed for determining the source and origin time of a local earthquake by the method of least squares, using the times of arrival of direct and refracted P waves at stations in the Pasadena network. Output includes the geographic coordinates and depth of the source, the origin time, direct distances from the source to each station, and the difference between observed and computed arrival time of P at each station. Limitations to the applicability of the program are discussed.
A hall-effect seismograph
Authors: Nałęcz Maciej , Zawicki Ignacy 
Published: July 2021

ABSTRACT
The principle of operation and the amplitude and phase frequency characteristics of a newtype seismograph are discussed and compared with those of an electrodynamic seismograph. The properties of this instrument allowing its use also as a tiltmeter are set forth. The action of the new seismograph is based on utilization of the Hall effect in semiconductors. Experimental results obtained with the new device are given.
A transient technique for seismograph calibration
Authors: Espinosa A. F. , Sutton G. H. , Miller H. J. 
Published: July 2021

abstract
A transient technique for seismograph calibration was developed and tested by a variety of methods. In the application of this technique a known transient in the form of an electrical signal is injected, through (a) a Willmore-type calibration bridge or (b) an independent coil, into the seismometer and the corresponding output transient of the system is recorded. The ratio of the Fourier transform of this transient to that of the input pulse yields phase and relative amplitude response of the seismograph as a function of period. Absolute amplitude response may be calculated if two easily determined constants of the seismometer are known. This technique makes practical the daily calibration of continuously-recording seismographs without disturbing the instruments more than a very few minutes. The transient technique was tested and proven satisfactory with results of more conventional steady-state methods, using both digital and analog analyses of the output transients.
A variety of output transients corresponding to various theoretical response curves has been calculated for two standard input transients. By comparison of the calculated output transients with experimental results it is possible to obtain the response of the instrument with considerable precision quickly and without computation.
The propagation of short elastic surface waves on a slowly rotating earth
Authors: Backus G. E. 
Published: July 2021

abstract
The effects of slow rotation with angular velocity Ω on Love and Rayleigh waves with given horizontal wave vector k on a plane-layered, transversely isotropic half-space have been calculated to first order in Ω. The frequency of Love waves is unaffected by rotation, while the frequency of Rayleigh waves is increased by k−1R(k)Ω · (z^ × k) where z^ is the unit outward normal to the boundary of the half-space and R(k) is a dimensionless function of k, the length of k. R(k) lies between −1 and 1, and vanishes identically for a homogeneous, isotropic halfspace with Poisson ratio 14. The vertical and longitudinal particle motions in a Love wave do not vanish and are neither in phase nor in quadrature with the transverse motion. The transverse particle motion in a Rayleigh wave does not vanish and is neither in phase nor in quadrature with the vertical and longitudinal motions.
It has been shown that a group of short, multicomponent waves on an anisotropic curved surface behaves like a classical particle, whose Hamiltonian is generated by the local dispersion relation and the curvilinear coordinates used to describe the surface. This extension of Hamilton's eikonal theory, together with the plane dispersion relations just derived, has been applied to Love and Rayleigh waves of given wave number k on a radially stratified, transversely isotropic sphere of radius a rotating slowly with angular velocity Ω. Correct to first order in Ω and (ak)−1, the trajectory of a Love wave group is unaffected by rotation, while the plane of the great circle trajectory of a Rayleigh wave group maintains its inclination to the axis of rotation and precesses about that axis with angular velocity (ak)−)R(k)Ω. Because of this precession, at a fixed seismograph the direction of arrival of 333 second mantle Rayleigh waves from a point impulsive source changes systematically by about 2R degrees after each circuit of the earth.
Concurrent storms of long and ultralong period microseisms
Authors: Oliver Jack , Page Robert 
Published: July 2021

AbstractStorms of ultralong period (14-18 seconds) microseisms are shown to be concurrent with storms of the more familiar long period (7-9 seconds) microseisms, and to be related to the same meteorological disturbances. Data from Palisades, New York, were analyzed for two cases, one for a meteorological storm over the northeastern Pacific and one for a meteorological storm in the northwestern Atlantic. The conclusions are based on correlation of continuous spectral analyses of the concurrent microseism storms, and on ground particle motion studies.The periods of the ultralong period microseisms at any given time are, within the precision of the measurements, twice the periods of the long period microseisms at that time.
Long period seismic waves from large, near-surface nuclear explosions
Authors: Pomeroy Paul W. 
Published: July 2021

Abstract
Seismic surface waves were well-recorded from the larger explosions of the U.S. test series detonated in the Marshall Islands during the spring and summer of 1958 and of the U. S. S. R. test series detonated at the Novaya Zemlaya test site during October 1958. In addition to waves of the fundamental Rayleigh mode, some unusual or unexpected waves were identified. These include: 1.) Love waves with lengths as great as 90 km at Hong Kong from the U. S. S. R. explosions, 2.) Love waves at Agra, India, from the U. S. S. R. explosions, 3.) waves of the 1st shear mode at Agra and Uppsala, Sweden, from the U. S. S. R. explosions, and 4.) Love, 1st shear and PL waves at Guam from the U. S. explosions.
Group velocity data were derived for many paths and, for the U. S. series, these data are very accurate because they are based on exact knowledge of locations and origin times. For the U. S. S. R. explosions, revised locations and origin times based on a limited number of P-wave observations were used to determine group velocities. Using records from Hong Kong and Honolulu for two U. S. tests, one at Eniwetok and one at Bikini, oceanic phase velocities in the period range of 15 to 40 seconds were measured for the path between these islands. Using Brune's method for initial phase determination with a known phase velocity, an initial phase, φ0, lying between +3π2 and +π2 was determined for the U.S. explosion, Oak. According to Aki (1960), these values of initial phase are associated, respectively, with forcing functions of a downward impulse and an explosive impulse.
Seismic magnitudes of 4.7 and 4.8 were assigned to the U. S. Oak and Poplar events on the basis of the surface wave data, while magnitudes of the larger U. S. S. R. tests range from about 4.0 to 4.5. The ratio of seismic energy as computed from the surface wave magnitude to the total explosive energy available (yield) is apparently greater for the U. S. explosions, assuming equal yield for the two shots compared. This suggests a higher altitude of detonation for the Russian events. The Fourier amplitude spectra of the surface wave trains are generally single peaked where a significant portion of the path traversed is oceanic, but for Uppsala, where the path is short and continental, a second peak occurs at periods of about 10 to 13 seconds. The ratios of the predicted amplitudes, based on the data of one station and on a reasonable dissipation factor, to the actual recorded amplitudes vary with azimuth by as much as a factor of 5. These variations may be explained by asymmetry at the source but might also be explained by instrumental and geologic factors. Long period components of P and S and multiples thereof were sometimes recorded from these events.
Crustal structure of Pacific Ocean area from dispersion of Rayleigh waves
Authors: Santô Tetsuo A. , Båth Markus 
Published: July 2021

Abstract
The dispersion of Rayleigh waves along a great number of Pacific paths has been studied by means of records from Pasadena, California, U. S. A., and Huancayo, Peru. Combining these measurements with previous ones based on records at Tsukuba, Hongkong, Honolulu and Suva, it was found that the central part of the Pacific Ocean exhibits the most oceanic structure, with exception for the Hawaiian Islands. In the south-eastern Pacific Ocean an area could be delineated with a new type of dispersion characteristics, not found in any other part of the Pacific. This area agrees closely with the Easter Island Ridge system, and exhibits unusually thin crust and low upper-mantle velocities as well as exceptionally high heat flow.
On detecting soft layers in the mantle with Rayleigh waves
Authors: Harkrider D. G. , Hales A. L. , Press F. 
Published: July 2021

Abstract
The feasibility of an experiment to detect soft or molten zones in the mantle using Rayleigh wave phase velocities is examined. It is found that when the anomalous zone has large lateral extent the phase velocity curves are so affected as to make it easily detectable. A discussion of dispersion curves and displacement with depth is presented. A pseudo-flexural mode of oscillation is found to be possible for the layers above a molten zone.
Processing of seismic data from an automatic digital recorder
Authors: Phinney Robert A. , Smith Stewart W. 
Published: July 2021

Abstract
Data from a three-component, long-period seismometer system is recorded in digital form on magnetic tape by a device which has been described by Miller. Preliminary editing and processing is performed to select events of interest from the 24-hour tapes and place them on a library tape that is compatible with a computer. Emphasis is placed on location, correction, and flagging of errors that occur during the recording and editing process. Processing routines developed include: correction for seismometer response, orbital motion functions, energy computation, band pass filtering for mode separation, etc. The dynamic range of the system is 86 db and the response is adequate over the range .02 to 2.0 cps. For the purpose of detailed analysis, digital records from this system are superior to paper records from any of the existing seismographs in use at this laboratory. The main disadvantage of data in this form is the difficulty of inspecting signals by eye in order to make preliminary interpretations.
Pn velocity and other seismic studies from the data of recent southeast Missouri earthquakes
Authors: Stauder William , Bollinger Gilbert 
Published: July 2021

Abstract
Five earthquakes occurred in the southeastern Missouri seismic region during the first seven months of 1962. The largest of these took place on 2 February 1962, and was located near New Madrid. The felt area of this shock covered 35,000 square miles; the maximum intensity was Intensity V in the Modified Mercalli scale. The magnitude is estimated to have been 4 1/2 to 4¾.
Pn arrival times from thirty-five stations in the distance range 200 km to 1000 km fit a composite travel time curve for all five earthquakes given by
t = 5.56 ± 0.21 sec ⁡ + Δ / ( 8.23 ± 0.02 km / sec ) .
This contrasts with interval velocities of 8.3 km/sec to 8.5 km/sec obtained by Herrin and Taggart for this region from the Gnome data. Sn and P and S crustal velocities are also studied.
Pulse-like Rayleigh and Love waves were also recorded, each indicating a group velocity maximum at a period of about 6 seconds. The amplitudes of each of these wave types vary strongly, and in an inverse relation, with azimuth about the source. Group velocities correlate with the sedimentary and upper crustal structure along the path.
Model studies of effects of near-source velocity discontinuities on first-motion patterns
Authors: Lavin P. M. , Howell B. F. 
Published: July 2021

Abstract
Directions and amplitudes of first compressional and shear motions were measured in two-dimensional plastic models from a simulated explosion, a unidirectional-force, a single-couple and a double-couple source. Patterns for a uniform circular model are compared with those for the source located on a boundary, near a boundary, in a low-velocity zone, and near a high-velocity region.
In general, the patterns for the uniform models are consistent with theory except that weak S waves were noted from the simulated explosion. Reversals of the first motions of P due to the presence of velocity discontinuities were observed within 30° of the boundary running through the double-couple source.
Amplitude reduction in the high-velocity medium of the non-uniform models leads to the possibility of missing the first motions. Under these conditions, “first-motion” patterns may be undependable as a means of determining the source mechanism. Thus, a single couple, double couple, and radial force may produce a single-force distribution and the single force may give a single-couple pattern.
Precision determination of focal depths and epicenters of local shocks in California
Authors: Cisternas Armando 
Published: July 2021

Abstract
A program for the location of hypocenters of local shocks by means of an electronic digital computer is described. The P times are corrected for variations in crustal structure to get precision in the determination of depth. An estimate of the accuracy of the method is given for some particular cases. Application of the program to the Kern County series of aftershocks, provides a clearer picture of tectonic mechanism of the White Wolf fault. A future extension of the program to process and correct data automatically is also described.
The tsunami of 22 May 1960, in the Samoa and Cook Islands
Authors: Keys J. G. 
Published: July 2021

ABSTRACT
The tsunami which reached islands of the Samoan group at approximately 2035 hours local time, 22 May 1960, was undoubtedly one of the largest that has been recorded in the group. Generated by a large earthquake off the coast of Chile (near 41 °S, 7312 °W) at 1911 hours Greenwich Mean Time (GMT), 22 May, the tsunami was responsible for widespread damage throughout the Pacific.
The tsunami which reached islands of the Samoan group at approximately 2035 hours local time, 22 May 1960, was undoubtedly one of the largest that has been recorded in the group. Generated by a large earthquake off the coast of Chile (near 41 °S, 7312 °W) at 1911 hours Greenwich Mean Time (GMT), 22 May, the tsunami was responsible for widespread damage throughout the Pacific.
The characteristics of the tsunami observed at Rarotonga in the Cook Islands are also described.
Effects of the earthquakes of May 1960 and geologic relations in Rio Negro
Authors: Thomas Herbert , Bowes William , Bravo S. Nelson , Moraga Aldo 
Published: July 2021

ABSTRACT
Damage to the town of Rio Negro was extensive along a long thin ridge lying between Rio Forrahue and Rio Llay-Llay and on the adjacent banks. The damage was largely produced by mass movement, although the actual oscillatory ground movement may have been greater on the higher parts of the ridge. A possible north-south fault is indicated. The subsoil is glacio-fluvial sands and gravels. Recommendations for reconstruction are given.
Modifications to the soil pattern of South-Central Chile resulting from seismic and associated phenomenona during the period May to August 1960
Authors: Wright Charles , Mella Arnoldo 
Published: July 2021

ABSTRACT
Genesis and evolution of soils in the earthquake region is discussed and then reviewed in the light of changes induced by the earthquakes. Those effects of the earthquake that could possibly influence soils are reported on in detail. These include many field observations on the mass movement, the tsunamis, flooding, changes in land elevation and regime of rivers, volcanic eruptions, etc. A catalogue of changes, including land lost to production completes the study.
(PStA)
Landslides at Lago Riñihue, Chile
Authors: Davis Stanley N. , Karzulovíc K. Juan 
Published: July 2021

ABSTRACT
Strong earthquakes of 22 May 1960 produced three large landslides which blocked the outlet of Lago Riñihue, 65 kilometers east of the city of Valdivia, Chile. The lake level rose 26.5 meters before water began discharging through artificially constructed canals during the last week in June, 1960. The largest landslide involved about 30 million cubic meters of unconsolidated sediments, the intermediate landslide about 6 million cubic meters, and the smallest landslide about 2 million cubic meters.
The surface of rupture of the largest landslide is within an 80-meter sequence of Pleistocene lake clays. The clays are underlain by till and overlain by outwash sands and gravels. Movement of the landslide is interpreted as having been principally block gliding and lateral spreading. Secondary landslides within the larger landslide were produced by rotational slumping, debris falls, and earth flows.
Several ancient landslides exist in the vicinity of Lago Riñihue, the largest involving more than 100 million cubic meters of unconsolidated sediments. Many of the older landslides also were probably triggered by earthquakes.
A frequency-velocity-energy diagram for the study of dispersive surface waves
Authors: Iyer H. M. 
Published: July 2021

abstract
A technique for displaying the dispersion effect of surface waves in terms of energy contours on a frequency-velocity diagram is described. Preliminary results from analysis of data from an earthquake in Chile as recorded in Sweden show that predominant Rayleigh phases occur at periods of 16 and 25 sec and the corresponding velocities are 2.9 and 3.5 km/sec respectively. A Love phase of period 40 sec and velocity 4.1 km/sec is also noticed. Spectral analysis and coherence studies confirm the formation of these phases. The results are preliminary and tend to illustrate the usefulness of the technique for analysis of surface waves from earthquakes.
The velocity of seismic waves near the earth's center
Authors: Bolt Bruce A. 
Published: July 2021

abstract
A double velocity jump in the Earth's core entails a PKP travel-time curve with two lengthy branches extending back from 143°. The later branch is associated with the PKIKP phase. The earlier branch arises from waves, here designated PKHKP, which are refracted through the intermediate shell.
Theoretical travel-time curves for PKP and SKS in possible Earth models with tripartite cores are presented. It is shown that the PKHKP branch provides an explanation for precursors to PKIKP observed at epicentral distances between 123° and 140°. Observations of waves predicted by the portion of this branch from 148° to 156° have been also reported. The SKS curve is examined in the light of some 550 SKS observations in the range 85° &lt; Δ &lt; 145°.
The study provides evidence that there is in the core a discrete shell with thickness of order 420 kms and with a mean P velocity near 10.31 km/sec. This shell surrounds the inner core having mean radius 1220 kms and mean P velocity 11.22 km/sec, approximately. The material of the intermediate shell is not likely to have marked rigidity. The inner core is likely to be solid; published times for PKJKP waves may be, however, too small by several minutes.
Strong ground motions recorded during earthquakes of May the 11th and 19th, 1962 in Mexico City
Authors: Zeevaert Leonardo 
Published: July 2021

abstract
The ground accelerations during the earthquakes of May 11 and 19, 1962 were recorded in Mexico City on a soft clay bed that was formerly the floor of an old lake. Records were obtained from two accelerometers, one instrument was located in the basement of a multistory building and the other was located in a nearby park. Response spectra of the ground motions are presented and analysis is made of the local soil conditions with the view to explaining the characteristics of the spectrums.
Radiation pattern of surface waves from point sources in a multi-layered medium
Authors: Haskell N. A. 
Published: July 2021

abstract
A previous treatment of the radiation pattern of Rayleigh waves from single and double couple point sources of arbitrary orientation in a semi-infinite homogeneous medium is generalized to the case of a medium composed of an arbitrary number of parallel homogeneous layers by the use of layer matrices. Source coefficients are given for a single force, a force dipole without torque, a single couple, and a double couple without torque, all for arbitrary orientation vectors, and also for a spherically symmetrical compressional source. For the simplest case permitting the existence of Love waves, a single finite layer over a semi-infinite medium, expressions for the Love wave radiation pattern are given explicitly in a form comparable to that previously given for Rayleigh waves in the homogeneous case.
Real-time, high resolution spectroscopy of seismic background noise
Authors: Walker R. A. , Menard J. Z. , Bogert B. P. 
Published: July 2021

ABSTRACT
The frequency-time-amplitude characteristics of seismic background noise at Chester, New Jersey have been studied for three years with high frequency resolution spectrum analyzers operating continuously in real time. Short-period (0.3 to 3.0 cps) and long-period (0.02 to 0.2 cps) bands have been analyzed simultaneously. In addition to the main microseism peak in the 6- to 8-second period region, secondary peaks are frequently observed at both longer and shorter periods. These usually persist for times on the order of days, often exhibit gradual shifts of center frequency, and show considerable variation in bandwidth; they are presumed to be of natural origin. In addition, several line components are found; these are believed to be of cultural origin, originating from a number of independent machines. Tape recordings from other U. S. seismic observatories have been analyzed, disclosing the presence of machinegenerated noise at several sites; notably, a strong spectral peak at 2 cps at the Wichita Mountains Seismological Observatory has been demonstrated to consist of a group of spectral lines.