bluuebunny/crossref_metadata_2025_split huggingface dataset:
Seismic wave arrivals from LONGSHOT, 0° to 27°
Authors: Carder D. S. , Tocher Don , Buee Charles , Stewart S. W. , Eisler Joseph , Berg Eduard 
Published: July 2021

abstract
Seismic wave arrivals from the LONGSHOT underground nuclear explosion were recorded at 27 locations in Alaska and two in Yukon Territory at distances between 2.6° and 26.6° from ground zero on Amchitka Island. Five of these stations were on the island chain, three on the Alaska Peninsula, two on other islands, and the remainder on the mainland from Anchorage to Point Barrow. The upper mantle travel times to distances of about 11° may be represented by t = Δ(km)/7.85 + 4.9 ± 0.5. The estimated depth to the M discontinity beneath the island chain is from 22 to 26 km depending on the choice of data.
In the distance range from 6° to 16°, recognition of the initial P wave may be a function of the signal-to-noise ratio. From 13° to 27°, travel times average from 1.5 to 4.0 seconds earlier than the JB surface-focus travel times with a steep gradient from “early” in central and northern Alaska to an average of 2 seconds “more early” in eastern Alaska including Circle Hot Springs, Anchorage, and Kodiak. PcP arrivals are recognized at 15.5° and beyond, and their travel times are parallel to the JB PcP times but are from 2 to 4 seconds earlier. PcP was not anomalously early at Kodiak as was P. P wave amplitude maxima to the Bering Sea stations of St. Paul Island and Cape Romanzoff were an order less than at like distances on the Peninsula.
Gravitationally perturbed elastic waves
Authors: Gilbert Freeman 
Published: July 2021

abstract
In Lamb's problem there are two interface pulses. When the half-space is incompressible the locked Rayleigh (S) pulse travels with a speed γ = 0.9553β where β is the shear pulse speed, and the leaking Rayleigh (P) pulse travels with a speed δ = 1.966β. In the absence of gravity the S pulse is the more dominant pulse. The effect of gravity is to enhance the importance of the P pulse. In the presence of gravity, as β decreases, the S pulse becomes insignificant, and the P pulse becomes dispersive and approaches the behavior of the classical gravity wave. Several theoretical seismograms and hodographs, for the buried line source problem, are presented to illustrate the effect of gravity.
The effect of gravity on dispersion curves, for a layer with a rigid bottom, is to distort them in such a way that one should observe wave groups similar to the classical gravity waves in a fluid layer when the shear speed is small. In addition one should observe very slow wave groups with wavelengths shortened by gravity. Several dispersion curves are presented to illustrate these features.
The propagator coefficient matrix is given for a transversely isotropic material including gravity.
Analysis of current methods of interpreting strong-motion accelerograms
Authors: Schiff Anshel , Bogdanoff John L. 
Published: July 2021

abstract
The influence on the calculated velocity and displacement and shock spectra of accelerogram vagaries is examined. The effect of centerline adjustment, small random reading errors, and chart paper distortion are considered in detail. An expression for the variance of the final displacement error, which is caused by accelerogram reading errors, is presented. This expression can be used to determine the reading accuracy required to evaluate the final ground displacement to desired accuracy. The utility of determining ground velocity and displacement is discussed. The effects of accelerogram reading errors on shock spectra is considered. The adequacy of current chart paper speeds and transducer natural frequencies is discussed.
It is concluded: (a) that the use of accelerograms to accurately determine net ground displacement is impractical; (b) that reading errors in accelerogram charts, as they are currently being recorded, can cause significant errors in response spectra; (c) that limitations of current seismographs may attenuate the high frequency content in strong-motion seismic shocks or distort low-frequency spectra due to aliasing.
A model study of elastic waves in a layered sphere
Authors: Gregson Victor 
Published: July 2021

abstract
Elastic waves produced by an impact were recorded at the surface of a solid 12.0 inch diameter steel sphere coated with a 0.3 inch copper layer. Conventional modeling techniques employing both compressional and shear piezoelectric transducers were used to record elastic waves for one millisecond at various points around the great circle of the sphere. Body, PL, and surface waves were observed. Density, layer thickness, compressional and shear-wave velocities were measured so that accurate surface-wave dispersion curves could be computed. Surface-wave dispersion was measured as well as computed.
Measured PL mode dispersion compared favorably with theoretical computations. In addition, dispersion curves for Rayleigh, Stoneley, and Love modes were computed. Measured surface-wave dispersion showed Rayleigh and Love modes were observed but not Stoneley modes. Measured dispersion compared favorably with theoretical computations. The curvature correction applied to dispersion calculations in a flat space has been estimated to correct dispersion values at long-wave lengths to about one per cent of correct dispersion in a spherical model. Measured dispersion compared with such flat space dispersion corrected for curvature proved accurate within one per cent at long wave lengths.
Two sets of surface waves were observed. One set was associated with body waves radiating outward from impact. The other set was associated with body waves reflecting at the pole opposite impact. For each set of surface waves, measured dispersion compared favorably with computed dispersion.
Surface motion from pulse transmission through anisotropic layered structures
Authors: Robinson Edwin S. , Costain John K. 
Published: July 2021

abstract
Theoretical surface motion for pulse transmission through transversely isotropic elastic structures is computed by Fourier inversion of the product of the Fourier transform of an input pulse, complex transfer coefficients for anisotropic structures, and a seismograph system response. Introduction of anisotropy causes subtle changes in the angles of refraction and shifts in arrival times of different phases as intuitively expected from Snell's law. Computations suggest no obvious criteria for recognizing anisotropy from surface motion.
Standing waves in layered fluid half-space
Authors: Gupta I. N. 
Published: July 2021

abstract
The existence of standing waves in a horizontally-layered fluid half-space is established for plane harmonic compressional waves propagating from below. The angle of incidence and the velocity-distribution within the layers are assumed to be arbitrary. Expressions are derived for the particle velocity at the free surface and at any given depth. The results show features similar to those for normally incident waves in a multilayered solid half space.
Travel-time curves and upper-mantle structure from long period S waves
Authors: Ibrahim Abou-Bakr K. , Nuttli Otto W. 
Published: July 2021

abstract
Long-period S-wave travel-time data, including second and later arrivals, are presented for distances of 3° to 65° for focal depths of 33 and 120 km. Onset times were determined on the basis of particle motion diagrams and the product of the horizontal radial and vertical components of motion. Because the recording stations principally were LRSM units, the travel times represent data for an “average” United States earth model.
An S-wave velocity distribution calculated for the upper mantle provides a satisfactory fit to the empirical travel-time data for focal depths of both 33 and 120 km. The proposed model contains a pronounced low-velocity layer at a depth of about 150-200 km, and secondary low-velocity layers at depths of 340-370 km and of 670-710 km. In addition, there are regions of rapidly increasing velocity beginning at depths of about 400 and 750 km, and constant velocity zones at 220-350 km and 400-670 km.
Intensity map and structural damage, Parkfield, California earthquake of June 27, 1966
Authors: Cloud William K. 
Published: July 2021

Abstract
The isoseismal map indicates that the main shock of the Parkfield, California earthquake series on June 27, 1966 was felt over an area of approximately 20,000 square miles, and that the maximum Modified Mercalli scale intensity of VII was limited to a small area near the San Andreas fault zone in the vicinity of the Parkfield and Cholame. In this area an acceleration pulse of 0.5g was recorded. However, damage to homes, pipe lines, bridges and other structures was not severe.
Love wave spectra and the mechanism of the 1966 Parkfield sequence
Authors: Filson John , McEvilly Thomas V. 
Published: July 2021

AbstractThe spectra of the Love waves from five earthquakes of the 1966 Parkfield sequence, recorded at Berkeley, have been studied for evidence of source propagation. Independent field evidence suggests that the source of the main shock of the sequence may have propagated on a line away from Berkeley. The modulation effect of propagation on the amplitude spectrum is discussed. This effect is dependent upon the total time delay due to rupture down the fault and seismic wave propagation back to the point of initial rupture, and is thus ambiguous with respect to fault rupture velocity and fault length. Consideration of a frequency dependent phase velocity can resolve this ambiguity. The amplitude spectrum of the largest (M = 5.5) Parkfield earthquake shows sharp minima at periods where the spectra of the other four shocks are relatively smooth. Considered individually, these minima are consistent with a fault rupture length of about 30 km and a rupture velocity of 2.2 km/sec. The pattern of the minima varies from that predicted by the assumed phase velocities, thus the rupture velocity/fault length ambiguity is not resolved. Similarity in the shape of the spectra of the four smaller (M = 3.8-5.1) events suggests similar focal dimensions for these earthquakes. The Love wave amplitude spectra of the four smaller earthquakes scale well, at intermediate periods, to the magnitudes determined on standard short-period intruments; the main shock scales to a much higher magnitude. The spectra are considered in the light of proposed seismic scaling laws.
Note on strong motion records from the June 1966 Parkfield, California, earthquake sequence
Authors: Murray G. F. 
Published: July 2021

AbstractData is presented for all the June 1966 Parkfield, California, earthquakes that were recorded by five strong motion accelerographs in the Shandon-Cholame area south of Parkfield. The instrument array is generally transverse to the fault, intersecting it just north of the southern limit of the June surface fractures. Unique seismograms were obtained of small shocks during wave motion from the principal earthquake; in the three minutes following the onset at 0426, June 28 GMT, two of the strong motion instruments recorded completely ten different earthquakes. Approximate epicenters are located for thirteen of the earthquakes.
T-phase radiators in the western Aleutians
Authors: Johnson Rockne H. , Norris Roger A. 
Published: July 2021

abstract
The aftershocks of the Rat Islands earthquake of 4 February 1965 provided a large volume of data for processing with a T-phase source location program. Although the earthquake epicenters were somewhat uniformly distributed through the Rat and Near Islands region, the computed T-phase sources were grouped in six clusters along the Aleutian arc. The clusters are considered to represent radiation from distinct sites along the Aleutian Ridge. These sites are probably submarine promontories which, due to their exposure, radiate energy over broader arcs of the Pacific than do intervening regions. The relationship of T-phase strength to earthquake magnitude varied little among these radiators; however, T phases from sources south of the Aleutian trench were significantly weaker. Identification of the arrivals from separate radiators in the signal from the main shock allowed an estimation of the length and velocity of the faulting. The estimate was 500 km and 3.5 km/sec.
Earthquake of August 19, 1966, Varto Area, eastern Turkey
Authors: Wallace Robert E. 
Published: July 2021

abstract
The earthquake of August 19, 1966, centered near Varto in eastern Turkey. It occurred at 12:22:09.6 G. M. T. and had a Richter magnitude of about 7. Intensities reached IX. Reportedly, 2,529 people were killed, 1,500 injured, and 19,013 buildings were demolished or heavily damaged.
Surface fractures in three parallel fracture zones trending N65-70°W display both right-lateral strike slip and extension normal to the fractures. The trend and sense of displacement relate the fracturing to the North Anatolia fault system.
Examples of geologic factors influencing damage include: (1) degree of saturation of the alluvium, (2) proximity to landslides, and (3) relation to surface faulting.
Effect of anisotropy on Love wave propagation
Authors: Negi Janardan G. , Upadhyay S. K. 
Published: July 2021

abstract
A study on Love wave propagation in a transversely isotropic layer with stress free upper surface and underlying rigid base, is presented. The characteristic frequency equation is obtained and frequency dependence of the velocity parameters for different modes is analysed in detail. Several distinctive propagation phenomena which differ considerably from those in isotropic case are listed below:
A photoelastic analysis of propagation of Rayleigh waves past a step change in elevation
Authors: Dally J. W. , Lewis David 
Published: July 2021

Abstract
A series of photoelastic tests were conducted to determine transmission and reflection coefficients associated with the stress and displacement of a Rayleigh wave propagating past a step change in elevation on the boundary of an elastic half plane. The determinations were made on six different models with ratios of step height to wave length (h/λ) ranging from 0 to 1.1. The stress transmission coefficient varied from 1 to about 1.5 as h/λ increased from 0 to 1.1. The stress reflection coefficient increased from 0 to 0.7 with increasing h/λ. The displacement transmission coefficient increased initially to a value of 1.4 for h/λ = 0.2 then decreased monotonically to about 1 as h/λ increased to 1.1. Finally, the displacement reflection coefficient increased monotonically from 0 to about 1.5 as h/λ increased over the range considered.
The photoelastic method provides information over the entire region of interest which is very useful in the understanding and analysis of the complex wave interaction problems associated with Rayleigh wave propagation past boundary irregularities.
Minimum recording times for determining short-term seismicity from microearthquake activity
Authors: Sanford Allan R. , Singh Surendra 
Published: July 2021

Abstract
The minimum microearthquake recording time needed to determine short-term seismicity (10 years) has been established for regions having the same degree of activity as Socorro (400 shocks with M ≧ 0 each year). An analysis of more than five years of microearthquake data indicates that about six months of recording are required for a reliable estimate of the earthquake-frequency relation from which seismicity is calculated. If the slope b of the earthquake-frequency law is assumed, the short-term seismicity can be determined from four weeks of recording. The danger in the latter method is that a small error in b leads to relatively large errors in seismicity.
Long-term seismicity (100 years) predicted from the present level of micro-earthquake activity in Socorro is much lower than the known seismicity of the region. The number of microearthquakes would have to increase by a factor of 20, or the value of b decrease approximately 20 per cent, before prediction would agree with the long-term seismic activity of the region.
The Peru earthquake of October 17, 1966
Authors: Lomnitz Cinna , Cabré Ramón 
Published: July 2021

Abstract
Seismological results on the destructive Peru earthquake (M = 7.5) include: determination of epicenter, isoseismal map, tsunami observations, and some correlations between intensity and geologic factors. The epicenter was located off the coast of central Peru, about 190 kilometers northwest of Lima. Isoseismals were elongated in the direction of the coast line. The intensity exceeded VIII in the region of Huacho, and reached VII in Lima. There are indications, however, that accelerations and frequencies were both higher than would be expected in the regions for which the Modified Mercalli Scale was developed. Local high intensities were frequently correlated with the occurrence of recent alluvium. Analysis of tsunami travel times shows that the Peru Trench acts as a high-velocity channel which refracts wave energy to the coast in advance of the expected arrival over the direct path.
The East Coast Onshore-Offshore Experiment, II. Seismic refraction measurements on the continental shelf between Cape Hatteras and Cape Fear
Authors: Dowling John J. 
Published: July 2021

abstract
During the East Coast OnShore-OffShore Experiment (ECOOE) two lines of instrumented buoys were anchored on the continental shelf between Cape Hatteras and Cape Fear. One line extended from near shore to the 100 fathom depth contour. The other line was parallel to and near the 100 fathom depth contour. Shots varying in size from 20 lbs. to 10 tons were fired along both lines. From the refraction data obtained and well-control available, crystalline basement is correlated with a layer of velocity 5.96 km/sec, the top of the Lower Cretaceous with a layer of velocity 3.54 km/sec and the top of the Upper Cretaceous with a layer of 2.44 km/sec. A contour map of the depth to crystalline basement under the shelf and structure sections are presented. The statistical uncertainties in the depths and velocities were determined.
Preliminary report on some aftershocks of the December 28, 1966 earthquake in Northern Chile
Authors: Pitt Andrew M. , Ellis James O. 
Published: July 2021

abstractEpicenters of aftershocks of the December 28, 1966 earthquake in northern Chile lie in a 75-km north-trending zone 20 to 30 km off the coastline. The epicenter for the main shock, as determined by the U.S. Coast and Geodetic Survey, is about 10 km north of the southern end of the aftershock zone. The aftershocks are about 30 km deep in the model used for locations; this places them in the lower crust or upper mantle. The aftershocks have no apparent relation to any surface faults.
Effect of soil conditions on damage in the Peru earthquake of October 17, 1966
Authors: Lee Kenneth L. , Monge E. Joaquin 
Published: July 2021

abstractThis earthquake was centered offshore, 140 miles north of Lima. A strong motion record at Lima indicated a peak acceleration of 0.4g, and several pulses of 0.3g. The earthquake caused severe damage to many adobe and quincha houses and to some modern reinforced concrete structures in Lima, where the observed damage indicated MM intensities from VI to VIII. At towns closer to the instrumental epicenter the MM intensities ranged up to a maximum of about IX. There was some indication that the higher intensities were associated with the poorer soil foundation conditions. This was especially true where the soil and foundation conditions were particularly bad, but the trend was less definite where the soils provided good to fair foundations. Damage to well built tall buildings and other modern structures was mostly limited to broken windows and cracking in wall panels. In the few cases where modern structures did sustain more serious damage, it appeared to be due to inadequate provision for seismic forces in the designs, or to poor construction practices. Some slumping and landslides developed in dry sands and partially cemented granular soils.
A local magnitude scale for South Austalian earthquakes
Authors: White R. E. 
Published: July 2021

abstract
A magnitude scale has been developed for South Australian earthquakes which is simple and consistent. It is based on the maximum trace amplitude among the S waves recorded on vertical component Benioff seismographs, and applies to distances up to 3.6 degrees. The extension of the Richter local magnitude scale to Benioff and other highly sensitive instruments used to study small magnitude earthquakes and with no consideration of differences in crustal structure has drawbacks and, in the present case, could lead to significantly erroneous estimates of magnitudes. The South Australian scale has resulted from an application of the “time-term” method to the study of amplitudes. This has produced satisfactory agreement with a theoretical amplitude-distance relation. Tentative relations are given between the South Australian scale and other scales and an energy-magnitude relation is derived. The maximum S ground velocity between 1° and 3° is due to the reflection from the Mohorovičić discontinuity.
Computational methods
Authors: Engdahl Eric R. , Taggart James , Lobdell John L. , Arnold E. P. , Clawson Gerald E. 
Published: July 2021

Abstract
The surface-focus P travel times estimated by Herrin et al (1968) entail a P velocity distribution from which smoothed travel-time tables of P, pP, PP and PcP are constructed. Theoretical considerations and computational procedures used are described. It is shown that computational errors in the new travel-time tables are less than 0.01 second.
The response of the horizontal pendulum seismometer to Rayleigh and Love waves, tilt, and free oscillations of the earth
Authors: Rodgers P. W. 
Published: July 2021

Abstract
The horizontal pendulum seismometer is sensitive not only to acceleration along its sensitive axis but also to tilt, variations in the angle of inclination, and along-the-boom acceleration. The complete steady-state response of this type of seismometer to Rayleigh and Love waves, tilt, and free oscillations of the Earth is treated. An equation of motion is developed which includes the effects of tilt, variation in the angle of inclination, and along-the-boom acceleration. An approximate solution to this equation is obtained which separates out the response due to each effect. The response, including these effects, is developed for Rayleigh and Love waves and the conditions under which along-the-boom acceleration and variations in the angle of inclination are important are stated. The question “How much of the seismogram is due to tilt?” is answered in detail for long period Rayleigh waves and free oscillations. It is shown that the seismograms resulting from such waves can require sizable corrections depending on the wave parameters. A correction factor for Rayleigh waves is developed which is universal in the sense that it is independent of the parameters of the particular seismometer and thus applies to all pendulous horizontal seismographs. For Rayleigh waves it is a function only of ellipticity, phase velocity, and period. Correction factor curves for long-period retrograde Rayleigh waves are presented. For circular particle motions a ten per cent correction is required for a three hundred second Rayleigh wave. The problem of obtaining the horizontal ground motion is treated. The response of the horizontal seismometer as a tilt meter is examined; a conversion factor between displacement and tilt magnification is developed. The complete response to simultaneous spheroidal and torsional free oscillations of the Earth is developed. It is shown that the principal response to the low-order spheroidal modes is as a tilt meter. The relationship between the horizontal and vertical seismogram is developed.