bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vibration and soil-structure interaction tests of a nine-story reinforced concrete building
Authors: Jennings Paul C. , Kuroiwa Julio H. 
Published: July 2021

abstract
The Millikan Library Building, a nine-story reinforced concrete shear-wall structure at the California Institute of Technology, was tested dynamically by means of two eccentric mass vibration generators located on the ninth floor. The response levels ranged up to a maximum acceleration of 0:02 g. The natural periods of vibration, the mode shapes and the energy dissipation were measured for the first and second E-W translational modes, the N-S fundamental mode and the first torsional mode. Soil-structure interaction was investigated by measuring foundation motion and nearby soil surface movements during resonent vibrations in the N-S and E-W fundamental modes. Other tests included “man-excited” vibrations at low stress levels and a measurement of resonance of an air handling unit on the roof, which was found to magnify the roof response by a factor of 8.5.
The measured fundamental periods were short compared to typical framed structures of this height, 0.50 sec in the N-S direction, 0.66 in the E-W direction and 0.46 in torsion. These values increased roughly 3 per cent over the range of testing. The energy dissipation as measured by a viscous damping factor, varied between 0.70 and 2.00 per cent of critical. This large variation over the testing range indicates that tests at higher stresses are needed to determine the energy dissipation expected during the response to strong earthquake motions.
The soil-structure interaction measurements showed that the building responded very nearly as if fixed at the foundation; rocking contributed less than 1 per cent to the total roof motions of the structure and foundation translation about 2 per cent. Although negligible as far as the building motion is concerned, the results demonstrate the possibility of performing full-scale soil-structure interaction experiments.
A source of damping produced by the interaction of close-standing buildings
Authors: Rea Dixon , Bouwkamp Jack G. 
Published: July 2021

abstract
A multi-story steel-framed building was subjected to dynamic tests at various stages of construction. In the interval between two test series, a dramatic change occurred in the building's dynamic properties. In the first series, the damping capacities of the two fundamental modes (East-West and North-South) were about 2 per cent of critical; of the other modes, 0.4 per cent to 0.9 per cent of critical. In the second test series, the damping capacities of all modes ranged from 5 per cent to 10 per cent of critical.
This increase in damping has been attributed to the interaction of the building with its service tower. The second test series was conducted after the service tower was structurally complete. The two buildings were found to be dynamically coupled, with connections at only the basement and foundation levels. Non-structural connections, in the form of steel plates providing access between the buildings, existed at every floor level and dissipated energy in relative motion between the buildings. From experimental data it was possible to estimate the amount of energy this source of Coulomb damping could dissipate and to show that it was responsible for the large change noted in damping capacity.
Head waves from a transition layer
Authors: Nakamura Yosio 
Published: July 2021

abstract
Ultrasonic, seismic-model experiments have been performed to re-examine the nature of head waves from a transition layer. Two-dimensional, layered structures, some with a transition zone and some with a sharp discontinuity, constructed by lead-aluminum laminations have served as the models. Amplitude and phase responses have been measured in a frequency range of 25 kHz to 200 kHz. At low frequencies, where the wavelength is much longer than the thickness of the transition zone, little difference is observed between head waves from a transition zone and those from a sharp discontinuity. At a certain frequency range where the wavelength is close to the thickness of the transition zone, the measured head-wave amplitude from a transition zone becomes a few times larger than that from a sharp discontinuity. This is characteristic of head waves from a poorly defined boundary and may be used to estimate the thickness of a general transition layer. A sharp, high-frequency cutoff is again observed, but the cutoff frequency is not consistent with previous studies.
New techniques for the determination of surface wave phase velocities
Authors: Bloch S. , Hales A. L. 
Published: July 2021

abstract
A number of new techniques have been developed for the determination of phase velocities from the digitized seismograms from pairs of stations. One of these techniques is to Fourier analyze the sum (or difference) of the two seismograms after time shifting in steps to correspond to steps in phase velocity. The amplitude of the summed seismogram is a maximum for any particular period when both seismograms are in phase at that period. Another method is to pass both seismograms through a narrow bandpass digital filter centered at various periods and form the cross product of the filtered seismograms, after time shifting. The average of the resultant time series is a maximum when the two signals are in phase. The computer output is a matrix consisting of amplitudes or averages as a function of phase velocity and period. The phase velocity dispersion is determined from the contoured matrix. Using these techniques, interstation phase velocities of Rayleigh waves have been determined for the “World Wide Network Standard Stations” at Pretoria, Bulawayo and Windhoek. The method using cross-products is the most efficient.
Diffraction of elastic waves by a rigid 90° wedge Part I
Authors: Kraut Edgar A. 
Published: July 2021

abstract
The problem of calculating the reflected and diffracted elastic waves generated when a plane compressional wave strikes a rigid quarter plane is formulated as a Wiener-Hopf problem in two complex variables. It is shown how a closed form solution of this two variable Wiener-Hopf problem can be obtained provided that the Laplace transform of the elastic wave Green's function can be factorized into factors having suitable analytic properties.
Seismological measurements and measurement error
Authors: Freedman Helen W. 
Published: July 2021

AbstractA seismological measurement, such as arrival time or, less directly origin time, is an example of a measurement variable which can be considered as the sum of a parameter—the quantity being measured—and an error variable. Optimal methods for the estimation of this parameter vary with the probability distribution of the error variable. In particular, estimation in the presence of bias or of gross errors is discussed, together with the related problem of precision versus accuracy of the estimate.Errors in estimates of arrival times, origin times and hypocentral location contribute to variation in travel-time estimates; these are analyzed separately. Each of these, with the exception of focal depth, has a distribution which can be fitted to a mixture of a normal distribution and some contamination. The degree of contamination varies; methods for truncation are suggested. The presence of possible, often undetectable, bias in locations and travel times may make confidence statements about these parameters unreliable.
Estimation ofPKPtravel times
Authors: Bolt Bruce A. 
Published: July 2021

AbstractA set of travel times for the core-waves PKP is derived from observations and tabulated. All values are tied to the 1968 P travel times for a surface-focus for 75° &lt; Δ &lt; 95° due to Herrin et al. Times for both the branches DF (110° &lt; Δ &lt; 180°) and GH (125° &lt; Δ &lt; 156°) are listed in more detail than previously, together with an extension for PKiKP waves, from 110° back to 105°. Checks on the DF branch for 120° &lt; ° &lt; 150° using observations from the 1965 LONGSHOT explosion provide no evidence for further revision of the first section of this branch.Special attention is given to the times of the DF branch (PKIKP) for ° &gt; 150°. Delays at 153° and 162° of order 3 sec reported by K. Ergin in 1967 are not confirmed. There is a group of small arrivals about 1 sec earlier than predicted by the present PKIKP tables for 156° &lt; Δ &lt; 160°, approximately. These may indicate an error in the curvature of the present curve and, perhaps, a slight discontinuity in the inner core near a radius of 850 km. No evidence is found for a layer of any consequence with reduced P velocity in the inner core.Revised times for the branch AB (denoted by PKP2) are based mainly on readings from the Indian Ocean earthquake of February 17, 1966 and the Jeffreys-Bullen times. For Δ &gt; 155°, the new empirical times confirm the curvature of the Jeffreys-Bullen curve for PKP2; however, near Δ = 152°, the observed curvature appears to be greater than that of the latter curve. The new times are of the order of one second earlier; this result is highly sensitive to the precision of the epicenter estimated for the 1966 shock. PKP2 is traceable at least out to 185°.Depth allowances for PKP have been computed, by T. Qamar, to provide a set consistent with the model Earth used by Herrin et al in the 1968 P tables.
Epicentral uncertainties and detection probabilities from the Yellowknife seismic array data
Authors: Manchee E. B. , Weichert D. H. 
Published: July 2021

Abstract
Analog recording tapes from the Yellowknife seismic array have been processed diqitally in Canada for over a year, with concentration on the automatic detection and epicenter location of events between 26° and 90° distance, using short period P-wave arrivals.
For the purpose of detection, signals from the individual seismometers in the two arms of the cross array are analog band-pass filtered, digitized at 20 samples/s, multiplexed into a digital computer, velocity and azimuth filtered and correlated, using an exponentially weighted integration over time with an equivalent width of 1.6 s. The correlograms for up to 168 phased beams are scanned for values exceeding a preset trigger level and an event is recorded when the level is passed consistently a number of times. In late 1966, during a seismically quiet period and with the array fully operational, the 50 per cent automatic detection level achieved by this method for events in the Third Zone to Yellowknife was m4.0 ± 0.1, slightly better than the level of an analog trigger operated at the station which uses the correlogram method for a single unphased beam only. The 50 per cent detection level of the Yellowknife standard station is about m4.4 and thus the array-computer automatic detection method gives about Δm0.4 improvement, which is expected from the processing method used if the noise is largely uncorrelated. No significant variations in the detection level with azimuth have yet been observed.
Approximate epicenter locations are determined from the best apparent arrival vector. The best vector is assumed to be given by the maxima of parabolas at constant azimuth and wave number interpolated between the highest values of the correlograms.
USCGS P.D.E. information is used in conjunction with the J-B tables to calculate an expected apparent arrival vector. The difference between the expected and best interpolated arrival vectors has an average deviation of about 6 ms/km. Their distribution does not suggest a simple crustal or upper mantle cause under the array station.
Theoretical changes in seismic travel time with changes in stress at depth
Authors: Sawyers Kenneth N. 
Published: July 2021

Abstract
Use is made of second-order elasticity theory to derive an estimate of the change in travel time with stress for compressional waves which propagate along the principal stress directions in a homogeneous layer of material. A particular stress system is chosen which can be expected to produce a strike-slip fault. Laboratory data for Barre, Vt. granite, interpolated for a depth of approximately 1 km, are used to obtain a numerical result. The change in travel time is found to be 0.075 milliseconds per km per bar. Since timing precision of better than ±1 millisecond can be achieved for refraction paths up to some 40 km in length, it is concluded that stress changes of several bars are within the range of detectability in carefully executed field experiments.
Displacement on the San Andreas fault subsequent to the 1966 Parkfield earthquake
Authors: Smith Stewart W. , Wyss Max 
Published: July 2021

ABSTRACT
Immediately following the 1966 Parkfield earthquake a continuing program of fault displacement measurements was undertaken, and several types of instruments were installed in the fault zone to monitor ground motion. In the year subsequent to the earthquake a maximum of at least 20 cm of displacement occurred on a 30 km section of the San Andreas fault, which far exceeded the surficial displacement at the time of the earthquake. The rate of displacement decreased logarithmically during this period in a manner similar to that of the decrease in aftershock activity. After the initial high rate of activity it could be seen that most of the displacement was occurring in 4–6 day epochs of rapid creep following local aftershocks. The variation of fault displacement along the surface trace was measured and shown to be consistent with a vertidal fault surface 44 km long and 14 km deep, along which a shear stress of 2.4 bars was relieved.
Shear waves from a nuclear explosion in a salt cavity
Authors: Perret William R. 
Published: July 2021

ABSTRACT
Shear waves have been resolved in records of acceleration and particle velocity resulting from the Sterling event which was a nuclear explosion (380 tons) within the stable cavity left by the Salmon detonation in the Tatum salt dome. These shear waves were strongest in records of vertical motion at stations in the shot-level plane, but were detectable in records from both vertical and horizontal radial gages above and below that elevation. No appreciable shear waves could be identified in records from shot-level gages oriented horizontally. All instruments involved in this study were situated within the salt dome at ranges between 166 and 660 meters from the explosive source. Shear waves carried over 95 per cent of the energy in vertical shot-level records, but they represented less than 11 per cent of the energy in horizontal radial shot-level records. Cause of the vertically polarized shear waves is considered to be vertical asymmetry at the source.
Liquefaction of soils induced by earthquakes
Authors: Ambraseys N. , Sarma S. 
Published: July 2021

abstract
The conditions under which liquefaction effects are known to have occurred are reviewed and their generic cause is discussed. Special attention is given to the delay with which liquefaction effects appear on surface deposits originally stable. It is suggested that little damage to structures on poor soil can occur as the direct result of severe earthquake shaking and that damage observed is almost entirely due to foundation failures, ground settlements and tilting. Field evidence suggests that earthquakes are incapable of densifying originally loose deposits to a stable mass, and that such deposits neither experience nor transmit severe shaking.
Rays and travel times in a spherical anisotropic earth
Authors: Vlaar N. J. 
Published: July 2021

abstract
A study is made of the propagation of stress discontinuities (wave fronts) in a radially inhomogeneous, tangentially isotropic model of an anisotropic spherical medium.
The results are given in the form of integrals for the ray paths and the travel times for the several body-wave phases.
A special case of anisotropy dealt with in Section 2.2 (3) gives rise to considerable simplifications. This case in particular appears to be useful for the construction of travel-time tables for an Earth in which anisotropy occurs.
A study of the Koyna earthquake of December 10, 1967
Authors: Gupta Harsh , Narain Hari , Rastogi B. K. , Mohan Indra 
Published: July 2021

abstract
Data now available on the Koyna earthquake have been studied in detail. Different origin times and epicenters given by India Meteorological Department and Central Water and Power Research Station, field evidences and nature of the seismograms for this earthquake suggest a multiple event. A fault plane solution has been obtained by using the sense of first motions. Seismicity in Koyna region has been found to increase with the increase of water level in the reservoir and vice-versa with a certain time lag. The two major earthquakes of this region have similar foreshock-aftershock pattern, corresponding to type 2 of Mogi's (1963) models. Aftershocks of this earthquake are related by a function Log N = a + bM, value of b being −0.8. Possibility of predicting maximum expected magnitude at a certain seismic activity level of Koyna region has been also pointed out.
A note on the statistical interpretation of Båth's law
Authors: Vere-Jones D. 
Published: July 2021

Abstract
A theoretical version of Båth's law is derived on the assumption that aftershock magnitudes are independently and exponentially distributed. The results are not fully in agreement with the commonly accepted picture of Båth's law, but it is shown by reference to Utsu's table of Japanese aftershock sequences that the discrepancies may be due to bias introduced by the method of selecting the data for study.
Beam-steering of large randomly-spaced long-period arrays
Authors: Evernden Jack F. 
Published: July 2021

Abstract
Beam-steering of a U.S.-wide randomly-spaced array of long-period LRSM instruments is shown to yield a √n gain in signal to noise ratio for P signals and somewhat less for S signals. Bandpass filtering of these records yields an additional factor of 2 gain in signal to noise ratio.
Upper mantle structure in the Basin and Range province, western North America, from the apparent velocities of S waves
Authors: Kovach Robert L. , Robinson Russell 
Published: July 2021

Abstract
The variation of shear velocity with depth in the upper mantle for the Basin and Range province of western North America has been studied with direct measurements of dT/dΔ for S waves in the distance range 14° &lt; Δ &lt; 40°. Three orthogonal components of digital data were used and onset times were determined using the product of the horizontal radial and vertical components of motion and particle motion diagrams. A linear LRSM array in Arizona was used for the measurement of dT/dΔ.
An S-wave velocity distribution is derived, compatible with P-wave velocity models for the same region. The derived model consists of a thin lid zone of shear velocity 4.5 km/sec overlying a low-velocity zone and a change in velocity gradient at a depth of 160 km. Two regions of high-velocity gradient are located at depths beginning at 360 km and 620 km.
Universal dispersion tables
Authors: Anderson Don L. , Kovach Robert L. 
Published: July 2021

AbstractThe effect of a small change in any parameter of a realistic Earth model on the periods of free oscillation is computed for both spheroidal and torsional modes. The normalized partial derivatives, or variational parameters, are given as a function of order number and depth in the Earth. For a given mode it can immediately be seen which parameters and which regions of the Earth are controlling the period of free oscillation. Except for oSo and its overtones the low-order free oscillations are relatively insensitive to properties of the core. The shear velocity of the mantle is the dominant parameter controlling the periods of free oscillation and density can be determined from free oscillation data only if the shear velocity is known very accurately. Once the velocity structure is well known free oscillation data can be used to modify the average density of the upper mantle. The mass and moment of inertia are then the main constraints on how the mass must be redistributed in the lower mantle and core.
Dispersion of Rayleigh waves for purely oceanic paths in the Pacific
Authors: Piermattei Rodolfo , Nowroozi Ali A. 
Published: July 2021

abstract
Thirty-five shallow, distant earthquakes located in the Pacific and recorded at the Ocean Bottom Geophysical station OBS III by a long-period vertical seismograph and a long-period crystal hydrophone were selected for analysis of the dispersion of Rayleigh waves. The sensors are part of the Lamont Geological Observatory's instrument package implanted in May 1966 approximately 200 km west of San Francisco at a water depth of 3.9 km. The location of the station and that of the epicenters, all in the ocean, give us for the first time the oppurtunity of studying purely oceanic paths. The group velocity dispersion curves in the period range 12-40 sec show minor regional differences in the oceanic crustal structure. For the comparison, dispersion curves were obtained for 24 of these earthquakes from the seismographs recorded at the Berkeley seismograph station, BKS. Most of the pairs of dispersion curves show no significant differences due to crossing the continental margin. However, the group velocities of Rayleigh waves from southern Alaska and Easter Island are higher at OBS III than at Berkeley by as much as 0.1 km/sec. Realizing that theoretical models based exclusively on surface-wave data are not unique, and taking Dorman's oceanic model 8099 as our starting point, we were able to fit our experimental dispersion curves using models characterized by a low-velocity zone starting at a depth of about 60 km. According to this type of solution the crust is thicker along the paths from south Alaska and Easter Island, parallel to the coast, than along the other paths examined. The pressure-to-displacement ratio (P/D) is not very sensitive to changes in the models for periods greater than 12 sec. It is, however, useful in determining the local sedimentary structure from short-period waves.
Analysis of seismic peak amplitudes from underground nuclear explosions
Authors: Murphy J. R. , Lahoud J. A. 
Published: July 2021

abstract
Ground-motion data recorded from 99 underground nuclear event ranging in yield from about 1 to 1200 kilotons are analyzed. The data were measured at more than 500 different stations with the source-to-station distance ranging from less than 1 to approximately 600 kilometers. More than 2,900 acceleration, displacement and velocity peak resultant vector data points are included in the analysis. A comparison of the results of the statistical analysis with expected results using cube-root of yield scaling concepts, shows that the peak amplitude of displacement cube-root scales whereas peak acceleration and velocity do not cube-root scale. Relative differences in the yield and distance exponents, n and m, obtained from the statistical analysis, are explained in terms of differences in the frequency content of recorded ground motions.
The observed peak amplitude measurements from the events Boxcar and Benham are compared with predictions based on the statistical analyses.