bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects on structures of the Managua earthquake of December 23, 1972
Authors: Wyllie Loring A. , Wright Richard N. , Sozen Mete A. , Degenkolb Henry J. , Steinbrugge Karl V. , Kramer Samuel 
Published: September 2021

Abstract
The December 23, 1972, earthquake in Managua, Nicaragua caused extensive damage to structures throughout the city of Managua. There was damage to virtually every building in Managua, a city of approximately 400,000 inhabitants. An estimated 10,000 people were killed, mostly in the collapse of homes built of native taquezal construction. The city contained numerous reinforced concrete structures designed to recent standards. Although many of these buildings were heavily damaged, with some collapses, some had only minor damage. There were also several structures of structural steel.
The paper provides an overview of structural effects and discusses the performance of selected buildings in Managua illustrating the range of performance of modern construction. Damage to numerous other buildings will be discussed. The paper, while emphasizing the structural effects on buildings, also discusses the performance of non-structural elements, mechanical equipment, etc.
Rayleigh waves in a half-space with bounded variation in density and rigidity
Authors: Rao C. R. A. 
Published: September 2021

abstract
The stress equations of motion of elasticity are solved by the power series method for an inhomogeneous, isotropic elastic semi-space whose rigidity modulus μ and density ρ are defined by ρ = μ ∞ + ( μ 0 − μ ∞ ) exp ( − ε x 2 ) , ρ = ρ ∞ + ( ρ 0 − ρ ∞ ) exp ( − ε x 2 ) , ε &gt; 0 , x 2 ∈ [ 0 , ∞ ]. The period equation for Rayleigh waves is derived and discussed numerically. The solutions may also be useful for body-wave studies.
Source mechanisms of microearthquakes associated with underground mines in eastern Utah
Authors: Smith Robert B. , Winkler Patrick L. , Anderson John G. , Scholz Christopher H. 
Published: September 2021

abstract
A detailed microearthquake survey, with acoustic monitoring, was conducted in the Sunnyside coal mining district of eastern Utah to investigate the possible relationship between earthquakes and mining. Acoustic emissions from events of magnitude less than −1 showed an average rate of 180/hr and decreased following the latest mining activity. These small events appear to have originated as shear failures near the mine walls. Rates of earthquake activity averaged hundreds per day with magnitudes from −0.5 to +2.8. The zone of greatest seismic activity was located 1 km beneath a portion of the mine which exhibited floor and roof failures. A composite fault-plane solution defines reverse faulting with nodal planes striking N15°E. The P axis strikes S75°E and dips 25°W, and the T axis strikes N75°W and dips 65°E. These directions are in general agreement with the stress pattern attributed to the tectonic development of the nearby San Rafael swell and suggests the possibility that the main earthquake energy may be derived from regional tectonic stress. Spectral analyses of direct shear waves from the submine earthquakes yielded estimates of source parameters at hypocentral distances from 1.3 to 3.0 km for events of magnitude +1.2 to +2.8. Stress drops range from 0.2 bar for a moment of 2.4 × 1017 dyne-cm to 9.6 bar for a moment of 63 × 1017 dyne-cm with corner frequencies from 10 to 14 Hz. These data document the range of measured source spectra to hypocentral distances less than 2 km.
Relation between P- and S-wave corner frequencies in the seismic spectrum
Authors: Savage J. C. 
Published: September 2021

abstract
A comprehensive set of body-wave spectra has been calculated for the Haskell fault model generalized to a circular fault surface. These spectra are used to show that in practice the P-wave corner frequency (ƒp) may exceed the S-wave corner frequency (ƒs) when near-sonic or transonic rupture propagation obtains. The explanation appears to be that in such cases ƒs is so large that it is not identified within the recorded band, but rather a secondary corner is mistaken for ƒs. As a consequence of failing to detect the true asymptotic trend, the high-frequency falloff of the spectrum with frequency is substantially less for S waves than for P waves. This explanation appears to be consistent with the demonstration by Molnar, Tucker, and Brune (1973) that ƒp may exceed ƒs.
Trend enhancement of seismic data as a guide to structural interpretation
Authors: Stewart Ian C. F. 
Published: September 2021

abstract
The main zones of seismic energy release in South Australia probably correspond to major basement fractures. A method is given here to extract the energy release trends from seismicity maps, in order to outline subsurface lineaments more accurately. The techniques are similar to those employed in image processing. Tectonic structure may be revealed which is not readily apparent from epicenter plots or other geophysical data.
Low-rise building damage from low-amplitude ground motions
Authors: Scholl Roger E. 
Published: September 2021

abstract
Data on offsite low-rise building damage from underground nuclear testing at the U.S. Atomic Energy Commission's Nevada Test Site are available for seven large tests in the period from 1966 to 1970. The data, while sparse, provide an adequate sample for the investigation of motion-damage relationships. Damage in the study is statistically described in terms of the incidence of damage complaints, the incidence of buildings damaged, and damage cost. Using 5 per centdamped response-spectrum acceleration amplitude to characterize ground motion, the plotted data fit reasonably well with previous motion-damage relationships established from extensive data available from the 1969 RULISON underground nuclear explosion experiment conducted in western Colorado.
Seismic response for self-strained structures
Authors: Paz Mario , Cassaro Michael A. , Stewart Steven N. 
Published: September 2021

abstract
The seismic response of multistory building and other structural systems is affected by the existence of self strains which may be induced by temperature gradients, mechanical actions, or prestraining. The fundamental dynamic properties such as natural frequencies and mode shapes are influenced by the presence of these strains. As a consequence, the response of the structure changes to the extent that the self strains change its dynamic characteristics and to the extent that these characteristics are relevant in the interaction of a particular structure with a given ground motion.
This paper presents a detailed study of some simple structures such as beams and frames whose members are subjected to initial strains. The homogeneous differential equations of motion are expressed in terms of the stiffness, mass, and geometry matrices and a parameter accounting for the self-strain effect. The solution of the resulting eigenvalue problem is used to write the modal equations into which the desired ground motion is applied.
The final response is obtained from the appropriate shock spectrum and the application of root-mean-square superposition technique. The disturbing action produced by the ground motion of the well known El Centro earthquake of 1940 is applied to several structures in which the amount of self-strain is varied as a parameter.
Crustal structure in the Gangetic Plains of the Indian sub-continent from body waves
Authors: Dube R. K. , Bhayana J. C. 
Published: September 2021

abstract
Crustal structure in the Gangetic Plains of India has been investigated using body-wave data of earthquakes. A three-layered crust has been interpreted, consisting of a top layer of 2.7-km/sec P-wave velocity and 3.7-km thickness, an intermediate layer of 5.64-km/sec velocity and 15.2-km thickness and a bottom layer of 6.49-km/sec velocity and 21.4-km thickness. The average depth of the M discontinuity obtained is 40.3 km. The shear-wave velocities for the Sg, S*, Sn phases are 3.45, 3.85 and 4.61 km/sec, respectively. The velocities of both P and S waves are lower than those obtained for the Peninsular Shield of India.
Variation of source properties: The Inangahua, New Zealand, aftershocks of 1968
Authors: Gibowicz S. J. 
Published: September 2021

abstract
A theoretical relationship between seismic moment and local magnitude ML is derived from the relationship between magnitude ML and source dimension given by Randall (1973). For a circular fault of radius smaller than about 0.5 km, the magnitude ML is proportional to the logarithm of the seismic moment Mo, and these values alone cannot specify other source parameters. For greater radii the values of Mo and ML define Brune's (1970) far-field spectrum and in these cases other source characteristics can be readily obtained. The seismic moment can be estimated from the long-period amplitudes, and therefore the moment-magnitude relation provides a convenient method for determination of the source properties.
The relationship between the logarithm of the various source parameters and seismic moment is considered for a number of regions and earthquake sequences. It appears to be of linear form and, furthermore, it seems that the same slope coefficient can be used in different regions. Source properties show regional differences, and the most suitable parameter to describe these differences is the average displacement.
Besides the regional variations, there seems to be a time variation of source properties. This is the case for the Inangahua aftershock sequence, during which the variation of the displacement residuals correlates with the variation of the coefficient b, which defines the frequency-magnitude relation.
An application of a stochastic model to a volcanic earthquake swarm
Authors: Filson John , Simkin Tom 
Published: September 2021

abstract
The Kolomogorov model of event occurrence as developed by Knopoff in earthquake model studies has been applied to a volcanic earthquake swarm. It is shown that in this case, where the rate of seismic energy release was nearly constant in time, the model adequately relates the various seismicity statistics of the swarm.
The Mt. Rainier earthquake of July 18, 1973, and its tectonic significance
Authors: Crosson Robert S. , Frank David 
Published: September 2021

abstract
On July 18, 1973, a magnitude 3.9 earthquake was strongly felt at Longmire and surrounding areas near Mt. Rainier, Washington. Network analysis permitted an accurate hypocenter to be located at 46°49.29′N and 121°49.86′W at a depth of 10.9 km, about 7 km southwest of the summit of Mt. Rainier. No prolonged aftershock sequence was generated, although two small aftershocks were recorded and located. Aerial photographs of the epicentral region reveal several northwest-trending lineaments which may be related to active faults in the region, although no surface ground breakage was discovered. The focal mechanism obtained for the main shock is well constrained and consistent with right-lateral strike-slip motion along a northwest-trending fracture, in general agreement with northwest-trending surface lineaments. The nature of the relationship of the earthquake occurrence to Mt. Rainier is uncertain. The principal compressive axis direction is in agreement with that found in the central Puget Sound basin. However, the shallow depths, the strike-slip mode of faulting, and the past evidence of earthquakes near Mt. Rainier suggest a direct relationship between faulting, earthquake generation, and the volcano location.
Rayleigh- and Love-wave dispersion up to 140-second-period range in the Indonesia-Philippine region
Authors: Gupta Harsh K. , Hamada Kazuo 
Published: September 2021

abstractGroup velocities for Rayleigh waves extending to 140-sec-period range have been determined for 10 paths in the Indonesia-Philippine region using moving window analysis. The group velocities for five of these paths have been determined from the vertical as well as the longitudinal components and the values obtained from the two components tally with each other. It has also been possible to obtain Love-wave group velocities for three of these paths. On the basis of group-velocity values and regions covered, the observed Rayleigh-wave group-velocity data could be divided into three groups. The first group includes data for paths mostly confined to deep ocean and the observed data could be explained by standard oceanic models such as 8099. The second group includes data for paths lying partially within seismically active regions and models ARC-1 and ALRDG-9 fit with these data. The third group shows still lower group velocities for paths entirely confined to seismically active regions. The shear velocities inferred from Love-wave dispersion data are higher than those inferred from Rayleigh-wave data. In general, the group velocities varied greatly within small distances even in the longer period range, indicating strong lateral heterogeneities in the mantle.
Relation of geological structure to seismicity at Pahute Mesa, Nevada Test Site
Authors: McKeown F. A. 
Published: September 2021

abstract
Some of the abundant and unique geological and seismological data acquired at the Nevada Test Site is integrated with the objectives of (1) resolving some of the ambiguity in explanations of the source of aftershocks of nuclear explosions, and (2) demonstrating the value of using detailed geological and seismological data to infer realistic source parameters of earthquakes.
The distribution of epicenters of aftershocks from nuclear explosions at Pahute Mesa suggests that they are related to faults or intersections of faults in the buried ring-fracture zones of calderas rather than to the conspicuous basin-and-range faults exposed at the surface. Histograms of fault length show clearly that faults in a basin-and-range regime differ significantly in length, median length, and distribution of length from faults in a caldera regime. A histogram of fault lengths derived from magnitudes of aftershocks shows both the median and distribution charactersitics of caldera faults rather than of basin-and-range faults. Cumulative frequency-fault length-squared plots also show differences in the two fault regimes, and have slopes, herein called bf slopes, of −0.89 and −1.08 for caldera and basin-and-range faults, respectively. The bf slopes are similar to the average slope of a cumulative frequency-strain plot for aftershocks rather than to the b slopes for cumulative frequency-magnitude plots. Although the significance of b and bf slopes and differences between them are not resolved clearly, it is concluded that the fault length and strain data reflect dimensions of seismic sources rather than energy of seismic events.
The principal conclusion of the investigation is that the most obvious geology of a seismically active area may not provide the proper basis for inferring seismicsource parameters.
A note on the duration of earthquake and nuclear-explosion ground motions
Authors: Hays Walter W. 
Published: September 2021

Abstract
The duration of ground acceleration, an important engineering seismology parameter, was determined for a subset of nuclear explosion and earthquake accelerograms. The nuclear-explosion, ground-motion data sample consisted of accelerograms derived from velocity recordings of high-yield events, MILROW and CANNIKIN, which have been assigned surface-wave magnitudes of 5.3 and 5.7, respectively. The earthquake-data sample consisted primarily of the Richter magnitude 6.6 San Fernando earthquake accelerograms. The criterion used to define duration of ground acceleration was the amount of time that the absolute acceleration is ≧ 5 per cent g, an approximate index of the strong phase of ground shaking. On the basis of this criterion and the data subset used, the duration of earthquake ground acceleration differs from that of nuclear explosions. The difference, which is not as great as has generally been thought in the past, is small inside 20 km. Earthquake durations are greater beyond 20 km. The scatter in the duration data was analyzed and found to be sensitive to local site amplification phenomena. These preliminary conclusions need to be validated by further research.
Focal mechanisms of some recent Himalayan earthquakes and regional plate tectonics
Authors: Tandon A. N. , Srivastava H. N. 
Published: September 2021

Abstract
Focal mechanism solutions of 12 recent earthquakes along the northern boundary of the Indian-Eurasian plates, from Hindukush to Burma, have been determined assuming the double-couple hypothesis. It has been found that the majority of earthquakes are of thrust type with the pressure directions acting at right angles to the faults/mountains, but, for a few of the earthquakes the orientations of the pressure directions are almost along the strike of the faults. Such observations could be partly explained in terms of the concept of “flake tectonics” as proposed for continent-continent collisions. A number of earthquakes in the eastern Himalayas and Burma show normal dip-slip or predominantly strike-slip movements. These anomalies call for further refinements of the plate theory in this zone of complicated deformation.
Three adaptive filters for the detection of body waves, with application to deep seismic soundings
Authors: Souriau Marc , Veinante J. L. 
Published: September 2021

Abstract
This paper deals with the sequential adaptive filtering of body waves based on a systematic analysis of correlations (covariances) between available digital data of deep seismic soundings. The initial step is to develop a fast algorithm for computing the covariance. We show how a simple recursive filter is well-fitted. First, a deconvolution filter based on the prediction error is developed; for ease in computation, it is derived from a one-point analysis. Second, we use a polarization filter defined by Flinn (1965). Through a theoretical analysis of the seismic field, we show how the filter is biased when it is applied to rectilinear signals in a nonisotropic noise, and we justify an empirical adjustment. Third, an original filter is based on the permanent analysis of space correlations between seismic stations, inside an arbitrary discrete fan of apparent velocities. Applied to three contiguous tracks with arbitrary spacings, the filter is able to enhance any phenomenon with a variable velocity so long as that velocity is included inside the fan. By spectral analysis, space aliasing and velocity resolution are specified, and capabilities of other procedures are revised. The three filters are applied to the same experimental data in order to estimate their relative efficiency.
Premonitory changes in ts/tp due to anisotropy and migration of hypocenters
Authors: Gupta Indra N. 
Published: September 2021

Abstract
The anisotropic characteristics of stress-induced cracks in dilatant rock can significantly influence the observed values of ts/tp obtained using the Wadati diagram. Systematic vertical migration of hypocenters of foreshocks within a region of thrust tectonics can lead to variations in both ts/tp and orientation of the compressive stress axis of the same type as observed before several thrust-type earthquakes. In this model, the seismic velocities become considerably anisotropic due to preferential alignment of open cracks, but it is not essential to assume pre-earthquake flow of groundwater into the dilated zone. Observations of ts/tp versus depth of focus in the Garm region, USSR and some other results appear to support this possibility.
Return periods for rock acceleration in western Nevada
Authors: Douglas Bruce M. , Ryall Alan 
Published: September 2021

abstract
A method is described for determining expected acceleration return periods, based on calculations involving magnitude, fault length and distance to the causative fault. The method permits earthquake magnitude and duration of strong motion to be associated with these return periods. In addition, because attenuation equations are in terms of distance to the causative fault, instead of focal distance, sites can be considered which are in the immediate vicinity of potential faults. Results of calculations indicate that for an average site in the western Nevada region maximum-amplitude, maximum-duration ground motion has a recurrence time of the order of thousands of years. This result, based on a relatively brief sample of instrumental data, is entirely consistent with geological field data representing time periods two to three orders of magnitude longer. Smaller ground motions have correspondingly smaller return periods, down to about a decade for accelerations greater than 0.1 g, when caused by all earthquakes with magnitude 5 or greater. Our results indicate that evaluation of seismic risk in terms of a single peak ground-motion parameter may lead to risk estimates which are several times too high.
The identification of building structural systems
Authors: Marmarelis P. Z. , Udwadia F. E. 
Published: September 2021

abstractThis paper models a building structure as a nonlinear feedback system and studies the effects of such a system model on the structural response to strong ground shaking. Nonlinear kernels arising in the identification procedure have been investigated and an error analysis presented.Applications of the Weiner method in studying the response of a reinforced concrete structure to strong ground shaking have been illustrated. The nature of the second order kernels has been displayed and the nonlinear contribution to the response at the roof level, during strong ground shaking, has been determined.
Study of seismological evasion
Authors: Evernden Jack F. 
Published: September 2021

abstract
This paper discusses seismological aspects of various proposed means of obscuring or hiding the seismic signatures of explosions from a surveillance network. These so-called evasion schemes are discussed from the points of view of both the evader and the monitor. The analysis will be conducted in terms of the USSR since that country is so vast and its geological and geophysical complexities are so great that the complete spectrum of hypothesized evasion schemes requires discussion.
Part I of this paper was a general discussion of these evasion schemes, placing the concepts within the reality of general factors influencing effective use of the techniques. This part of the paper (part II) describes techniques for quantitative investigation of evasion schemes when the only noise problem is normal microseismic noise, and will give analyses of several seismological networks as regards their capabilities to restrain imagined clandestine testing by the USSR under such noise conditions. Part III will describe techniques appropriate for use when the noise problem is the P- and surface-wave codas of earthquakes, and will give analyses of capabilities of several seismological networks to restrain use of such codas for effective evasion.
Analysis of seismograms from a downhole array in sediments near San Francisco Bay
Authors: Joyner William B. , Warrick Richard E. , Oliver Adolph A. 
Published: September 2021

abstract
A four-level downhole array of three-component instruments was established on the southwest shore of San Francisco Bay to monitor the effect of the sediments on low-amplitude seismic ground motion. The deepest instrument is at a depth of 186 m—2 m below the top of the Franciscan bedrock. Earthquake data from regional distances (29 km ≦ Δ ≦ 485 km) over a wide range of azimuths are compared with the predictions of a simple plane-layered model with material properties independently determined. Spectral ratios between the surface and bedrock, computed for the one horizontal component of motion that was analyzed, agree rather well with the model predictions; the model predicts the frequencies of the first three peaks within 10 per cent in most cases and the height of the peaks within 50 per cent in most cases. Surface time histories computed from the theoretical model predict the time variations of amplitude and frequency content reasonably well, but correlations of individual cycles cannot be made between observed and predicted traces.