bluuebunny/crossref_metadata_2025_split huggingface dataset:
Integrated and frequency-band magnitude, two alternative measures of the size of an earthquake
Authors: Howell B. F. , Lundquist G. M. , Yiu S. K. 
Published: September 2021

Abstract
Integrated magnitude substitutes the r.m.s. average amplitude over a pre-selected interval for the peak amplitude in the conventional body-wave magnitude formula. Frequency-band magnitude uses an equivalent quantity in the frequency domain. Integrated magnitude exhibits less scatter than conventional body-wave magnitude for short-period seismograms. Frequency-band magnitude exhibits less scatter than body-wave magnitude or integrated magnitude for both long- and short-period seismograms. The scatter of frequency-band magnitude is probably due to real azimuthal effects, crustal-transfer-function variations, errors in compensation for seismograph response, microseismic moise and uncertainties in the compensation for attenuation with distance. To observe azimuthal variations clearly, the crustal-transfer functions and seismograph response need to be known more precisely than was the case in this experiment, because these two sources of scatter can be large enough to explain all of the observed variations.
Seismic studies: South central Illinois earthquake of November 9, 1968
Authors: Stauder William , Nuttli Otto W. 
Published: September 2021

Abstract
The largest earthquake to occur in the central Mississippi seismic region this century took place in south central Illinois on November 9, 1968. The hypocenter and origin time based on observations from twelve regional stations varying in epicentral distance from 171 to 549 km, are 37.95°N, 88.48°W, h = 25 km, 0 = 17h01m42.0s ± 0.2s.
Travel times of P at stations distant less than 2600 km indicate regional mantle variations, corresponding to rays bottoming at depths down to 650 km. Beyond this point travel times show a much smaller dependence, if any, on region. For stations in the central United States P times may be fitted by two straight line branches which intersect at about 600 km. The first branch corresponds to Pn, the second to rays refracted from a surface at depth 97 km with a velocity below it of 8.37 km/sec. At larger distances (48°-100°) there are non-azimuth dependent residuals with respect to the Herrin Tables averaging about −1.5 sec, indicating a source-region correction with respect to these tables.
Body wave magnitude was determined to be mb = 5.54 ± 0.44 for stations for which Δ &gt; 25°, and mb = 5.44 ± 0.29, using Evernden's formula, for Pn in eastern North America. Surface waves give a value Ms = 5.2.
The fault plane solution determines two nodal planes each striking approximately north-south and dipping 45° to the east and to the west, respectively. This corresponds to dip slip, reverse motion, and to a horizontal east-west axis of compressional stress. While there are no mapped faults in the immediate epicentral region, the motion indicated is in conformity to that along the Wabash Valley Fault System 10 miles to the east.
Note on an aftershock study, south central Illinois earthquake of November 9, 1968
Authors: Stauder William , Pitt Andrew M. 
Published: September 2021

Abstract
In an effort to monitor aftershock activity following the southern Illinois earthquake of November 9, 1968, a network of ten high gain seismic stations was established in the vicinity of the epicenter of the earthquake. The network began recording on the fourth day after the earthquake and operated for a period of ten days. During this time only one very small aftershock was recorded. The hypocenter of this shock was about 10 km south and at the same depth as that of the main shock.
Permanent stations of the region recorded two other aftershocks within two days of the main shock, and one more three and a half months later. The exceptionally low level of aftershock activity is an anomalous feature of the Southern Illinois-Southeast Missouri seismic zone.
Strong earthquake motion and site conditions: Hollywood
Authors: Duke C. M. , Luco J. E. , Carriveau A. R. , Hradilek P. J. , Lastrico R. , Ostrom D. 
Published: September 2021

abstract
An investigation was made to determine the feasibility of isolating the effects of site conditions on strong earthquake accelerograms. The set of accelerograms recorded simultaneously in 1952 at the roof, in the basement and on the ground outside the 14-story Hollywood Storage Building was chosen for analysis. Fourier spectra were computed for the two horizontal components at each of the three recording places and were used after smoothing to compute the ratios of spectra for adjacent points. Dynamic models of the subsurface conditions, the foundation and the building were established. Certain of the spectral ratios were also determined theoretically.
The primary result is the development of a method of isolating effects of site conditions in Fourier spectra of accelerograms. Good theoretical checks were obtained on soil-structure interaction and structural response in the east-west direction. The absence of bedrock accelerograms prevented the obtaining of a theoretical check on free-field amplification, although plausible bedrock Fourier spectra were obtained. The subsurface model should be useful for further analyses.
The earthquake volume
Authors: Duda Seweryn J. 
Published: September 2021

Abstract
A method is presented enabling one to estimate the volume of seismic events with all possible magnitudes and focal depths. The underlying observational data are either the travel times of body waves, or the equivalent magnitude calibration curves for body waves, if the absorption of body waves is neglected.
The method is applied to the newest P-wave travel times. The distance from the focus to a point at which a given critical strain existed during the event is computed. The volume within strains larger than the critical prevailed during the event is obtained as a function of magnitude and focal depth. The volume so found is in agreement with a previous determination of the earthquake volume as a function of magnitude.
Event identification for test ban control
Authors: Ericsson Ulf A. 
Published: September 2021

Abstract
This paper describes a method to determine the usefulness of seismological event identification criteria for underground test ban control with or without on-site inspection. The method rests upon the notion that such control should be deterrent, by confronting a prospective violator with a certain disclosure probability at a politically determined level. Simple decision theory is then applied to the statistical properties of identification measures, to find the required compromise between a sufficient probability to disclose explosions and a not too high incidence of false alarms about earthquakes. A clean separation between the political requirements and the seismological capabilities is obtained. The latter are expressed by identification curves similar to the receiver operating characteristics curves employed in telecommunications analysis. The political requirements appear as geometrical conditions on the identification curves, expressing the required deterrence, the number of yearly explosions and earthquakes to be considered and the permitted number and quality of inspections, in the case of control with inspection. In the case of control without inspection, the acceptable rate of false alarms is included. The method also shows how identification criteria are most efficiently exploited.
Application to some published observations shows identification by short-period body-wave magnitudes and long-period surface-wave magnitudes to be most efficient. It remains, however, to extend the analysis to weak events and low signal-to-noise ratios. For applications the acquisition of proper statistics is essential.
Spectral characteristics of central Nevada microearthquakes
Authors: Douglas Bruce M. , Ryall Alan , Williams Ray 
Published: September 2021

Abstract
Fourier amplitude spectra were computed for 40 central Nevada microearthquakes, selected to consider, independently, effects of azimuth and distance from known sources. Spectra were averaged for groups of events to eliminate peculiarities of individual records and emphasize group characteristics. Spectral characteristics did not behave systematically as a function of azimuth from the recording site to the source, but peak spectral frequency was found to correlate strongly with event magnitude and to some degree also with focal distance. These preliminary results suggest that recordings of small earthquakes and microearthquakes can be used to provide detailed information on the character of seismic signals related to properties of the source and propagation path.
The 1968 Inangahua earthquake: Report of the university of canterbury survey team
Authors: Shepherd R. , Dodd T. A. H. , Sutherland A. J. , Moss P. J. , Carr A. J. , Gordon D. R. , Bryant A. H. 
Published: September 2021

Abstract
Observations are reported on the Inangahua earthquake of May 24 1968. The earthquake (magnitude 7) was felt widely in the South Island of New Zealand. An accelograph recorded a maximum of 0.35 g, 18 miles from Inangahua. There were two fatalities and wide damage.
Synthesis of nonstationary seismic signals
Authors: Beaudet Paul R. 
Published: September 2021

AbstractSynthetic seismograms are a powerful tool which can be used to approximate the complex signature which an inhomogeneous, anisotropic, and imperfectly elastic Earth imparts to seismic waves generated by underground nuclear detonations. The concept and design of a time-varying analog filter for generating synthetic seismograms which approximate real seismograms observed from underground nuclear explosions have been developed. The basic design of this filter exploits a non-stationary characteristic commonly observed on seismograms, the gradual increase of period with time.The parameters of the time-varying analog filter were determined on the basis of the characteristics of the radial component of 50 seismograms recorded from underground nuclear detonations encompassing a wide range of yields (80 to 1000 kt) and distances (50 to 550 km) from the detonation. These parameters determine the time-varying response of the analog filter to a white noise input. The comparison of the spectra of synthetic and real seismograms indicates that the synthetic seismograms generated with the time-varying analog filter are close approximations to real seismograms having equivalent yield and range parameters.
Tectonic stresses in Southern Alaska in relationship to regional seismicity and the new global tectonics
Authors: Gedney Larry 
Published: September 2021

Abstract
Fault plane solutions and a strain release map imply that Southern Alaska performs in the role of a sink area unlike that of more classic trench-arc combinations. A broad, apparently interrelated zone of seismic activity extends from the Aleutian Trench to the base of the Alaska Range. While hypocentral distribution and relative seismicity imply that the entire area is performing as a sink for the North Pacific plate, fault plane solutions at the base of the Alaska Range are inconsistent with this premise. It is suggested that Cook Inlet and the lowlands north of Anchorage may represent an ancient trench.
Accumulation of tectonic strain in California
Authors: Savage J. C. , Burford R. O. 
Published: September 2021

AbstractThe shear-strain accumulation in five tectonically-active areas of California has been calculated from triangulation data supplied by the U. S. Coast and Geodetic Survey. Three of the areas lie along active sections of the San Andreas fault. Near Hollister, no appreciable strain accumulation was detected for the period 1930 to 1962. The movement of the fault blocks there appears to be accommodated by slip on the San Andreas and Calaveras faults. Near Cholame, the only appreciable accumulation of shear strain in the period 1932 to 1962 appears to be associated directly with slip on the San Andreas north of Cholame, slip which probably occurred during the 1934 Parkfield earthquake. Significant strain accumulation was confined to a zone centered on the San Andreas fault and extending 10 km on either side. Some of this strain was released in the 1966 Parkfield earthquake. In Imperial Valley, an average accumulation of γ = 0.4 μstrain per year right-lateral (referred to vertical planes parallel to the Imperial fault) shear strain extends over a zone perhaps 100 km wide centered on the Imperial fault. It appears that this shear pattern may be resolved into two zones of shear, one concentrated near the Imperial fault and the other near the San Andreas fault. No appreciable shear-strain accumulation was detected in the two areas that do not lie on the San Andreas fault—Santa Barbara channel for the period 1880 to 1923 and Owens Valley for the period 1934 to 1956.
Lateral variation of rayleigh-wave dispersion characteristics in Australia
Authors: Gupta Harsh K. , Negi Janardan G. 
Published: September 2021

Abstract
Rayleigh wave dispersion data on Australia by Bolt and Niazi (1964) and Thomas (1969) are examined in detail in the period range of 20 to 40 sec. The dispersion characteristics correspond well to region 7 in Santô's (1965) classification. A further and similar inspection of the African mass, Brazilian shield, Canadian shield etc. reveals that the entire family of shield areas systematically belongs to Santô's regions 6 and/or 7. They are uniformly characterized by the absence of appreciable lateral velocity gradients in clear contrast to corresponding extremely steep gradients for high seismicity areas.
Determining magnitude from Lg
Authors: Baker R. G. 
Published: September 2021

Abstract
In this paper, an empirical method is developed for determining magnitude of seismic events from the amplitude of Lg phases recorded at local to regional distances from the events. The data used were obtained from Long Range Seismic Measurements (LRSM) reports for 78 seismic events associated with explosions conducted the Atomic Energy Commission.
Preliminary investigation showed that magnitudes (M) calculated from Lg recordings had less scatter than body-wave magnitudes (m) reported for the same events and stations. A sixth-degree polynomial was found to give the best fit to log amplitude/period (A/T) values plotted as a function of epicentral distance. Amplitude-distance correction factors (Q) are presented in a chart.
Magnitudes from Lg were compared to the average unified magnitudes from LRSM shot reports. For 60 of 68 events, the standard deviation for M was less than that for m. The M values for all of the events were normalized to magnitude 5.0, and average residuals were found for 69 reporting stations. A plot of the residuals on a map indicates that they represent station corrections rather than azimuthal variations. Apparent station corrections (s) are presented for 23 LRSM stations.
A study of the Earth's crust and upper mantle using travel times and spectrum characteristics of body waves
Authors: Gurbuz B. M. 
Published: September 2021

Abstract
The aim of this paper is to investigate the velocity distribution and structure of the Earth's crust and upper mantle from the close collaboration of theory and experimental results of travel times and spectrum characteristics of body waves. The interpretation was based on 38 seismic records which were obtained from the “Project Early Rise” experiment during July 1966. The results refer to the area bounded by latitudes 49°W and 51°30′ and longitudes 93°W and 98°W. A least-squares analysis of the travel-time data was made and the uncertainties of the slopes, intercept times, and corresponding velocities were determined. The observed wide-angle reflections were used to calculate the root mean square velocities applying the T2 - X2 method. Depth calculations for the velocity discontinuities and seismic depth contour maps were made. A model was constructed, and the validity of the proposed new model was tested by comparing the observed travel times, spectrum-amplitude ratios, and relative phase shifts of body waves with theoretically expected values.
Evidence is given for three discontinuities in the Earth's crust with velocities of 6.11 ± 0.01 km/sec, 6.8 ± 0.08 km/sec, and 7.10 ± 0.04 km/sec at average depths 18 ± 2 km and 25.5 ± 0.9 km. Velocities in the uppermost part of the mantle were determined as 7.90 ± 0.05 km/sec and 8.48 ± 0.05 km/sec with interfaces at the average depths of 34 ± 1 km, and 47 ± 1 km, respectively.
Surface waves in multilayered elastic media. Part II. Higher mode spectra and spectral ratios from point sources in plane layered Earth models
Authors: Harkrider David G. 
Published: September 2021

Abstract
Phase and amplitude spectra of Rayleigh and Love waves are presented for two Earth models, one oceanic and one continental shield. The spectra of the first three Rayleigh modes and the first four Love modes are tabulated for point sources at selected depths. These tables along with computer algorithms described here allow one to estimate the amplitude spectra at nontabulated source depths.
The use of spectral ratios as a means of determining source depth is investigated. A source depth of 20 km is obtained for the Fallon earthquake of July 20 1962. This depth agrees with previous estimates but the technique requires a fault-plane orientation which differs from radiation pattern solutions.
Soil strain near a nuclear detonation
Authors: Olsen C. W. 
Published: September 2021

Abstract
Radial and transverse strain seismometers using 6.1-m Invar rods were installed 457, 914, and 1524 m from ground zero on a nuclear detonation at the Nevada Test Site. The detonation, Hutch, took place in alluvium at a depth of 548 m and gave a body-wave magnitude of 5.4 ± 0.2. Dynamic and quasi-static strain data were recorded along with triaxial accelerations at the 914-m location.
The dynamic data show large strains (2 × 10-3 and considerable shear-wave activity related to the subsurface structure. Decay with range, corrected for the inelastic region, shows dependence of peak amplitudes of about R-3, but influence of the alluvium is present. The quasi-static data show large strain steps (&gt; 10-4) at the two nearer stations and considerable dependence on alluvium depth. The strain decay with time is not consistent with that observed on Benham, and, at 914 m, appears to be a permanent step, similar to that observed on the Jorum event.
The microearthquake activity of Mt. Rainier, Washington
Authors: Unger John D. , Decker Robert W. 
Published: September 2021

Abstract
A network of five high-gain portable seismographs was operated around Mt. Rainier, Washington, from July 13 to August 11 1968, to study microearthquakes associated with this volcano. Approximately 345 microearthquakes were detected during the 30-day recording interval. Of these, hypocenters and magnitudes were determined for 65 selected events. The microearthquakes were concentrated in two general regions: (1) about 80 per cent were in a roughly concentric pattern around the western side of the volcano at depths ranging from 0.5 to 15 km, and (2) about 8 per cent were beneath the summit crater at depths ranging from 0.2 to 20 km. About 75 per cent of the microearthquakes were at depths less than 5 km. These two groups of microearthquakes can be further defined genetically, as the first may be teatonic earthquakes not related directly to volcanic processes and the second appear to be earthquakes possibly of volcanic origin. The cumulative frequency versus magnitude relation for the tectionic microearthquakes is
log ⁡ N = 5.2 − 0.82 ( 8 − M ) .
Analyses of earthquake ground motions at Japanese sites
Authors: Kiefer F. W. , Seed H. Bolton , Idriss I. M. 
Published: September 2021

Abstract
Ground motions at several Japanese sites are evaluated using recently-developed techniques which involve assessing the base-rock motion at the site due to an earthquake, establishing the properties of the overlying soil layers, and computing the response at the ground surface using a lumped-mass-analysis procedure. The maximum acceleration and the form of the response spectra for ground motions recorded at the several sites agree reasonably well with the computed values. It is concluded that where the soil conditions can be reliably determined, the analytical procedures offer good promise as a means of considering the effects of local soil conditions in the prediction of ground response.
Oceanic mantle phases recorded on hydrophones in the Northwestern Pacific at distances between 9° and 40°
Authors: Walker Daniel A. , Sutton George H. 
Published: September 2021

abstract
Compressional- and shear-wave arrivals recorded on hydrophones at Midway, Wake, and Eniwetok from 85 earthquakes occurring along the circum-Pacific arc extending from the Aleutian Islands through the Solomon Islands indicate significant differences in the velocity structure in the mantle beneath the deep Northwestern Pacific Basin and the shallower East Caroline Basin-Ontong Java Plateau-Nauru Sea area. For paths in the Northwestern Pacific mantle, travel times of apparent first arrivals are less than Jeffreys-Bullen (J-B) P and S times for distances out to 20° and are increasingly greater than J-B times for distances between 20° and 33°. At distances greater than 33°, P arrivals agree well with J-B times and S arrivals are absent. Out to 30°, compressional and shear travel times fit straight lines of 8.28 ± 0.03 and 4.79 ± 0.04 km/sec, respectively. For the shallower area to the south, compressional travel times are close to J-B times for P out to 18° and are greater than J-B times for distances between 18° and 22°. At distances greater than 22°, P arrivals agree well with J-B times. Out to 24°, the compressional travel times fit a straight line of 8.47 ± 0.48 km/sec. For this area S arrivals are unclear or not apparent.
A microearthquake survey in Kenya
Authors: Molnar Peter , Aggarwal Yash Pal 
Published: September 2021

abstract
A microearthquake survey was conducted in Kenya from December 1969 to March 1970. The recorded activity was confined to the rift system, and, in the main eastern rift, the activity was greatest in the south and decreased northward. Approximate locations of earthquakes showed that activity was not restricted to a central zone in the rift but was scattered throughout it. Depths of focus were shallow—less than 15 km. The most active region was in the Kavirondo rift near the site of a series of earthquakes in March 1968; microearthquakes were concentrated in a very small region approximately 3 to 4 km deep and in a region with dimensions less than 2 km. The locations support the interpretation that these events reflect movement on the Lambwe fault.
Transformation of earthquake displacement field for spherical earth
Authors: Wason Hans R. , Singh Sarva Jit 
Published: September 2021

abstract
An addition theorem for spherical waves is used to transform the displacement field due to an arbitrary shear dislocation in an unbounded homogeneous medium with origin at the focus to that in a coordinate system with origin at the center of the Earth. The final results are expressed in terms of the eigenvector solutions of the vector Naviér equation of dynamical elasticity. Some serious mistakes in recent papers on the subject have been pointed out.