bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surfa ce-wave dispersion computations: Knopoff's method
Authors: Schwab Fred 
Published: September 2021

Abstract
The optimization of Knopoff's method computer computation of surface-wave dispersion, and the comparison of this method with the Thomson-Haskell technic and its extensions are studied. Of the various versions of the Thomson-Haskell formulation for Rayleigh-wave dispersion computations, the reduced-δ-matrix extension is the most powerful, i.e., the fastest which contains the feature controlling the loss-of-precision problem occasionally encountered by the original formulation. It is shown that the results of the δ-matrix extensions are actually contained in Knopoff's work, which appeared earlier than these extensions, and that these results are obtainable directly from his formulation without recourse to δ-matrix theory. The flexibility of Knopoff's method is used to devise a new representation of the Rayleigh-wave dispersion function which is more powerful than the most powerful of the Thomson-Haskell versions, i.e., it contains the loss-of-precision control feature and is about 38 per cent faster than the reduced-δ-matrix extension; in fact, it is about 12 per cent faster than the fastest of the Thomson-Haskell versions. Explicit forms of the new representation are given for the layered-half-space analogs of continental and oceanic models of the Earth, which can be terminated by a homogeneous half-space beginning in the mantle, a liquid outer core, or a solid inner core. The representations for symmetric and antisymmetric modes of the symmetric-plate analog of the Earth are also given. The Rayleigh-wave dispersion functions for the product form of the original Thomson-Haskell formulation, the δ-matrix and reduced-δ-matrix extensions of this formulation, and the representations developed from Knopoff's method, are identical when written out fully. The various technics differ only in their matrix representations of the dispersion function, which, of course, govern the speeds of computation of the various methods.
The Knopoff and Thomson-Haskell technics for computing Love-wave dispersion are compared. Although the matrix representations of the dispersion function differ for the two technics, the functions are identical, except for a possible sign reversal, when written out fully. The speeds of computation are also identical. The representations derived from Knopoff's method are given for the two possible flat-layer analogs of the Earth, which are applicable to Love-wave propagation.
A portable inexpensive seismic system for crustal studies
Authors: Mereu Robert F. , Kovach Ronald J. 
Published: September 2021

Abstract
A portable seismic system designed for use in crustal experiments is discussed in this paper. The main features of the system which make it attractive are (1) a 7-lb commercial stereo tape recorder, (2) a simple chronometer, (3) a capability to be monitored in the field with a speaker rather than with a paper recorder, (4) a timer for self-operation, and (5) low overall power requirements.
The seismic signal from the seismometer is amplified and fed to one channel of the recorder via a voltage-to-frequency converter so that very low-frequency signals can be recorded. Three additional signals made up of a WWVB radio time signal, a 100-Hz oscillator signal (to be used for compensation) and a 10-sec mark from a chronometer are fed into the second channel of the stereo recorder. The total weight of the instrumentation including the seismometer and carrying case is only 51 lb. This system will operate for over 120 hr with 27 lb of 6-volt batteries. This is more than sufficient for most crustal experiments. Because of its lightness and self-operating features, the system can easily be transported to remote areas by light aircraft at a minimum of expense and trouble.
Calculation of surface motions of a layered half-space
Authors: Tsai N. C. , Housner G. W. 
Published: September 2021

Abstract
A new method is presented for computing the transient response of a set of horizontally stratified, linearly elastic layers overlying a uniform half-space and excited by vertically incident, transient plane waves. In addition, a simple approximate method of satisfactory accuracy is developed that reduces the computing time required. Calculated responses are compared with motions recorded under Union Bay in Seattle to evaluate the agreement between recorded and calculated motions.
A high-sensitivity strain/inertial seismograph installation
Authors: Fix James E. , Sherwin John R. 
Published: September 2021

Abstract
A seismograph complex consisting of short-period (SP), long-period (LP), and extended long-period (XLP) inertial and strain seismographs has been installed. Recordings are made on magnetic tape and photographic film. Routine magnifications on the 20-trace, 16-mm film recorders for all three components are: SP inertial, 500 K; LP inertial, 100 K. The noise levels permit equivalent magnifications on the strain seismographs. The complex provides seismic wave discrimination by directional response, which is independent of period, and by detection of differences in phase velocities between P, S, Love, or Rayleigh arrivals. The strain seismographs use 40-m-long rods and moving coil transducers with generator constants of 32,000 v/m/sec. They sense waves of 5 × 10-13 strain at 30 sec and reject the 2 × 10-8 earth-tide strain. A low-noise preamplifier drives a filter assembly which provides SP, LP, and XLP strain outputs. The complex is installed in an abandoned mine 50 km southeast of Phoenix, Arizona. Environmental control is provided by burial at a depth of about 110 m in a quartz diorite, by sealing the mine, and by insulating the seismometers.
Soil behavior and related effects in the Peru earthquake of May 31, 1970
Authors: Enkeboll William 
Published: September 2021

abstract
Soil and water conditions had an effect on the degree of damage to structures. Most structures were located on alluvium with a high water table. Settlements occurred in dike and causeway fill in Chimbote harbor. Severe problems to communication occurred in some areas through embankment failures and road slides.
Performance of school buildings in the Peru earthquake of May 31, 1970
Authors: Meehan John F. 
Published: September 2021

abstract
The paper reports a field investigation of school buildings in the devastated area of this earthquake. Most school buildings did not collapse. Portions of one in Casma and Huaraz collapsed and many were damaged. Had the earthquake occurred in school hours, injury and death would have been high. Specific structural recommendations are made.
Seismic energy transmission to deep-founded structures
Authors: Brown Colin B. 
Published: September 2021

abstract
The predominant seismic energy input into structures is from Rayleigh waves. These attenuate rapidly with distance from the surface and are partially reflected and partially transmitted by a hole in the ground. A structure founded in such a hole may anticipate a smaller seismic input than a surface-founded structure. Estimates of such a reduction are given which indicate that only short buildings and material with low shear-wave velocities will provide the proper conditions for this beneficial effect.
Detection capabilities of the Yellowknife seismic array and regional seismicity
Authors: Anglin F. M. 
Published: September 2021

abstract
Detection statistics from a search of 99 days of Yellowknife Array data have been obtained. The mean 50 and 90 per cent cumulative detection levels are found to be m 3.9 and m 4.2 for the third zone from Yellowknife. Regional variations in the detection levels have been found. The 50 per cent cumulative detection level ranges from m 3.8 for Asia to m 4.3 for the Aleutians. Regional values of the slopes of the recurrence curves for log N versus magnitude have been obtained, the mean slope for the third zone from Yellowknife being −0.99.
Magnitude-frequency relation and deep-focus earthquakes
Authors: Acharya H. 
Published: September 2021

abstract
Investigation of the magnitude-frequency realtion for earthquakes in island arcs has revealed lower values of the slope for deep earthquakes in New Hebrides, Solomon Islands and Japan as compared to the values of the slope for shallow and intermediate earthquakes. A very low value of the slope is revealed for the deep Andean earthquakes. The slope is the same for Tonga-Fiji for all depth ranges.
The displacement fields of inclined faults
Authors: Mansinha L. , Smylie D. E. 
Published: September 2021

abstract
Closed analytical expressions for the displacement fields of inclined, finite strike-slip and dip-slip faults are given. They may be readily used in the numerical computation of displacements, and, by differentiation, strain and stress fields may be derived. The expressions are valid both at the surface and at depth.
The 1970 Gediz earthquake in Western Anatolia, Turkey
Authors: Taşdemiroifelg˘lu Mehmet 
Published: September 2021

abstract
The Gediz earthquake of March 28, 1970 in western Anatolia, Turkey, killed 1,086 people and heavily damaged 12,234 houses. Faults of 61-km length were produced in the Gediz area; in general, they strike north or east and are left-lateral normal faults. Vertical displacement reached 2 m in crystalline rock. Rockfalls and landslides were common, and thermal springs were initiated in some areas. Historic records indicate that the maximum previous intensity in this area was VIII, but the local intensity of this earthquake was about IX. The basement rocks of the area are crystalline schists, but the severest damage occurred in areas of Neogene outcrop.
Motion of a rigid disc in an elastic solid
Authors: Mal A. K. 
Published: September 2021

abstract
A rigid circular disc embedded in an infinite, isotropic elastic solid is assumed to be excited by a normally-incident plane, harmonic compressional wave. The disc is assumed to be either in perfectly welded or perfectly smooth contact with the surrounding solid. In each case, the problem is reduced to the solution of Fredholm integral equations of the second kind. For the case of the welded contact, exact numeral solutions valid at any given frequency are given. Approximate solutions valid at low and high frequencies are obtained for both cases and are compared with the exact solution. The displacement and compliance of the disc as well as other quantities of interest are presented graphically as functions of frequency.
A Venus seismic experiment for the late 1970's
Authors: Derr John S. 
Published: September 2021

abstract
NASA is planning a series of small-payload Venus missions, with launches beginning in 1976, some of which may be suited to small active and passive seismic experiments. Because the Earth and Venus are nearly the same size, one may theorize many parallels in seismic and tectonic activity, and any differences will provide information about the development of the Earth, as well as of Venus. A combined passive and active experiment with two separated short-period, three-component seismometers and one explosive charge may be carried as 3 entry vehicles on one spacecraft. The weight of explosive, however, is limited to about 20 kg. This limits the charge-seismometer separation to 1 or 2 km. Acoustic and radio ranging devices measure the positions of the 3 probes on the surface. Seismic velocities would be obtained for any layering down to about 500-m depth. A velocity transducer peaked at 20 Hz is desired for the active experiment, and would give some indication of the presence of microquakes on Venus, although a 1-sec period would be better for a passive experiment. An average science data rate of 30 bps would be adequate if the record from the active experiment is recorded for slower playback. A lifetime of 24 hr appears feasible. A dual launch of identical payloads landed in widely-separated areas would give a vastly greater return for the passive experiment. Although not unambiguous, the data should provide some information on seismic velocities, density, and anelasticity. Science and engineering data returned would determine desirability and feasibility of subsequent long-lived passive experiments with long-period, high-temperature instruments.
The earthquake sequence near Danville, California, 1970
Authors: Lee W. H. K. , Eaton M. S. , Brabb E. E. 
Published: September 2021

abstract
Several thousand small earthquakes, with magnitudes ranging up to 4, occurred near Danville, California, during May, June, and July 1970. Seven temporary seismographs were installed near the epicentral region to augment an existing telemetered network within 1 day after the first felt earthquake. The dense concentration of 10 seismographs within 12 km of the seismic activity and the existence of a reversed seismic-refraction profile through the region permitted a very detailed study of this earthquake sequence. Over 400 events with magnitude greater than 0.5 were located with an average accuracy of ±1 km. The main earthquake region was approximately spherical: 1 km in radius, 6 km deep, and centered about 5 km southeast of Danville, 40 km east of San Francisco. Fault-plane solutions indicate that faulting associated with the earthquakes was of the right-lateral strike-slip type, with a strike of N 35°W.
The earthquakes cannot readily be related to any previously identified geological structure or fault. They suggest that active right-lateral faulting is not restricted to the mapped fault trace of the Calaveras fault. This result implies that not all of the sources of future earthquakes in the San Francisco Bay region can be indentified by surface mapping alone. The use of small earthquakes to map active faulting at depth may help to identify areas of potential earthquake hazards.
Anomalous microtilt preceding a local earthquake
Authors: Wood M. D. , Allen R. V. 
Published: September 2021

abstract
The three largest earthquakes to occur within 50 km of San Francisco during 1970 were centered near the community of Danville, California, and spanned a time interval of 50 sec starting on June 12, at 0330 hr GMT. These earthquakes were greater than magnitude 4.0 and were part of a shallow, tightly-clustered earthquake swarm that persisted for approximately 2 months starting in mid-May 1970. During the same period of time, continuous tilt at tidal sensitivity (10−8 radian) was being recorded in two vaults at distances of 25 and 45 km west of the epicentral area. Two types of anomalous tilting preceded the principal events: (1) a long-term (1-month) constant tilt rate of 8 × 10−10 radian/hr that was recorded by both tilt stations and (2) a short-term (1-day) accelerated micro-tilt change which occurred just prior to the events and was most pronounced on the station closest to the epicentral area. Neither type of anomaly was recognized in the post-Danville record. The lack of a strong correlation with meteorological phenomena to account for the long-term coherency between two tilt stations of 25-km separation and the apparent azimuthal correlation of the Berkeley residual tilt vector with the earthquake epicenters suggests that the anomalous tilt preceding the Danville events were tectonic.
The Broach earthquake of March 23, 1970
Authors: Gupta Harsh K. , Mohan Indra , Narain Hari 
Published: September 2021

Abstract
The recent seismicity of the Broach region has been studied and correlated with the regional geological structure. The macroseismic effects are briefly described. Analysis of the first motion of P-wave data indicates the plane striking N 92°E to be the fault plane as supported by field observations also. The present seismic activity is found to be similar to the recent Godavari Valley earthquake sequence of April 1970 and different from the earthquakes in the Koyna region on the basis of b values, foreshock-aftershock pattern, and the ratio of the largest aftershock to the main shock magnitude.
Structural response results during July 29, 1970 earthquake in Burma-India border region
Authors: Agrawal P. N. 
Published: September 2021

Abstract
The data from the Structural Response Recorder installations during the July 29, 1970 earthquake in the Burma-India border region have been interpreted in terms of structural response results. These results suggest the possibility of dependence of the nature of the response spectrum curves on the azimuth of recording.
The strike of the fault plane, determined on the basis of the directions of the maximum recorded amplitudes, coincides with the local structural trend and is in conformity with the fault-plane solutions for some previous earthquakes in the region.
Array detection and location of core shadow events
Authors: Datt Ram , Varghese T. G. 
Published: September 2021

Abstract
The spectral features and slowness vector of the PKIKP and PP signals recorded clearly at the Gauribidanur Seismic Array (GBA) from four underground explosions (mb = 5.6, 5.9, 6.2 and 6.6) at the Nevada Test Site (NTS) were studied in detail. From the spectral similarity which characterizes their phase-summed signals, in the band 0.5 cps to 1.5 cps, it has been possible to synthesize reference signals, corresponding to these phases. By “chirping” these signals against the appropriately-phased array beams, the onset of these phases were identified for such events down to mb = 5.3.
Application of techniques of velocity and frequency filtering to the GBA records corresponding to 16 well-recorded NTS events (Δ ∼ 127.7° and the San Fernando earthquake of February 9, 1971 Δ ∼ 129.9°) has failed to reveal any precursor to the principal PKP phase which corresponds to the DF branch (PKIKP) of the Bolt (1968) curve. It is found that only the PP phase shows significant spectral differences between the earthquake and the set of explosions investigated.
Characteristic periods of fundamental and overtone oscillations of the earth following a deep-focus earthquake
Authors: Nowroozi A. A. 
Published: September 2021

AbstractThe deep-focus earthquake of July 31, 1970, (1.5°S, 72.6°W, h = 651 km, Mb = 7.1) excited a set of fundamental and overtone free oscillations. From analysis of seismograms recorded at Berkeley, California, at an ocean-bottom station in the Pacific, and at Ogdensburg, New Jersey, the fundamental spheroidal oscillations, l = 10-98, and a number of overtones with n = 1, 2, and 3, fundamental torsional oscillations, l = 3-70, and overtones with n = 1, 2, 3, and 4, are identified. The majority of resolved spectral peaks are above the 95 per cent confidence level. For some modes with periods less than 300 sec, the observed period at each station differs by up to 2 sec. This path-dependency of the period may thus suggest the existence of lateral heterogeneity in the upper mantle. The observed periods are compared to calculated periods for Haddon-Bullen's model HB1 and Derr's model DI-11; for fundamental modes the agreements are good, while differences up to 2 sec exist for some overtone modes. A relationship between order of oscillations, l, the frequency, nωl, and the ray parameter dt/dθ is derived, which is equivalent to the Jean's equation for phase velocity. The relationship implies that each mode with period nTl will travel with phase velocity dΔ/dt along its own ray with parameter dt/dθ. Other models will travel along the same ray if they have the same ray parameter.
The effect of a dipping layer on P-wave transmission
Authors: Rogers Albert M. , Kisslinger Carl 
Published: September 2021

Abstract
A ray-theory development of the effect of dip on P-wave transmission through a single layer over a half-space permits an assessment of errors due to dip in estimates of crustal thickness from observed P-wave spectral properties using transmission coefficients for a nondipping interface. The possibility of simultaneously deriving depth and dip from such observation is also shown. The theory has been tested by experiments in a two-dimensional laboratory model and applied to observations of deep South American earthquakes at small epicentral distances.
Theory and laboratory results show that errors in depth reflecting dip are less than 5 per cent for dips up to 25°. Dip can be estimated by matching observed and theoretical curves, once a velocity contrast has been fixed independently. A curve-matching technique for objectively selecting the best match has been developed.
A variation of parameter study shows that changes in velocity contrast do not change the shape of the crustal transfer function, but peak-to-trough differences increase with increasing velocity contrast. A change in depth of a dipping layer produces no change in the crustal transfer function plotted in dimensionless frequency. The transfer function changes with dip more rapidly for waves incident downdip. If the data window is long enough to include P and PPP (three P legs in the layer), the depth determination is not sensitive to window length, but dip determination is not possible for short windows.
The data for Antofagasta permit one of two solutions, a crust either 46.1 or 56.7 km thick, with the M discontinuity dipping 5° east, with the 46.1 km thickness preferred. This result agrees well with refraction results of others. A less firm result for Naña is a crust 74.7 km thick, with dip 15° to the southeast.
Array studies of seismic waves arriving between P and PP in the distance range 90° to 115°
Authors: Wright C. 
Published: September 2021

Abstract
Arrival times, slownesses and azimuths for coherent signals arriving between P and 60 secafter PP have been measured for 12 earthquakes recorded at the Yellowknife array at distances between 90° and 115°. The slowness (dT/dΔ) and azimuth values for P indicate that corrections to dT/dΔ for local structure beneath the array are small and can be neglected. A statistical study of arrivals from 10 events at distances less than 103° did not demonstrate conclusively the existence of PdP waves, and revealed a pattern of slowness values for precursors to PP similar to that observed by Wright and Muirhead (1969) at a distance of 106.0°. Further, a more detailed examination of three events at distances of 93.1°, 105.5° and 114.5° showed the presence of precursors with slowness values of about 10 sec/deg. These results required the development of an asymmetric reflection hypothesis in which the large amplitudes of these waves are produced by cusps in the travel-time curve near 20° and lateral variations in the uppermost regions of the Earth.
A note on correction of strong-motion accelerograms for instrument response
Authors: Trifunac M. D. 
Published: September 2021

Abstract
Two methods for accelerometer instrument correction are described: (1) a direct numerical differentiation of recorded accelerograms from which high-frequency digitization errors have been filtered out and (2) an ideal “mathematical accelerometer” with a natural frequency significantly higher than the natural frequency of the recording instrument. Although both methods give good results, the first one is recommended for standard use.
Lateral structure-foundation interaction of structures with base masses
Authors: Scavuzzo R. J. , Raftopoulos D. D. , Bailey J. L. 
Published: September 2021

abstract
The interaction of lateral inertia forces of an N-mass structure with a base mass and lateral seismic motion of the foundation is formulated as an integral equation of the Volterra type. Flexibility of the foundation is based on the transient solution of a two-dimensional elastic half-space. Interaction effects are evaluated by comparing the response spectra of the free-field motion to that of the foundation motion. Results show that changes in the response spectra are significant for heavy, stiff structures such as a reactor-containment vessel.