bluuebunny/crossref_metadata_2025_split huggingface dataset:
The tectonic stress and tectonic motion direction in Europe and Western Asia as calculated from earthquake fault plane solutions
Authors: Scheidegger A. E. 
Published: July 2021

Abstract
The statistics of fault plane solutions of earthquakes is further analyzed and it is shown that, to find a best axis or best plane to a set of axes, the eigenvectors of a certain matrix must be calculated. The justification for this procedure follows from the same argument as that of Fisher who showed that the best of a series of directions is obtained by forming the vector sum. The eigenvector technique is then applied to the pertinent axes of fault plane solutions of earthquakes that occurred in Europe and Western Asia. It is shown that, in this region, the focal mechanisms of the earthquakes tend to orient themselves in such a fashion that the P axes coincide with the principal horizontal stress directions, the latter being normal to the geographically prominent features. The null axes tend to lie in a plane normal to the best fitting P axes. The chief random element enters into the orientation of the T axes. All this is in conformity with the predictions of theory.
Total energy and energy spectral density of elastic wave radiation from propagating faults
Authors: Haskell N. A. 
Published: July 2021

abstract
Starting with a Green's function representation of the solution of the elastic field equations for the case of a prescribed displacement discontinuity on a fault surface, it is shown that a shear fault (relative displacement parallel to the fault plane) is rigorously equivalent to a distribution of double-couple point sources over the fault plane. In the case of a tensile fault (relative displacement normal to the fault plane) the equivalent point source distribution is composed of force dipoles normal to the fault plane with a superimposed purely compressional component. Assuming that the fault break propagates in one direction along the long axis of the fault plane and that the relative displacement at a given point has the form of a ramp time function of finite duration, T, the total radiated P and S wave energies and the total energy spectral densities are evaluated in closed form in terms of the fault plane dimensions, final fault displacement, the time constant T, and the fault propagation velocity. Using fault parameters derived principally from the work of Ben-Menahem and Toksöz on the Kamchatka earthquake of November 4, 1952, the calculated total energy appears to be somewhat low and the calculated energy spectrum appears to be deficient at short periods. It is suggested that these discrepancies are due to over-simplification of the assumed model, and that they may be corrected by (1) assuming a somewhat roughened ramp for the fault displacement time function to correspond to a stick-slip type of motion, and (2) assuming that the short period components of the fault displacement wave are coherent only over distances considerably smaller than the total fault length.
Earth tides as a triggering mechanism for earthquakes
Authors: Knopoff L. 
Published: July 2021

abstractSince earth tides represent the largest short-period oscillatory strains in the earth, a test has been made to see if any correlation exists between the times of occurrence of earthquakes in Southern California and the tidal potential. Two tests have been made, one of them a cross-correlation. On either basis, a statistically significant sample of earthquake events gives a correlation with the tidal potential that is of the same magnitude as a random sample.
The statistics of earthquakes in Southern California
Authors: Knopoff L. 
Published: July 2021

abstract
A statistically significant series of earthquakes in Southern California, 1934-1957, variously filtered to avoid aftershocks and events outside a localized area, has been tested for a Poisson distribution. It has been found that, for any of several methods of filtering, the data do not fit a Poisson distribution and hence a causal connection between weak earthquake events is inferred. The conclusion is in accord with that of Aki for large events.
Travel times from central Pacific nuclear explosions and inferred mantle structure
Authors: Carder Dean S. 
Published: July 2021

AbstractTravel time data, from widely recorded nuclear detonations in the Eniwetok and Bikini atolls of the central Pacific, have been compiled and are presented. Although a number of stations recorded ten or more events from each atoll, the resulting data may be considered as from a single point source, precisely known in time and place. Composite P-wave travel times are presented in a graphical form and, in the distance range from 3 to 102 degrees, are represented as eight near straight-line segments. P-wave speeds in the top of the mantle average about 8.2 km/sec to distances beyond 17 degrees, and a sharp discontinuity at 19.5 degrees is indicated. There is no evidence for or against a low-speed layer in the upper mantle nor for a regional shadow zone. A mantle model consisting of a number of discrete spherical shells has been constructed. A core depth of 2,870 km, 30 km short of the accepted value, is calculated from PcP arrival times at Matsushiro and College, which are 2.5 and 3.5 sec. earlier than are indicated in the Jeffreys-Bullen tables.
Crustal structure in central California in relation to the Sierra Nevada
Authors: Mikumo Takeshi 
Published: July 2021

Abstract
Crustal structure in central California (between the latitudes of 36° and 41°N) including the Sierra Nevada was studied by travel times of Pn waves from Nevada explosions and earthquakes, dispersion of surface waves, and correlation between computed and observed gravity anomalies.
Simple two-dimensional models are presented for the structure, parameters of which are determined by least-squares from Pn observations. Theoretical gravity distributions expected from the crustal models are computed by a two-dimensional technique and compared with Bouguer anomalies. In the preferred model, the overall crustal depths to the Moho-discontinuity beneath the Pacific coast region, the Central Valley and the Sierra Nevada are found to be about 22, 26 and 43 km, respectively, indicating a steep crustal thickening under the high mountain region. The dispersion of group velocities of Rayleigh and Love waves passing across the region was investigated from Nevada and Utah earthquakes; Love waves from the Utah earthquake give evidence in support of the derived structure.
Fault motions at the Baldwin Hills Reservoir site
Authors: Hudson Donald E. , Scott Ronald F. 
Published: July 2021

Abstract
A distinction is made between the damaging potential of rapid fault motions associated with earthquakes and those having a relatively slow creep type motion. Information is given on nonseismic movements that have been occurring on faults passing through the Baldwin Hills Reservoir during the past 10 years. The relationship between those faults and the Inglewood fault system is described, and correlations are presented with local elevation changes, horizontal ground movements, and seismic activity. Comparisons are made with similar slow fault motions occurring at other places in California, and attention is drawn to the potential damaging effects of such movements.
Computation of modal solutions in layered, elastic media at high frequencies
Authors: Dunkin John W. 
Published: July 2021

Abstract
Modal calculations of wave propagation in layered, elastic media exhibit numerical difficulties at high frequencies. This report shows that these difficulties are caused by the computation of squares of exponential terms which, although they cancel numerically, cause a loss of significant figures in the secular function and the components of certain matrix products. A matrix formulation is presented that avoids these difficulties and gives a natural decomposition of the modal solutions into source and receiver parts. The formulation is applied to layered systems containing both fluid and solid layers as well as to systems composed of solid layers alone.
The Pg-Pn method of determining depth of focus with applications to Nevada earthquakes
Authors: Greensfelder Roger W. 
Published: July 2021

Abstract
The Pg-Pn method is theoretically developed, including a complete error analysis, and then applied to some Nevada earthquakes. It is found that, as expected, the method is very sensitive to the crustal model used, and the appearance of large errors in depths of focus calculated for some earthquakes leads to the conclusion of a major discontinuity in crustal thickness (ca. 10 km) north and east of Walker Lake, Nevada. This discontinuity may have its surface expression in the Walker Lane, a major right-lateral shear zone which has been defined on both physiographic and geologic grounds.
A study of apparent angles of emergence at Marathon Ontario from the Lake Superior data
Authors: Mereu R. F. 
Published: July 2021

Abstract
A three component array of Willmore seismometers and a hydrophone were used to record the seismic events at Marathon, Ontario during the Lake Superior crustal experiment of 1963. The first part of each record was digitized and from an analysis of the particle motion diagrams, apparent angles of emergence of the seismic rays were determined. It was found that these angles can be used to distinguish between P2 and Pn waves. When the shot distance was less than 220 km., the first arrivals emerged with an apparent angle of 40-50°. As the shot distance was increased beyond 220 km., the rays emerged with an apparent angle of 51-70°. The apparent velocities of the (40-50) and the 51-70°) rays were 6.6 km/sec and 8.2 km/sec respectively. Further analysis of the results showed that the Moho below Marathon dipped downwards toward the south west with an angle of approximately 4°, indicating that the crust is considerably thicker on the south west side of Marathon than on the north east. A study of the ray azimuths gave some evidence of the presence of lateral inhomogeneities in the crust.
Microearthquake crustal reflections, Socorro, New Mexico
Authors: Sanford A. R. , Long L. T. 
Published: July 2021

Abstract
About 25 per cent of the microearthquakes which originate close to Socorro (S minus P ≦ 2.5 secs) produce seismograms with two sharp arrivals about 2.5 and 5.0 seconds after the direct S-phase arrival. The best interpretation of the time-distance data for these late phases is that they are the SxP and the SxS reflections from a crustal discontinuity at a depth of 18 km. The amplitudes of the reflections, which average 0.21 and 0.32 of the direct S-phase amplitude on vertical-component seismograms, are for greater than theoretical amplitudes found by assuming uniform radiation from the focus and reflection of a plane SV wave from a horizontal discontinuity.
The effect of boundaries on wave propagation in a liquid-filled porous solid: IX. Love waves in a porous internal stratum
Authors: Deresiewicz H. 
Published: July 2021

abstract
The dispersion equation in the second approximation for small porosity is deduced for the problem of transverse waves in a porous layer separating two impermeable elastic half-spaces, and the expression for the dissipation per cycle displayed. It is shown that Love waves can be propagated in a porous layer only with phase velocities smaller than that of body shear waves in either of the half-spaces, whereas in an impermeable layer Love waves may exist having phase velocity equal to that of body shear waves in one of the half-spaces.
Seismicity of Hawaii
Authors: Furumoto Augustine S. 
Published: July 2021

abstractOne aspect of the seismicity of Hawaii is investigated by attempting to answer two questions: (1) the possibility of occurrence of major earthquakes in Hawaii, and (2) the probability of occurrence. The first question was answered when a study of the distribution of intensity of the Hawaiian earthquake of 1868 indicated that the earthquake had a magnitude between 714and734. An answer to the second question was approached by studying the occurrence-magnitude relation log N = A − bM for earthquakes of magnitudes 2.5 to 4.9 during a period of 314 years. Extrapolation from the results suggests that major earthquakes may be expected in Hawaii as often as in other seismically active areas. A study of strain release showed that the pattern in Hawaii is consistent with that worldwide.
Routine location of T-phase sources in the Pacific
Authors: Johnson Rockne H. 
Published: July 2021

abstract
A program for the routine location of T-phase sources in the Pacific is described. Data for this program are supplied principally by the Pacific Missile Range hydrophone network. Arrival times and power levels are read at Honolulu for processing by an IBM 7040 computer. The solution for location and origin time is the least-squares fit to all hydrophone arrivals which are weighted according to their distribution in azimuth and their distance from the T-phase source. The velocities for the program are obtained from algebraic functions of latitude and longitude which are based upon shot calibrations and upon hydrographic measurements. A T-phase strength is computed from readings of peak power level in a manner analogous to earthquake magnitude. Early results for the r.m.s. difference between T-phase source locations and the corresponding earthquake epicenters were 0.6° in the Aleutians and 1.1° in the Kuril Islands.
Difference between aftershocks and foreshocks in the relationship of magnitude to frequency of occurrence for the great Chilean earthquake of 1960
Authors: Suyehiro Shigeji 
Published: July 2021

abstract
When a relatively small perceptible earthquake occurred near a tripartite net of high sensitivity in central Japan, a substantial difference was found between its 25 foreshocks and 173 aftershocks in the relation of frequency of occurrence and magnitude. For that study the coefficient “b” in the magnitude versus frequency equation is 0.35 for the former and 0.76 for the latter.
A similar investigation has been carried out on the great Chilean earthquake of 1960, also accompanied by many foreshocks and aftershocks. Using four sensitive and suitably located U.S.C.G.S. stations, Eureka, Tucson, South Pole, and Byrd, foreshocks and aftershocks were located in addition to those reported by U.S.C.G.S. or B.C.I.S. Forty-five foreshocks and 250 aftershocks were found in a period of 33 hours before and 33 hours after the main shock. The same characteristic found for the Japanese earthquake was also found for the Chilean earthquake; i.e. the foreshocks showed a different picture from the aftershocks for the frequency of occurrence, and an appreciably smaller value seems to be valid for “b” of the foreshocks.
Azimuth and slowness anomalies of seismic waves measured on the central California seismographic array. Part I. Observations
Authors: Otsuka Michio 
Published: July 2021

abstract
Arrays of seismographs are usually considered to be detectors which give enhanced signals from distant earthquakes. They also provide, however, a new way of learning more about the structure of the crust and upper mantle. The deviation of the seismic-wave surface from its expected configuration may be regarded as a consequence of non-homogeneous and anisotropic conditions in the earth.
The operations of the University of California network of telemetry stations in the Coast Ranges of California provides an opportunity to discover the practicality of this approach. The situation of this network near the continental margin gives the study particular interest.
The differences in arrival-times between array elements of coherent peaks or troughs of P and pP phases from 28 teleseisms in the period of 1963-1964 were read from the telemetry records of the central California seismographic array. The direction of approach and velocities of the wave fronts were then determined and compared with the great circle azimuths and with the apparent velocities calculated from the Jeffreys-Bullen tables.
The observed anomalies in direction of approach and apparent velocites are found to be cyclic functions of the direction of the source. The amplitudes of these functions are almost 10 degrees in azimuth anomaly and 1.0 sec/deg in slowness anomaly. Error analyses show that the anomaly functions cannot be attributed to the measurement errors.
The derived anomaly functions provide a powerful means of examining crustal and upper mantle structure under the array and perhaps at the source. Variations between subsets of the array indicate significant differences in structure between portions of the Coast Ranges to the north and to the south of Hollister.
Deformation of railroad tracks by slippage on the Hayward fault in the Niles District of Fremont, California
Authors: Bonilla M. G. 
Published: July 2021

abstract
Slippage (also called creep) on the Hayward fault has produced a right-lateral shift of about 0.7 feet in three sets of railroad tracks that were built 55 and 56 years ago. The average annual rate of 0.15 inch per year is about one-third the average rate of slippage on the San Andreas fault, but the rate has been much greater during short intervals. The zone of acute deformation of the tracks is 20 to 80 feet wide; the tracks are underlain by unconsolidated deposits more than 300 feet thick. Surface faulting at this locality in the 1868, and probably in the 1836, earthquake suggests that the processes of fault rupture and fault slippage can alternate at the same locality.
The determination of seismometer damping
Authors: Morencos Julio 
Published: July 2021

a4bstract
Eaton's method of determining the seismometer damping is extended, in order to make it more easily applicable to any value of period and damping.
The theory of the seismometer response to the release test is developed, showing that, for the application of this method, both release and tapping tests are equivalent.
As a summary of the work, curves are plotted corresponding to the function β = f (τ, Q), where τ is the “reduced time” during which the deflection decreases from its initial value ϕ0 (release test) or first maximum one ϕm (tapping test) to Qϕ0 or Qϕm, respectively, Q, being an arbitrary parameter smaller than unity. The graph contains seven curves, for values of Q from 0.1 to 0.5. The higher values are applicable to cases of large period and damping.
Velocity filtering of seismic core phases
Authors: Hannon W. J. , Kovach R. L. 
Published: July 2021

abstract
Recent studies have proposed complexities in the velocity-depth function for the region surrounding the inner core which require additional branches in the travel time curve for PKP in the epicentral range of 125° to 160°. The proposed PKP arrivals can be separated on the basis of their apparent velocities, which range from 24 km/sec to 100 km/sec. Using the Tonto Forest array in Arizona coupled with adjoining LRSM stations in the western United States, an effective linear array of 400 km in size is attained. Data from several events in the distance range from 130° to 160° recorded on this array have been velocity filtered and show some evidence of two precursors to PKP in the distance range from 135° to 143° and at least one intermediate branch between PKP1 and PKP2 at distances greater than 143°. The results appear to support the velocity solution for the core proposed by Adams and Randall, although more data are required before a conclusive discrimination can be made between competing velocity models.
The San Salvador earthquake of May 3, 1965
Authors: Lomnitz Cinna , Schultz Rudolf 
Published: July 2021

abstract
The San Salvador earthquake of May 3, 1965 was preceded by a local seismic swarm of three months duration. The main shock was destructive in a densely populated area of not more than 15 km in radius; the same general area was damaged in the earthquakes of 1576, 1659, 1798, 1839, 1854, 1873, 1880, 1917, and 1919. Over 120 casualties were reported.
The epicenter has been located on the south rim of the Median Trough, a post-Pliocene structure which accounts for the high seismic and volcanic activity in the region. The observed intensity is attributable to shallow focal depth and to the presence of thick inhomogeneous beds of fluviatile pumice. The tectonic setting and shallow subsurface factors should be recognized in future building codes and zoning regulations.
Seismic parameter φ: Computation at very high pressure from laboratory data
Authors: Anderson Orson L. 
Published: July 2021

abstract
By using the accuracy inherent in ultrasonic velocity measurements taken at pressures less than 10 kb, the seismic parameter φ=vp2−(43)vS2 can be computed at very high pressures. The equation used requires the assumption that the second derivative with respect to pressure of the bulk modulus be negligible at all pressures considered. This assumption is checked by computing the compression (V/V0) in the pressure range by equations of state using the assumption, and comparing the resulting values with measured compression. Illustrations are given for MgO and Al2O3.
Regional strain release characteristics for Indian regions
Authors: Chouhan R. K. S. 
Published: July 2021

abstract
The strain accumulation and release curves for shallow and deep focus earthquakes of Indian origin have been constructed for a span of sixty years, from 1905 to 1964. For shallow focus earthquakes, magnitudes 7.2 and above have been considered; for deep focus shocks, magnitudes 6.7 and above are used. Strain rebound characteristics yield a number of very interesting features; for example, the curve for shallow focus earthquakes shows two linear segments of strain accumulation. Deep focus shocks show a single cycle of strain accumulation. Comparison of these curves with similar curves from other regions given by Benioff are made.
High Rayleigh wave phase velocities for the New Delhi, India-Lahore, Pakistan profile
Authors: Gabriel V. G. , Kuo John T. 
Published: July 2021

Abstract
Phase velocities were determined for the New Delhi-Lahore profile by using data from these two stations and earthquakes located approximately on the great circle path through the stations. The phase velocities were found to be higher than those expected for normal continental structures and somewhat similar to those found by Brune and Dorman (1963) for the Canadian shield. A structural model, based on the phase velocity values of the CANSD model given by Brune and Dorman (1963) and consistent with the local geology, was evaluated and is presented herewith as the INDSD model.
It is postulated that high phase velocity values in the Lahore-New Delhi profile indicate the shield character of the crustal structure along the profile, as an extension of the Indian shield located south and southeast of it.
Preliminary results of an investigation of crustal structure in Southeastern Europe
Authors: Papazachos Basil C. , Comninakis Peter E. , Drakopoulos John C. 
Published: July 2021

Abstract
Travel-time curves for the most prominent phases of the longitudinal and shear waves for epicentral distances between zero and 140 km and between 200 km and 1000 km have been constructed for Southeastern Europe. Both refraction and reflection methods indicate a three-layered crust. The average thickness is approximately 16 km for the top layer, 15 for the middle layer and 11 for the lower layer. The crustal thickness varies from about 47 to 32 km from place to place. The extremely low value 0.21 for Poisson's ratio was found in the top as well as in the middle layer.
The 1962 Kaoiki, Hawaii, earthquake and its aftershocks
Authors: Koyanagi Robert Y. , Krivoy Harold L. , Okamura Arnold T. 
Published: July 2021

Abstract
At 18:27:14.3 on June 27, 1962 an earthquake of moderate intensity occurred near the Kaoiki fault system between the volcanoes Kilauea and Mauna Loa on the Island of Hawaii. It was felt strongly on Hawaii, where it caused minor property damage, and was perceptible as far as Oahu to the north-west.
Intense aftershock activity continued for several weeks; 1540 aftershocks were recorded during the initial 60 hours. A hyperbolic decay in the number of aftershocks with increasing time was evident. The epicentral zone covered about 150 square km and focal depths ranged from 3 to 12 km.