bluuebunny/crossref_metadata_2025 huggingface dataset:
Vínculo intergeneracional, infancia y educación: notas para pensar la función de la escolarización de los niños
Authors: Cárdenas Palermo Yeimy
Published: September 2021

En este artículo de reflexión se analizan algunos sentidos sobre el vínculo intergeneracional y sus implicaciones en los modos de asumir las relaciones niños-adultos, frente a las formas de concebir la infancia, la educación y la escuela, como frutos de las reflexiones derivadas de algunas de las investigaciones desarrolladas, en la última década, en la línea “Infancia, cultura y educación”, adscrita al grupo Educación y Cultura Política de la Universidad Pedagógica Nacional de Colombia. Este artículo problematiza las ideas de individualismo y desescolarización que promueven los discursos contemporáneos acerca del niño, así como los riesgos para el sostenimiento de los sentidos de la escolarización y la escuela, como institución responsable de la producción de la humanidad y de su cuidado, a partir del vínculo entre las viejas y las nuevas generaciones. El texto se desarrolla en tres apartados: en el primero se revisa la categoría de vínculo intergeneracional; en el segundo, los sentidos que adquiere el vínculo intergeneracional como principio constitutivo de la escuela moderna y, en el tercero se expone una discusión acerca de la reconceptualización de la función de la escolarización de los niños en la actualidad, con énfasis en el papel del sujeto-adulto que educa en la escuela: el maestro.
Los saberes oficiales en torno a la violencia política 1955-1976: la normativa educativa y las secuencias didácticas del portal Educ. ar
Authors: Billán Yésica Alejadra
Published: September 2021

Este artículo de investigación se ocupa del tratamiento que la violencia política de la historia reciente argentina adquirió en los saberes escolares orientados a la educación secundaria en Argentina desde la reforma educativa del año 1993 hasta el año 2015. Retomando los aportes de los estudios de la violencia política, en este artículo planteamos un análisis de la normativa educativa y las secuencias didácticas del portal Educ.ar a partir de considerar las denominaciones que están presente en estos saberes, pero también los “vacíos” conceptuales que podemos advertir. Dicho análisis permite reconocer la relevancia que cobra el periodo 1955-1976 de la historia argentina en los saberes escolares e identificar los cruces con la memoria social y la carga moral que atraviesa a estos saberes referidos a años controversiales para la historia argentina.
Evaluating large spontaneous deletions in a bovine cell line selected for bovine viral diarrhea virus resistance -MDBK reads mapping to regions in genome not shared with CRIB cell line v1
Authors: not provided aspen.workman , not provided mike.heaton , A. Webster Dennis , P Harhay Gregory , Smith Tim , M Falkenberg Shollie , F. Carlson Daniel , S Sonstegard Tad , not provided ted.kalbfleisch
Published: September 2021

Bovine viral diarrhea virus (BVDV) entry into bovine cells involves attachment of virions to cellular receptors, internalization, and pH-dependent fusion with endosomal membranes. The primary host receptor for BVDV is CD46; however, the complete set of host factors required for virus entry is unknown. The Madin-Darby bovine kidney (MDBK) cell line is susceptible to BVDV infection, while a derivative cell line (CRIB) is resistant at the level of virus entry. We performed complete genome sequencing of each to identify genomic variation underlying the resistant phenotype with the aim of identifying host factors essential for BVDV entry. Three large compound deletions in the BVDV-resistant CRIB cell line were identified and predicted to disrupt the function or expression of the genesPTPN12,GRID2, andRABGAP1L. However, CRISPR/Cas9 mediated knockout of these genes, individually or in combination, in the parental MDBK cell line did not impact virus entry or replication. Therefore, resistance to BVDV in the CRIB cell line is not due to the apparent spontaneous loss ofPTPN12,GRID2, orRABGAP1Lgene function. Identifying the functional cause of BVDV resistance in the CRIB cell line may require more detailed comparisons of the genomes and epigenomes.
Cloning into pSL2680 CRISPR Plasmid - iGEM IISER Pune 2021 v1
Authors: not provided misaal.bedi
Published: September 2021

This protocol can be used to clone the guide RNA and Homologous Repair Template into the pSL2680 plasmid which was a gift from Himadri Pakrasi (Addgene plasmid # 85581 ; http://n2t.net/addgene:85581 ; RRID:Addgene_85581).
p1 21/09 v1
Authors: not provided testnapoke
Published: September 2021

test
FROM RESEARCH SKILLS TO RESEARCHER’S TRANSVERSAL COMPETENCE
Authors: Zogla Irena
Published: September 2021

Different intellectual traditions imbedded in cultural and education settings and theoretical approaches to the understanding of skills, competencies, and transversal skills bring about many uncertainties in the conceptualization of research skills and competencies; together with the social demands towards the quality of graduates' competencies these draw heavily on the changing process of education, quality of educational provision, and interferes with the quality of the graduates’ achievements. Doctoral students usually face a large number of theoretical sources to analyze and make an appropriate theoretical underpinning of research; they also have to meet the uncertainties, experience incompetence that interferes with the allocated time and quality of investigation. While the shift to competence approach in education is thus more complex than many accounts suggest, it does have major implications for important aspects of studies and educators' work. This article aims to initiate doctoral students' thinking of the cultural background of different intellectual traditions in education and identify the most appropriate theoretical sources for their research. The article does not, however, provide final definitions or completed ideas. Based on the experience of the most popular projects in skills’development and theoretical analysis the published considerations might trigger new problems for doctoral students’ investigation and start their navigation in the enormous pool of literature. The article introduces some approaches to understanding and defining research skills, researcher’s competencies, and researcher’s transversal competencies, their structure, and experiences of measuring.
Pengaruh Ekstrak Kayu Manis (Cinnamomum sp.) dan Pembekuan terhadap Fisiologi Ikan Mas (Cyprinus carpio)
Authors: Suwandi Ruddy , Rizkon Karima Fafa , M Jacoeb Agoes , Nugraha Roni
Published: September 2021

Distribusi ikan hidup pascapanen dapat dilakukan dengan perlakuan awal pemingsanan dengan bahan anestesi untuk mengurangi stres selama proses transportasi. Bahan anestesi yang digunakan dapat berupa bahan alami misalnya kayu manis. Penelitian ini bertujuan menentukan pengaruh pemberian larutan ekstrak kulit kayu manis dalam air terhadap waktu pingsan ikan mas, serta menentukan pengaruh lama pemberian pembekuan terhadap laju sintasan, kadar glukosa darah, kondisi mata, dan insang ikan. Konsentrasi terbaik ekstrak kayu manis adalah 1%, yang menyebabkan ikan pingsan setelah 1,58±0,04 menit. Nilai laju sintasan ikan dengan perlakukan pemingsanan setelah dibekukan mencapai 100% pada semua waktu pembekuan -13 oC. Kejutan 45 menit tanpa pemingsanan menghasilkan nilai 100%, sedangkan pada waktu 60 dan 75 menit menghasilkan nilai 88,89% dan 66,67%. Insang ikan mas yang diberi pembekuan semakin lama dapat menyebabkan terjadinya pendarahan dan kerusakan pada filamen insang. Waktu pembekuan yang semakin lama membuat nilai glukosa darah semakin meningkat.
The relation between felt area and magnitude for central United States earthquakes
Authors: Nuttli Otto W. , Zollweg James E.
Published: September 2021

abstract

Felt areas of earthquakes in the central United States are known to increase sizeably with small increases in magnitude. In order to establish a quantitative relation between magnitude and felt area, 22 recent earthquakes were studied, resulting in the empirical equation

m b = 2.65 + 0.098 f + 0.054 f 2 for f ≦ 6

where ƒ is the logarithm to the base 10 of the felt area in square kilometers. This equation can be used to estimate the magnitude of earthquakes in the central United States for which there are intensity maps but no instrumental data. Furthermore, from the equation one can determine that the limit of perceptibility corresponds to a sustained, hard-rock, vertical-component particle velocity of about 22μ/sec.
Seismicity of the Baffin Bay region
Authors: Qamar Anthony
Published: September 2021

abstract

Twenty-eight earthquakes in the Baffin Bay region have been relocated using the method of Joint Hypocenter Determination. The revised locations indicate two parallel, linear trends, one along the northeast coast of Baffin Island and the other in the western part of Baffin Bay. The seismicity does not appear to be controlled by glacial rebound but may be a remnant of sea-floor spreading which occurred 40 to 60 m.y. ago. Early P arrivals at near seismograph stations (Δ < 20°) can be explained by a high-velocity (8.5 km/sec) upper mantle in the Baffin region.
Geodetic determination of strain at the Nevada Test Site following the Handley event
Authors: Savage J. C. , Kinoshita W. T. , Prescott W. H.
Published: September 2021

abstract

Repeated surveys of a trilateration network (aperture greater than 20 km) centered on ground zero for the HANDLEY event, a nuclear explosion at the Nevada Test Site with yield in excess of 1 megaton, suggest that the explosion induced an east-west extension of the network by more than 50 mm. In the year following the detonation, this deformation reversed such that the final configuration represented a small east-west contraction from the pre-HANDLEY state. In the subsequent 2-year period, only minor deformation was detected. Thus, the overall response of Pahute Mesa may be described as stable. The explosion-induced deformation is thought to be partly due to slip on faults driven by the large-amplitude seismic waves from the explosion. The mechanism of the postshot relaxation is not understood.
Seismic source function for an underground nuclear explosion
Authors: Aki Keiiti , Bouchon Michel , Reasenberg Paul
Published: September 2021

abstract

The reduced displacement potential obtained from close-in observation of seismic displacement during an underground explosion usually takes the form of a step function with or without a small overshoot. Theoretical prediction by shock-wave calculation appears to agree with the close-in data. The step-function source has also been supported by the observations on Rayleigh waves at periods longer than 10 sec. We found, however, some inconsistency between the published data on residual potentials obtained from close-in data and those on seismic moments obtained from long-period Rayleigh waves. It appears that only about 13 of the residual potential is transmitted to the far-field at long periods. This discrepancy is, however, consistent with several observations made on teleseismic signals suggesting an impulse rather than a step as the primary form of the potential function. New observations of the two NTS events at distances 2.6 to 7.8 km using wide dynamic range, wide-band accelerometers, combined with data from the far-field, support a large overshoot 4 to 5 times the residual value. This result accounts for the efficiency of the Ms - mb discriminant between earthquakes and explosions with mb around 4 and greater. The compaction of the source volume by spalling was suggested as a possible mechanism for the large overshoot.
Body waves as normal and leaking modes—leaking modes of Love waves
Authors: Radovich B. J. , De Bremaecker J. Cl.
Published: September 2021

abstract

Dispersion curves of leaking modes of Love waves are computed for a one-layer crust-mantle model. The frequency and wave number are complex, but the group velocity is purely real. Group velocities well below the Airy phase of normal modes are found; waves with group velocities between 1.0 and 3.8 km/sec attenuate the least, but even these decay too much ever to be detected. There are no phase velocities between the velocity of the half-space and that corresponding to the Brewster angle.
Statistical prediction of the occurrence of maximum magnitude earthquakes
Authors: Yegulalp Tuncel M. , Kuo J. T.
Published: September 2021

abstract

This paper intends (a) to improve the early results for statistical prediction of the occurrence of maximum magnitude earthquakes obtained by Yegulalp and Kuo by including all of the seismicity data of both Gutenberg and Richter, and Rothé covering the period 1904 to 1965 and (b) to show the predictability of the regional occurrence of maximum magnitude earthquakes for the period 1953 to 1965 by using the seismicity data for 1904 to 1952.

Of 51 regions, as classified by Gutenberg and Richter for the world, data for 46 have been analyzed and tested for their goodness-of-fit to the theoretical extremal distributions. The parameters of the asymptotic extremal distributions have been estimated by the method of least squares. Results show that the regional occurrence of maximum magnitude earthquakes definitely favors the third type asymptotic distribution over the first type. The existence of a finite upper bound for the third type asymptotic distribution is physically consistent with the fact that the strength of the solid Earth is finite.

Among all of the regions, the curves for the northern and western circum-Pacific belt are generally the highest; those for the eastern circum-Pacific belt are the second highest: those for Eurasia, i.e., the Alpide belt and its adjacent regions, are the third highest; and those for the oceans and stable continental masses are the lowest.

The predictability of the regional occurrence of maximum magnitude earthquakes has been tested by predicting the magnitudes corresponding to the return periods of 2, 3, 5, and 13 years for the period 1953 to 1965 and comparing the corresponding number of exceedances with the observed number of exceedances for these magnitudes. Except for the regions with inadequate data, agreement has been remarkably good for most of the regions: thus, the validity and the usefulness of the present results are established.

Apparently, the two sets of the seismicity data of Gutenberg and Richter (1954) and Richter (1958) and that of Rothé (1972) are statistically stable. On the basis of the present complete data for 1904 to 1965, predicted maximum magnitudes in each of 46 regions for the return periods of 20, 50, and 100 years are given.
Topographic effects on ground motion for incident P waves: A model study
Authors: Rogers A. M. , Katz L. J. , Bennett T. J.
Published: September 2021

abstract

A scale model experiment was conducted to study the effect of topography on ground motion for incident P waves. It was found that amplifications as large as 35 per cent may occur in the time domain for a wide-band input with predominant wavelength equal to the width of the scatterer base. The largest diffracted wave observed was a forward scattered Rayleigh wave with an amplitude of about 55 per cent of the incident motion. Examination of the spectral ratios showed that, for more band-limited input pulses, peak amplifications of the crest motions relative to the base may be as high as 200 per cent. These differences are comparable to, but smaller than, the 400 per cent amplifications observed in field studies conducted by Davis and West (1973). Results of a parameter study indicate topographic effects to be weakly dependent on slope and angle of incidence. However, the effects do change significantly as a function of frequency and position on the scatterer. For receiver positions at depth, scattered body waves were found to be more significant. The radiation lobes of these waves are directed predominantly downward. Qualitative agreement was found between the model results and field results observed on a nearly two-dimensional feature (NASA Mountain near Beatty, Nevada) where underground nuclear explosion ground motions were recorded.
The Managua, Nicaragua, earthquake of December 23, 1972: Location, focal mechanism, and intensity distribution
Authors: Algermissen S. T. , Dewey J. W. , Langer C. J. , Dillinger W. H.
Published: September 2021

abstract

The Managua earthquake occurred at a shallow depth of focus beneath the center of Managua, producing a maximum intensity of MM IX in the center of the city. The epicenter of the main shock is determined to within several kilometers by use of the strong-motion accelerogram recorded at the ESSO refinery. Such accuracy is unprecedented for a large Central American earthquake, and makes the Managua earthquake valuable as a calibration event for minimizing the bias in location of other earthquakes in Nicaragua. The character of the distribution of P-wave residuals and the location of the earthquake well inland from the Benioff zone in Nicaragua suggest that much of the bias in epicenters calculated for earthquakes in the vicinity of Managua is due to station effects rather than source effects. P-wave first-motions are consistent with a left-lateral strike-slip fault as the earthquake source.
Catalog of Nicaraguan earthquakes
Authors: Leeds David J.
Published: September 2021

abstract

A documented catalog of 457 Nicaraguan seismic and volcanic events reported for the 453-year period 1520-1973 is presented. Earthquakes range in size from those that caused the destruction of the former capital at Leon in 1609, 1663 and again in 1885 to instrumentally recorded events of small magnitude. The present capital, Managua, was devastated in 1931 and in 1972. Magnitude ranges have been assigned for all events. Although a large number of shocks are listed with magnitudes of 6.0 and greater, none larger than 7.7 is known. The 64-item bibliography is a comprehensive list of source material on Nicaraguan seismicity.
On the ratio of P-wave to S-wave corner frequencies for shallow earthquake sources
Authors: Dahlen F. A.
Published: September 2021

abstract

We construct a theoretical three-dimensional kinematical model of shallow-focus earthquake faulting in order to investigate the ratio of the P- and S-wave corner frequencies of the far-field elastic radiation. We attempt to incorporate in this model all of the important gross kinematical features which would arise if ordinary mechanical friction should be the dominant traction resisting fault motion. These features include a self-similar nucleation at a single point, a subsonic spreading of rupture away from that point, and a termination of faulting by smooth deceleration. We show that the ratio of the P-wave corner frequency to the S-wave corner frequency for any model which has these features will be less than unity at all points on the focal sphere.
A note on the accuracy of computed ground displacements from strong-motion accelerograms
Authors: Trifunac M. D. , Lee V. W.
Published: September 2021

abstract

In this paper the accuracy of routine methods for processing strong-motion earthquake accelerograms (Trifunac, 1971, 1972; Hudson et al., 1971) has been tested by comparing displacement curves computed from the twice-integrated accelerograph recordings with displacement curves computed from displacement-meter measurements. The displacement meters have transducers with natural periods typically several seconds long. Agreement is found to be very good, suggesting that the methods used for routine processing of strong-motion accelerograms are quite accurate.
Is the sequence of earthquakes in Southern California, with aftershocks removed, Poissonian?
Authors: Gardner J. K. , Knopoff L.
Published: September 2021

Yes.
Seismicity and plate tectonics in south Central Alaska
Authors: Van Wormer J. D. , Davies J. , Gedney L.
Published: September 2021

Hypocenter distribution shows that the Benioff zone associated with the Aleutian arc terminates in interior Alaska some 75 km north of the Denali fault. There appears to be a break in the subducting Pacific plate in the Yentna River-Prince William Sound area which separates two seismically independent blocks, similar to the segmented structure reported for the central Aleutian arc.
Seismic regionalization in North America based on Average Regional Seismic Hazard Index
Authors: Howell B. F.
Published: September 2021

Cumulative Seismic Hazard Index (CSHI) is the logarithm of the sum of the seismic energies experienced at any location. Average Regional Seismic Hazard Index (ARSHI) is the regional average of Cumulative Hazard Index values normalized to 100 years. Both can be expressed in the same units as Mercalli intensity. ARSHI differs from previously proposed measures of seismicity in that it compensates for variations in the completeness of the historic record and for variations in the rate of attenuation of seismic energy with distance. More rapid attenutation of intensity with distance in the West than in the East reduces the difference in hazard between these regions.

In North America between 30° and 50° N latitude, ARSHI varies from 8.44 in the Western Nevada to 5.28 in the Canadian Shield and Plains provinces. Since ARSHI is measured on a logarithmic scale, this is a range of a factor of over 1,000 in average energy flux.

A trough of low seismicity between areas of high seismicity roughly coincides with areas of recent volcanic activity and high heat flow in parts of the Great Basin, the Columbia Plateau and adjoining areas. This low seismicity is interpreted as possibly being due to weakening of the crustal rocks by higher than normal temperatures. This interpretation would mean that low seismicity in this area is not evidence of a lack of tectonic activity. It is consistent with either a rising convection cell, a branch of the East Pacific Rise system underlying this area, or with igneous upwelling over an old subduction zone.
Reflections, rays, and reverberations
Authors: Kennett B. L. N.
Published: September 2021

abstract

The connection is established between conventional matrix methods for layered media and the reflection and transmission properties of a single layer. This interrelation is then used to set up an iterative approach to the calculation of reflection and transmission coefficients in multilayered media. This approach lends itself to a ray interpretation and allows estimates of errors involved in taking truncated partial ray expansions to be made. The special effects due to a free surface are also considered.
Self-similar circular shear cracks lacking cohesion
Authors: Burridge Robert , Levy Cesar
Published: September 2021

abstract

It has recently been shown (Burridge, 1973) that in two dimensions plane-strain shear cracks lacking cohesion may run at speeds ranging from the Rayleigh-wave to the S-wave speed or possibly at the P-wave speed. On the other hand, it has long been known that in antiplane strain, cracks lacking cohesion must run at least at the S-wave speed. Since locally at the edge of a three-dimensional crack there is a combination of plane and antiplane strain, we have sought and found solutions for circular shear cracks expanding at the S-wave speed and at the P-wave speed. These have finite shear tractions ahead of the crack and so may correspond to frictional sliding in the absence of cohesion.

The analysis combines the method of Kostrov (1964b) with the results of Burridge (1973).

We carry out a complete evaluation for the displacements and tractions on the fault plane, and far-field radiation for the S-wave-speed crack. The corresponding evaluations for the P-wave speed are not elementary and are not attempted here.

As far as the authors are aware, these are the first analytic solutions of three-dimensional crack problems which satisfy a physically plausible fracture criterion for failure under shear.
S-wave splitting: Key to earthquake prediction?
Authors: Ryall Alan , Savage William U.
Published: September 2021

abstract

This paper presents a detailed analysis of S-wave data for two areas in western Nevada. Some of these data were used by Gupta (1973b, c) as the basis for his claim that large premonitory changes in the extent of stress-induced S-wave splitting are observed for moderate-sized earthquakes in Nevada. Analysis of particle motion for an earthquake sequence near Slate Mountain indicates that changes in S-wave splitting did not occur during that sequence. For the Mina area, comparison of S-wave signatures for 158 events occurring over a 3-year period resulted in the identification of numerous events that would be considered anomalous by Gupta's criteria, but these were not followed by larger earthquakes. The present state of knowledge on crustal structure and seismic source parameters in the western Basin and Range province is not sufficient to discriminate between stress-induced velocity anisotropy and the many other factors that contribute to the complexity of S-wave signatures.
A new method for the analysis of multi-mode surface-wave dispersion: Application to Love-wave propagation in the east Pacific
Authors: Forsyth Donald W.
Published: September 2021

abstract

A new technique is presented for simultaneously measuring the average, regional phase velocity of two or more surface-wave modes, even if they travel with the same group velocity. Many observations are required over paths of varying length with earthquake sources of known focal mechanism. The phase of the signal observed at each station can be predicted if the initial phase of the source and the phase velocity and relative amplitude of each mode is known. The square of the difference between the observed phase and the predicted phase is summed over all paths for a set of trial phase velocities. The trial velocities which give the minimum sum correspond to the average phase velocity of each mode.

By applying this technique to Love-wave data from the east Pacific, the dispersion of the first higher Love mode was measured for the first time in an oceanic area. The phase velocity of the fundamental mode was found to increase with increasing age of the sea floor, probably as a result of the cooling of the oceanic lithosphere. The region was found to be anisotropic for Love-wave propagation, with the fastest velocities roughly perpendicular to the ridge. The degree of anisotropy appears to increase with increasing period.
Further studies on seismic discrimination
Authors: Evernden Jack F.
Published: September 2021

abstract

Further data on the shape of the Ms: mb(6.5 ≧ mb ≧ 4.0) curve for shallow-focus (D < 50 km) earthquakes are given along with theoretical explanations of the observed relationships. The frequency and probable cause of “anomalous” earthquakes is discussed. Capability of simple identification criteria (depth ≧ 50 km, detected Rayleigh waves of adequate amplitude, and/or location more then 25 km at sea), based on use of only a fraction of presently available data, is demonstrated. The magnitude of the mixed event (mixed surface waves of earthquakes) problem as it effects identification as well as procedures for circumventing the problem are demonstrated. Finally, recommendations are made for solving some other residual discrimination problems.
Premonitory seismic-wave phenomena before earthquakes near Fairview Peak, Nevada
Authors: Gupta Indra N.
Published: September 2021

abstract

Anomalous variations in three different seismic processes have been observed before an earthquake of magnitude 4 on May 14, 1971 in the Fairview Peak region of central Nevada. The data used are the three-component seismograms from Tonopah (TNP) and Battle Mountain (BMN) as well as the vertical-component seismograms from several other seismographic stations. The observed precursory phenomena are (1) reorientation of the compressive stress axis: evidence for this is based on clear reversals of first motion of Pg at certain stations together with reversal of wave form of the SV component of Sg at BMN; (2) vertical migration of hypocenters: the PmP phase is often distinctly observed in central Nevada and the observed temporal variations in t(PmP)−t(Pg) at TNP indicate generally upward migration of foci before the main event; (3) changes in the extent of S-wave splitting: a large precursory increase is observed along the tensile stress direction and a small premonitory decrease along the compression direction. Similar but unidentical results have been obtained before another earthquake of magnitude 4 whereas all events of magnitude 3.5 or larger have been preceded by anomalous S-wave splitting along the tension direction. The various observed pre-earthquake processes appear to be interrelated and may be explained in terms of recent laboratory and theoretical results when applied to the tectonics of central Nevada. It seems highly desirable to attempt simultaneous observations of anomalous changes in more than one seismic process.
Shear-wave attenuation along the San Andreas fault zone in central California
Authors: Bakun William H. , Bufe Charles G.
Published: September 2021

abstract

SH ground-displacement spectra (1 to 12 Hz) for 16 local earthquakes (Δ ≦ 18 km, 1.1 ≦ M ≦ 4.6) recorded at a common site situated atop the active trace of the San Andreas fault are used to estimate attenuation characteristics for propagation paths along the fault trace. t* = 0.10−0.13 (corresponding to an equivalent total path Qβ = 75−100) is appropriate for events with focal depths of ∼ 10 km.

Propagation-path effects, and not processes at the earthquake source, control corner frequencies for small (M ≲ 3) earthquakes for these highly attenuating paths. The results obtained here suggest that as a rule of thumb, if the true equivalent total path Q is as low as 4·ƒc·t, where ƒc is the estimated corner frequency and t the travel time, the corner frequency estimate is determined by propagation-path effects, not by processes at the earthquake source. In these cases, reliable estimates of source parameters can only be obtained if the appropriate propagation-path corrections are known.

Using Brune's model of shear-wave spectra, source dimensions L = 2r of less than 250 meters and stress drops greater than about 110 bar are estimated for the smaller events (1.1 ≦ M ≦ 2.2), using the equivalent total path Qβ obtained here. The seismic moments obtained in this study, together with data for larger central California events (2.4 ≦ ML ≦ 5.1) obtained by Johnson and McEvilly (1974), imply a linear log seismic moment-magnitude relation for 1 < ML < 5

log ⁡ 10 ( M 0 ) = ( 16.2 ± 0.1 ) + ( 1.52 ± 0.05 ) M L .
A note on the nonlinear response of the pendulous accelerometer
Authors: Rodgers P. W.
Published: September 2021

abstract

When the pendulous accelerometer experiences large off-axis acceleration in a direction which produces significant along-the-boom acceleration, the dynamics of the instrument are altered and it becomes nonlinear in its response. The response to an off-axis horizontal acceleration step is derived and found to exhibit small changes in damping, overshoot, damped resonant frequency, and final value of boom position. The size of these effects is negligible for all but the largest accelerations and even then acceptable. The change in overshoot is the largest, about 5 per cent, for an AR-240 strong-motion accelerograph subjected to a 1-g horizontal acceleration step at 45° to the sensitive axis.

An expression is developed for the steady-state response to off-axis sinusoidal acceleration. In addition to the proper response, it contains both a double frequency term and a constant offset. The size of these terms is discussed and an example is given.
Prediction of pressure-generated earth motion using optimum filters
Authors: Douze E. J. , Sorrells G. G.
Published: September 2021

abstract

The performance of long-period seismographs is often seriously degraded by atmospheric pressure variation; the problem is particularly severe at periods greater than 20 sec. The pressure variations associated with wind-generated turbulence and acoustic waves are sufficient to deform the surface of the Earth, thus adding to the background noise level recorded by the seismometer. If microbarographs are operated together with the seismograph system, a large percentage of the atmospherically generated noise can be eliminated by the use of optimum filters. The filters are designed based on the least-mean-squares criterion, with the seismograph time trace as the desired output and the microbarographs as the inputs. Single-channel filters, using only one microbarograph, located at the seismometer vault are used to attenuate wind-generated noise. In order to attenuate the noise on windless days from other pressure sources, multichannel filtering is usually necessary and therefore an array of microbarographs is required. The filters used to predict the wind-generated noise are shown to be stable despite the complicated source. The performance of the multichannel varies widely depending on the structure of pressure variations predominating in the atmosphere.
Attenuation of Modified Mercalli intensity with distance from the epicenter
Authors: Howell B. F. , Schultz T. R.
Published: September 2021

abstract

Thirteen simple formulas describing the attenuation of Modified Mercalli (MM) intensity are compared to determine which best predicts observed values in North America. The equation (19) ln I = ln I o + a 2 − b 2 ln Δ − c 2 Δ based on the assumption that intensity is related to energy by the equation (12) I = k E P appears to be the most useful, although it is not the most precise. P was found to be approximately 1/6, indicating that MM intensity is proportional to the sixth root of energy or the cube root of amplitude.

The United States and southern Canada are divided into three attenuation provinces: a San Andreas province with an energy absorption coefficient of 0.015/km, an Eastern province with an absorption coefficient of 0.0031/km and a Cordilleran province with an absorption coefficient of 0.0063/km.

The different rates of absorption can be explained as the result of slightly greater average focal depths in the East than in the West, although the data are too scattered to prove that this is the cause. Greater depth of focus, especially if low-angle faulting is involved, would explain the lack of surface displacement with eastern earthquakes.
The effect of sonic rupture velocity on the ratio of S to P corner frequencies
Authors: Burridge R.
Published: September 2021

abstract

In a recent paper Dahlen (1974) has used a simple model of shallow-focus earthquake faulting to study the ratio of S to P corner frequencies. The model predicts higher S than P corner frequencies, but, as he points out, observational studies have indicated the reverse.

It has been shown by Burridge (1973) and Burridge and Levy (1974) that rupture speeds up to the P-wave speed are to be expected on a purely frictional fault lacking cohesion but in Dahlen's calculations the rupture speed never exceeds the speed of S.

In this paper, we consider far-field radiation when the initial phase of rupture is a self-similar circular rupture zone spreading at the speed of P. For this model, we find that on 70 per cent of the focal sphere the P corner frequency is higher than that of S in accordance with the observations.
Microearthquakes in the Mono Lake-Northern Owens Valley, California, region from September 28 to October 18, 1970
Authors: Pitt A. M. , Steeples Don W.
Published: September 2021

A portable seismograph network was operated by the U.S. Geological Survey in the Mono Lake-northern Owens Valley, California, region in the autumn of 1970. From 20 days of recording, 74 microearthquakes were located. The geographic extent of the microearthquakes is similar to the historic seismicity from 1934 to 1970. Focal mechanisms are mostly right-lateral strike slip; one very good dip-slip solution was obtained. The relative tension axis was found to be very nearly east-west.
The use of duration as a measure of seismic moment and magnitude
Authors: Herrmann Robert B.
Published: September 2021

The observed relationship between magnitude and duration is shown to be a result of the particular shape of the signal coda as a function of time. If the envelope of the coda follows a t−q relationship with increasing time, then the magnitude, mτ, based on a duration τ is consequently of the form

m τ = q log ⁡ 10 τ + r .

A study of the duration-magnitude and duration-moment relationships for a set of central United States earthquakes indicates that the linear relationship between mτ and log10τ is valid only over a limited range. The departure from the simple linear dependence is explained in terms of instrumental response and the shift of the source-spectrum corner frequency with increasing event size.
The complex envelope in seismic signal analysis
Authors: Farnbach John S.
Published: September 2021

Some practical implications of the complex envelope representation of seismic signals are presented. Beginning with a look at an artificially constructed signal and proceeding to seismic records, it is seen that the complex envelope is more amenable to visual interpretation than the real signal itself. This is attributed to the natural separation of amplitude information from angle information afforded by the complex representation, and examples of arrival time measurement and P-coda correlation suggest that this leads to concrete seismological benefits. On this basis, it is suggested that the complex envelope may be a useful tool in seismic signal analysis.
Short-period Rayleigh-wave dispersion across the Tibetan Plateau
Authors: Chen W. P. , Molnar P.
Published: September 2021

Well-dispersed Rayleigh waves within the period range of 4 to 11 sec are observed at New Delhi (NDI) and Shillong (SHL), India, for seven earthquakes near and in the Tibetan Plateau from 1963 to 1971. The dispersion curves and the simply dispersed wave forms suggest a prominent overlying wave guide, probably sediments, in the Tibetan area. The thickness of such sediments is most likely between 2.5 and 7.0 km. The simple wave trains, without much distortion due to multipathing, are consistent with a relatively inert, recent tectonism in Tibet.
A fast, accurate method for computing group-velocity partial derivatives for Rayleigh and Love modes
Authors: Rodi W. L. , Glover P. , Li T. M. C. , Alexander S. S.
Published: September 2021

A method for quickly and accurately calculating Rayleigh- and Love-mode group-velocity partial derivatives with respect to model parameters (m) is developed. The method requires computer codes that calculate C, U, and ∂C∂m|ω and employs numerical differentiation of ∂C∂m|ω to yield ∂U∂m|ω. The method is fast because ∂C∂m|ω and ∂U∂m|ω for all the model parameters can be obtained at a given frequency from only two solutions of the period equation. The accuracy of the method is established with two examples. For Love waves, the group-velocity partials computed by this method agree exactly with those obtained analytically by Novotny (1970). For Rayleigh waves, comparison with a “brute force” calculation of group-velocity partials showed agreement to the order of 0.00002. Systematic inversion of group-velocity data separately or in combination with phase-velocity data is computationally feasible using this method.
Refined hypocenters and accurate reliability estimates
Authors: Veith Karl F.
Published: September 2021

A new method of correcting station arrival times for systematic source and station effects has been developed. The method yields source-region/station time (SRST) corrections which have a simple spatial variation and which are valid, in terms of yielding accurate focal depths and relative epicenters, over large areas. The method has been applied to over 200 earthquakes ranging in depth from about 10 to 650 km in the Kurile-Kamchatka-Okhotsk region. Resulting corrections are uniformly valid throughout an area of approximately one million square kilometers. Full utilization of the SRST corrections for the 25 close-in and 149 teleseismic stations was achieved by weighting each station's contribution to the computed hypocenters. The 95 per cent limits on the depth uncertainty cover the pP depth the appropriate percentage of the time regardless of the number or geometry of the stations in the observing network. The SRTS's for the close-in stations describe their arrival-time variations over the entire are structure and thus may be used in model studies to determine the structure and the epicenter bias.
Seismic intensities, “size” of earthquakes and related parameters
Authors: Evernden Jack F.
Published: September 2021

The simple model of an earthquake used in Evernden, et al. (1973) was extended to the conterminous United States and observed patterns of isoseismals for major earthquakes studied in relation to the model. Regional attenuation, a known major factor controlling isoseismal patterns, was quantitatively evaluated. Incorporating this regional variation into the model results in the prediction that in terms of energy released, the San Francisco earthquake of 1906 was 50 times as large as Owens Valley 1872 and more than 100 times larger than the Charleston 1886 and New Madrid 1811 earthquakes. All of these were probably of comparable “magnitude”. Other relevant parameters are investigated. Analysis of probability of occurrence of major earthquakes in the Eastern United States suggests average annual return times of intensity X and IX of thousands of years at least. Presently unknown local conditions may lead to much greater probabilities at some localities, and the importance of developing procedures for determining regions of abnormally high risk is stressed.
On crustal plates
Authors: Tocher Don
Published: September 2021

During the decade just past, developments in Seismology have played an active and central role in the development of the concept of Plate Tectonics. Observational Seismology has provided support for and verification of a number of the dynamic aspects of the hypotheses of continental drift, sea-floor spreading, transform faults and the underthrusting of the lithosphere at island arcs and some continental margins.

Those types of seismological evidence which bear on the question of the thickness of the lithosphere are either indirect or circumstantial, or both. As early as 1926, Gutenberg postulated the existence of a layer at a depth of 80 to 150 or 200 km, probably worldwide in extent, in which the velocities of seismic waves are slightly lower than in the immediately overlying layers. Some plate tectonics workers equate this low-velocity layer to the relatively-weak asthenosphere required by Plate Tectonics to underlie the stronger, more brittle lithosphere.

In this review, several lines of evidence are marshalled in support of a plate model of the continental crust in seismically active regions in which a layer of decoupling of an upper, lithospheric layer from the weaker substrate may lie in the crust itself at a depth of perhaps 10 to 15 km.
An analysis of tidal strain observations from the United States of America: I. The laterally homogeneous tide
Authors: Beaumont Christopher , Berger Jon
Published: September 2021

abstract

Tidal strain observations from seven observatories in the continental United States have been analyzed and the results compared with the tide predicted for a radially stratified earth model. Included in the predicted tide are the effects of ocean-tide loading for all of the major oceans. We find that on average the load strains contribute 44 per cent of the total M2 tidal strain and 13 per cent of the total O1 tidal strain. The differences between the predictions of the radially stratified earth model and the observations are significant. We conclude that: (1) Love numbers deduced from most strain observations are not representative of average earth properties. (2) The phase of the areal strain is neither independent of the tidal loading nor of the local geological structure. Hence, to use such phase observations as a measure of the anelastic properties of the Earth is incorrect.
Synthesis of teleseismic P waves from sources near sinking lithospheric slabs
Authors: Ward Ronald W. , Aki Keiiti
Published: September 2021

abstract

A wave theory method is used to determine the effect of a sinking lithospheric slab on short-period and long-period waves. We consider a simplified model of the lithospheric slab with a 10 per cent velocity contrast and compute both short-period and long-period theoretical seismograms from a P-wave source located in or near the slab. For this model, the ray-theoretical amplitude agrees quite well with the short-period amplitude. In the ray-theoretical shadow zone the long-period seismograms (15- to 25-sec dominant period) typically have amplitudes 50 per cent (or greater) of the direct P-wave amplitude and exhibit wave-form broadening. Similar wave-form broadening has been attributed to the dynamics of earthquake faulting. The effect of the lithosphere on long-period waves from nearby sources must be taken into account in studies which utilize the observed variation in wave-form broadening to infer earthquake source dynamics.
Seismotectonic maps of the European area
Authors: Kaila K. L. , Madhava Rao N.
Published: September 2021

abstract

Seismicity maps based on A value, b value, and return period for earthquakes with magnitude 6 and above have been prepared for the European area using the Kaila and Narain (1971) method. For the preparation of these maps, a modified relation A = 6.36b − 1.00 has been used instead of the earlier relation where A and b are constants in the cumulative regression curve represented by log N = A − bM. The A-value seismicity map also shows regional tectonics superimposed on it, thus yielding the seismotectonic map of Europe. These seismicity maps reveal that the European area consists of seven main high seismic activity zones named as the Balkan high, the Aegean high, the Apennine-sicilian high, the Alps high, the Carpathian high, the Saharan-Pyrenees high and the Iceland-Arctic high which are described in detail with their relationship to regional tectonics. The b values determined by the new method and shown on the b-value seismicity map are compared with those determined by other workers using earthquake regression curves for various regions of Europe and they show a very good agreement with each other.
A perturbation scheme for obtaining partial derivatives of Love-wave group-velocity dispersion
Authors: Kosloff Dan
Published: September 2021

abstract

A method is derived for obtaining partial derivatives of Love-wave group-velocity spectra for a layered medium using a second-order perturbation theory. These partials are a prerequisite for systematic inversion of group-velocity spectra but they are helpful as well in trial and error methods. Mathematically the equation of motion and boundary conditions for Love waves are a singular Sturm Liouville type eigenvalue problem. In the case of a fixed wave number, the eigenvalues are the negative of the square of the frequencies. Thus, by expressing the first- and second-order perturbations of the eigenvalues in terms of partial derivatives of the frequency with respect to the wave number and material parameters of the medium, one can relate these perturbations to group-velocity partials. The scheme should be relatively economical and easy to incorporate in Love-wave dispersion codes.