bluuebunny/crossref_metadata_2025 huggingface dataset:
Parental Leave Reforms in Finland 1977–2019 from a Diversity Perspective
Authors: Moring Anna , Lammi-Taskula Johanna
Published: July 2021

In Finland, all parents, regardless of gender, are eligible for parental leave and there are no restrictive eligibility criteria. In practice, however, the statutory leave options are not equally available to all parents. Since the 1970s, steps have been taken in redesigning the leave scheme to make it more inclusive. Several reforms have been made to promote equality, mainly between women and men, but also between diverse families, such as adoptive families, multiple-birth families or same-sex parent families. The ‘demotherisation’ of parental-leave rights has slowly shifted the focus from biological mothers to fathers and non-biological parents. In the most recent reforms, the focus has widened from equality between parents to include equality between children regardless of the form of the family that they are born or adopted into.
Capturing the Gender Gap in the Scope of Parenting Related Leave Policies Across Nations
Authors: Koslowski Alison
Published: July 2021

This article contributes to the conceptual and technical development of cross-national measurement and analysis of the gender gap in the scope of parenting related leave entitlements. That there is a gender gap in the scope of leave benefits is widely acknowledged, but it is rarely quantified. The nomenclature in use around leave policies is diverse and so a first step is to standardise categories and develop a unit of parenting related leave. There is considerable cross-national variation in the configuration of the scope of leave policies. As such, a second step is to consider how best to include the different dimensions of this scope (e.g., duration, payment level, individual parent versus family design) in an estimate of the gender gap in entitlement. Using data collated by the International Network on Leave Policies and Research, a gender gap indicator is created to contribute to our understanding of the inclusiveness of parenting related leave for men as compared to women. This indicator highlights that only two (Iceland and Norway) of 45 countries included in this analysis had achieved a zero-gender gap in terms of entitlement to ‘well-paid,’ individual parenting related leave during the first 18 months of a child’s life. The average gender gap for the countries in the analysis is between two to three months. Only seven countries offered more than two months leave to fathers as an individual entitlement. This is likely to be part of the explanation in many countries for lower leave taking practice by men compared to women.
The Festive Culture of Mining Plants in the Urals: The Dobryanka Case
Authors:   Perm State National Research University, Chernykh A. V.
Published: July 2021

В статье на основе документальных этнографических источников рубежа ХIХ-ХХ вв. реконструируется цикл календарных праздников и обрядов этого периода, сложившихся на одном из уральских заводов — Добрянском (западная часть Пермской губ.). На примере ритуалов встреча птиц кашке-плишке, проводы воды — «провожание Камы», Сергиев день, Троица и др. рассматриваются общие черты, особенности и закономерности развития и функционирования календарных праздников и обрядов в заводских поселениях Урала. В праздничной культуре таких поселений зафиксированы формирование особого производственного календаря и его связь с основными хозяйственными и праздничными циклами, становление на частных заводах особых «корпоративных» праздников, приуроченных к именинам владельца; сохранение архаичных форм традиционной обрядности, развитие календарной обрядности в направлении усиления досуговых форм, вымывание из многих ритуалов сакрального смысла, а также многослойность календарных традиций, активное усвоение и распространение новых, городских форм праздничной культуры. Прослежено, что праздничная культура заводских поселений занимала промежуточное место между сельскими крестьянскими и городскими формами народного календаря. Каждая из особенностей календарной обрядности заводских поселений рассмотрена на этнографических примерах того или иного праздничного цикла. Выявленные особенности позволяют сделать вывод о бытовании в заводских поселениях Урала особых форм традиционной культуры с уникальной спецификой.
Happy Marriages Are Blessed in the Heavens, Unhappy Ones Cause Poverty: A View on Women in Usun-Debeskertu-Khan’s Instructions
Authors:   Kalmyk Scientific Center, Russian Academy of Sciences, Bicheev B.A.
Published: July 2021

В статье рассматриваются традиционные представления о женщине и браке на основе наставлений, приписываемых правителю эпохи «религиозных царей» Усун-Дебескерту-хану и его министрам. Особое внимание уделено женским добродетелям, из которых главная — приверженность долгу перед мужем и детьми. Показано, что требования к женщинам благородного происхождения были выше, чем к остальным, но все они вполне реальные. Это подтверждено историческими свидетельствами. Приведены суждения об отрицательных женских качествах, которые обусловлены необузданными эмоциями, заставляющими забыть об общепринятых нормах поведения. Анализ наставлений, касающихся брака, показал, что в них наиболее явственно проявляется влияние буддизма, который, используя разные формы проповеди, в т.ч. дидактические сочинения, придал брачному союзу новое духовное содержание. Выделены три вида брака, условно обозначенные как «небесный», «земной» и «адский». Раскрываются причины счастливых и несчастливых брачных союзов, связанные, в первую очередь, с указанными в наставлениях женскими качествами. Гармоничное сосуществование в большей степени зависит от женщины.
Activity Approach in Teacher Education
Authors: Margolis A.A.
Published: July 2021

The paper addresses the subject matter and outcomes of the project on modernization of teacher education in Russia (2014—2017) aimed at enhancing professional development of future teachers and bringing it into compliance with the professional standard for teachers as well as with the federal state educational standards (standard-driven reform). I describe the theoretical concept behind the new activity-based model of teacher training which was developed and subsequently tested in the course of the project implementation. Also, I highlight several unresolved issues in teacher training and put forward some suggestions for the next stage of teacher education development.
On the Question of Intergenerational Differences in the Social Well-Being of Adolescents: Life Position and Assessment of Threat Significance
Authors: Sobkin V.S. , Kalashnikova E.A.
Published: July 2021

The article examines the specifics of social well-being in teenagers based on the opinions of 4,837 middle and high school students obtained during an anonymous questionnaire survey in 2020. The questionnaire included closed questions about priorities in life values, emotional assessment of future prospects, plans for the future and assessment of the significance of threats from the social environment. When analyzing the empirical material, the influence of demographic and social stratification factors is considered. Special attention is paid to identifying the relationships between values, the clarity of plans, the assessment of life success and possible social threats, taking into account the influence of gender and age characteristics. Based on the data comparison of a monitoring questionnaire for students of grades 9 and 11 conducted in 2010 (993 respondents) and 2020 (1327 respondents), using mathematical procedures of factor analysis, the characteristic changes in the social well-being of adolescents were identified that have occurred over the past 10 years. Modern teenagers plan their future more carefully, and the complex of life values associated with self-realization in the educational, cultural and professional spheres is more significant to them. At the same time, the values associated with successful implementation in family life have become less significant; the possibilities to provide for oneself are assessed as real social risks, and the tendencies of infantilization are increasing. In general, the set of indicators of social well-being used in this work can be used in psychological and pedagogical programs to study the sociocultural features of socialization in students of adolescent and young age.
Psychological and Didactic Issues of Digital Textbooks Creation
Authors: Granik G.G. , Borisenko N.A.
Published: July 2021

The article substantiates a special approach to the development of a school digital textbook which is based on the idea of synthesis of psychological, didactic, methodological, and subject knowledge with the priority of using the psychic pat- terns of personality development. To denote an interactive electronic textbook, it is proposed to use the term “digital textbook” (DT). From the methodological point of view, DT is regarded as an “enhanced” paper textbook, characterized by such basic properties as interactivity, multimodality, hypertextuality, and personality. The question about the development of the digital textbook concept before the textbook creation is raised. A number of psychological and didactic problems are discussed, such as: 1) the relationship between paper and digital textbooks (an option of the simultaneous use of both textbook formats is proposed); 2) DT as an essential com- ponent of the digital educational environment (the maximum effect is achieved if every DT is integrated into a single system as well as educational environment); 3) the features of reading on screen (non-linear nature, activity and dynamism, superficial understanding, greater fatigue, etc.). Besides, the article analyzes the advantages and disadvantages of DT and presents the results of its effectiveness based on the foreign studies. A conclusion was made that the wide-scale introduction of DT is possible solely when its positive influence not only on academic performance, but also on the cognitive development of students is revealed.
PERCEPÇÃO DE PROFESSORES SOBRE ACESSIBILIDADE PARA ESTUDANTES AUTISTAS NO ENSINO SUPERIOR
Authors: Cristina da Silva Solange , Ribeiro Schneider Daniela
Published: July 2021

Este artigo analisa as condições de acessibilidade de estudantes com autismo no ensino superior a partir da percepção de professores(as). A pesquisa qualitativa, optou pelo questionário online como técnica de coleta de informações, com questões aberta e fechadas. Participaram dez professores(as) de estudantes com autismo matriculados em suas disciplinas de graduação. A análise dos dados teve como base a análise de conteúdo. Os resultados evidenciaram ações dos docentes voltadas à acessibilidade para os estudantes com autismo se centram mais na dimensão metodológica do que na atitudinal. Destacam a importância do diagnóstico e a tendência tê-lo como determinante da ação pedagógica. Denunciam as condições imposta pelas IES, como o número alto de estudantes por turma e as demandas cotidianas na instituição, os quais dificultam o trabalho docente.
DESAFIOS DO ALUNO COM DEFICIÊNCIA NEUROMOTORA NA EDUCAÇÃO BÁSICA DA REDE MUNICIPAL DE CURAÇÁ-BA
Authors: Remígio Florêncio Roberto , Dantas da Paixão Martins
Published: July 2021

Com o objetivo de compreender e analisar o processo de aprendizagem de um aluno com deficiência, no 5º ano do Ensino Fundamental I, em uma escola municipal da rede pública na cidade de Curaçá-BA, este estudo propõe uma análise sobre a Educação Inclusiva nas escolas regulares. Optou-se por uma pesquisa de campo, com abordagem qualitativa, com aspectos técnicos e metodológicos que direcionam para a compreensão dos dados pesquisados a partir de um estudo de caso. Durante o processo da pesquisa, foram realizadas visitas ao espaço escolar e a observação participante em acompanhamento das aulas. Recorreu-se à literatura em busca de compreender conceitos de diferentes autores da área, além de relacionar teoria e prática na busca pela compreensão dos fenômenos, através dos dados identificados. Os resultados estão apresentados de forma clara, objetivando oportunizar uma análise crítica acerca da prática inclusiva nas escolas regulares da rede de ensino municipal. As considerações finais deste estudo não apresentam conclusões, mas indícios da situação de formação no trabalho dos profissionais da educação que contribuem para a aprendizagem dos estudantes com deficiência.
Seismicity and focal mechanisms associated with the subduction of the Juan de Fuca plate beneath the Olympic Peninsula, Washington
Authors: Taber J. John , Smith Stewart W.
Published: July 2021

Two and a half years of data from an expanded, telemetered seismic network on the Olympic Peninsula reinforce the conclusion that the Juan de Fuca plate is subducting beneath Washington. However, the rate of seismicity is presently much lower than typical rates at other convergent margins.

The located earthquakes can be divided into two groups on the basis of depth. At the coast, a shallow zone extends to a depth of approximately 20 km while a deep zone begins at 25 km. On the eastern edge of the Peninsula, the shallow zone has thickened to 30 km and the depth to the top of the deep zone has increased to 45 km. The rate of crustal seismicity is much lower on the Peninsula than in the adjacent Puget Sound region. The deep zone is 5 to 10 km thick and dips to the east at an angle of about 11°. The deep events appear to be occurring in the upper part of the subducting oceanic lithosphere.

Focal mechanisms were constructed for 16 events in the suite of deep events with magnitudes ranging from 1.6 to 4.3. The solutions show primarily normal faulting with the P axes normal to the slab and the T axes displaying a range of angles within the slab with the average T axis in the downdip direction. Small events with down-dip tension in the downgoing slab are consistent with the slab sinking under its own weight. Several strike-slip events may be caused by a shearing within the slab. These features are consistent with ongoing subduction of the Juan de Fuca plate beneath North America.
On the earthquake hazards of Puerto Rico and the Virgin Islands
Authors: McCann William R.
Published: July 2021

Puerto Rico and the Virgin Islands are located near the northeastern corner of the Caribbean seismic zone. Numerous large earthquakes have struck these islands, some with disastrous results. The 400-yr-long earthquake record of Puerto Rico describes shocks affecting nearly all portions of the island. The last destructive shock, in 1918 (7.5 MS), did not occur along the main seismic zone, but rather on an intraplate fault near Mona Canyon off the northwest coast. A possible great earthquake in 1787 (8 to 8.25 MS) appears to have occurred along the main seismic zone near the Puerto Rico Trench to the north of the island, but data for the event are scarce.

A disastrous earthquake in the Virgin Islands (1867, 7.5 MS) also occurred on an intraplate fault. This fault is one of a series that bound the Anegada Trough separating Saint Croix from the main chain of the Virgin Islands.

Seafloor morphology, microearthquakes, and the record of historic earthquakes define a zone of deformation extending from the Puerto Rico Trench, northeast of the Virgin Islands, trending southwest along the Anegada Trough and then westerly along the Muertos Trough. The Muertos Trough is the locus of convergence between the floor of the Caribbean Sea and Puerto Rico. Maximum dimensions of future large earthquakes are inferred from sizes of blocks in the Anegada and Muertos Troughs as well as Mona Canyon. Shocks as large as 7.5 can occur on these intraplate faults. Although strain rates on these faults may be an order of magnitude less than on faults in the Puerto Rico Trench, the large number of potential sources suggest that damaging earthquakes in this part of the Caribbean can come from either the Puerto Rico Trench or the intraplate faults with nearly equal probability.
Surface motion of topographical irregularities for incidentP, SV,and Rayleigh waves
Authors: Sánchez-Sesma Francisco J. , Bravo Miguel A. , Herrera Ismael
Published: July 2021

Trefftz's method is applied to solve the diffraction of P, SV, and Rayleigh waves by surface irregularities in an elastic, isotropic and homogeneous half-space. The diffracted wave fields are constructed with linear combinations of solutions which form c-complete or T-complete (T after Trefftz) families for the wave equation. Boundary conditions are satisfied in the least-squares sense on the irregularity and on a finite interval of the half-space surface. Excellent agreement was found with the solution by Wong (1982).
New probabilistic strong seismic ground motion maps of Canada
Authors: Basham P. W. , Weichert D. H. , Anglin F. M. , Berry M. J.
Published: July 2021

New probabilistic strong seismic ground motion maps of Canada are derived by applying the “Cornell-McGuire” method to 32 earthquake source zones in Canada and adjacent regions. Peak horizontal acceleration and peak horizontal velocity are mapped to depict strong ground motion in the frequency ranges near 5 Hz and near 1 Hz, respectively.

Some earthquake source zones are well defined on the basis of both tectonics and average seismicity rates, but a lack of understanding of the near-field effects of the large earthquakes prohibits accurate estimates of ground motion in their vicinity. Some source zones have no known large-scale crustal features or zones of weakness that can explain the seismicity and must, therefore, be defined simply as concentrations of seismic activity with no geological or geophysical controls on the boundaries. Other source zones lack information on low-magnitude seismicity that would be representative of longer periods of time.

A significant source of uncertainty in the ground motion estimates is introduced by the uncertainty in strong ground motion attenuation relations, particularly in the near-field of large earthquakes and particularly in eastern Canada where no strong motion data are available for earthquakes larger than magnitude 5. Valid estimates can be made of relative levels of probabilistic strong ground motion on a regional basis at moderate probabilities; however, the simple peak ground motion parameters are not sufficient for engineering design purposes in the immediate vicinity of large earthquakes.

A comparison of the new probabilistic ground motion estimates at the Canada-United States border with equivalent estimates made in the United States reveals that peak acceleration contours match well in the British Columbia-Washington State, Yukon-Alaska, and Lake Ontario border regions. Canadian peak velocities are a factor of two higher near the British Columbia-Washington State border. Canadian peak accelerations are higher in the border regions of eastern Canada influenced by the Charlevoix zone, and in regions of the Alaska Panhandle-British Columbia border influenced by the active Queen Charlotte and Fairweather fault zones.

The new ground motion estimates are used to produce new peak acceleration and peak velocity zoning maps to replace the 1970 (peak acceleration) zoning map in the National Building Code of Canada. The acceleration and velocity maps provide independent ground motion reference levels for small rigid structures and taller flexible structures, respectively. Compared to the 1970 map with four zones, the new maps with seven zones have a finer subdivision of zoning in moderate risk areas and additional zones in the high risk areas. A change in probability of exceedence from 0.01 per annum on the 1970 map to 10 per cent in 50 yr on the new maps, and the addition of velocity as a zoning parameter, have necessitated changes in the seismic design provisions. These revisions will be incorporated into the 1985 edition of the Code.
Survey of damages during the Dhamar earthquake of 13 December 1982 in the Yemen Arab Republic
Authors: Arya A. S. , Srivastava L. S. , Gupta Satyendra P.
Published: July 2021

The Dhamar province of the Yemen Arab Republic was shaken on 13 December 1982 by a moderate earthquake. The earthquake caused considerable loss of life and different degrees of damage to the traditional houses in the area. The most common forms of construction, consisting of stone masonry and adobe, suffered very extensive damage. The destruction of houses was mainly due to failure of the superstructure and none due to the movement of foundations. An above-ground reinforced concrete water tank also collapsed. Ground fissures, rupture of stones on a hill side, rock falls, and slides were also observed. An isoseismal map of the earthquake-damaged area is also presented.
Underground and ridge site effects: A comparison of observation and theory
Authors: Bard Pierre-Yves , Tucker Brian E.
Published: July 2021

This paper compares experimental observations and theoretical predictions of the effects of underground and ridge sites on the amplitude of seismic waves.

Observations by Tucker et al. (1984) of narrow-band, earthquake-independent site effects of a factor of 3 at underground sites down to a depth of 40 m can be predicted well using a one-dimensional theoretical model and information about seismic velocity as a function of depth. The observations can be explained as being due to the interference of upcoming, incident, and downgoing, surface-reflected waves within a thin, low-velocity, near-surface layer. An important effect of this layer is to make the interference pattern at shallow depths (i.e., within the layer) insensitive to the incidence angle of the incoming signal and, thus, stable from earthquake to earthquake. Our model suggests that at depths of about 100 m, site effects as great as a factor of 6 would be observed at about 5 Hz, while at much greater depths, site effects would be small. Currently available theoretical techniques are sufficient to assess the expected ground motion at underground sites provided that the velocity profile is known. This is useful for buried pipes, tunnels, and critical storage facilities.

Observations by Tucker et al. (1984) and others of narrow-band, earthquake-independent site effects of about a factor of 8 on ridges cannot be predicted completely using theoretical techniques currently available to us. Accurate predictions could probably be made with a model that included the effects of ridge topography, neighboring topography, and near-surface velocity gradients. Use of such a model, if it were available, would require detailed, expensive knowledge of regional topography and velocity structure. The observed insensitivity of ridge site effects on ridges to incidence angle can, however, be explained with existing theoretical models as being due to a near-surface, low-velocity layer. The size of site effects on ridges and the stability of these effects from earthquake to earthquake suggests that they should be considered when interpreting seismograms obtained from ridge sites and when designing structures, such as communication antennae and power transmission towers, that will be located on mountain ridges. Accurate determination of the site effects of ridges and mountain tops can probably best be done using experimental techniques.
Three-dimensional ultrasonic modeling of Rayleigh wave propagation
Authors: Bullitt John T. , Toksöz M. Nafi
Published: July 2021

The effects of topographic features on Rayleigh wave propagation and scattoring are investigated in the laboratory using three-dimensional ultrasonic models. Starting from simple steps, different topographic features are modeled. The effects of these features on Rayleigh wave transmission and scattering are examined as a function of wavelength and as a function of angle of incidence. In general, backscattered or reflected Rayleigh waves are small compared to transmitted waves. A significant fraction of the Rayleigh wave energy is scattered into body waves. Transmission and reflection coefficients (transmitted or reflected energy/incident energy) computed from spectral ratios vary strongly with incidence angle. At wavelengths equal to twice the step height, the fraction of incident energy scattered into body waves ranges from more than 90 per cent at normal incidence to about zero at near-grazing incidence. At each angle, transmission coefficients vary strongly with frequency. Because of frequency-dependent phase shifts, the transmitted and reflected waves are distorted.

The effect of the steps on the propagation of Rayleigh waves is demonstrated by convolving synthetic dispersed wave trains with the impulse response of the scale models. The ocean-continent margin of the Western United States is modeled as a 60° ramp scaled to 60 km height. The Tibetan Plateau is modeled as a broad mesa scaled to 40 km height. In both models, azimuthal dependence of transmitted Rayleigh waves is similar to that observed at WWSSN stations for Rayleigh waves crossing the modeled terrestrial structures.
Stress trajectories across the Northeast Alaska Range
Authors: Gedney Larry
Published: July 2021

A single earthquake on the southeast portion of the Denali fault in 1981 and two earthquake swarms occurring in 1981 and 1984 on the northern flanks of the Alaska Range south of Fairbanks indicate that the axis of maximum horizontal compressive stress is oriented in a NW-SE direction in the region. This is in accord with earlier findings by Nakamura et al. (1980) that tectonic trends signal a similar orientation of maximum horizontal compressive stress trajectories here.
Some observations on strong-motion earthquake measurement using a digital accelerograph
Authors: Iwan Wilfred D. , Moser Michael A. , Peng Chia-Yen
Published: July 2021

This paper presents results of a study of some of the characteristics of a PDR-1 digital strong-motion accelerograph. Results are presented for laboratory tests of the background noise level of the instrument, and these results are compared with previously reported observations for optical instruments. Noise levels for the digital instrument are found to be one or two orders of magnitude lower than for an analog optimal instrument. The paper discusses determination of displacement from acceleration data, and results of laboratory tests are presented. An instrument anomaly in the FBA-13 transducer is identified, a simple data correction algorithm proposed, and examples given. The paper also presents detailed results of a comparison of earthquake records obtained from side-by-side digital and optical analog instruments during an aftershock of the 1983 Coalinga earthquake.
The great Jalisco, Mexico, earthquakes of 1932: Subduction of the Rivera plate
Authors: Singh S. K. , Ponce L. , Nishenko S. P.
Published: July 2021

We have analyzed seismograms of the 3 June 1932 (Ms = 8.2) and the 18 June 1932 (Ms = 7.8) Jalisco earthquakes and their aftershocks at Manzanillo (MNZ), Guadalajara (GUM), and Tacubaya (TAC). The aftershocks locations, the first motions at MNZ, and the isoseismic maps of the two main shocks strongly suggest that: (a) the 3 June 1932 earthquake initiated NW of but close to MNZ and propagated NW for an estimated length of rupture of 220 km; (b) the 18 June 1932 earthquake nucleated SW of MNZ (offshore) and perhaps ruptured a length of about 60 km; and (c) the width of rupture was approximately 80 km. There is no evidence of events occurring SE of MNZ even up to 1 1/2 yr after the first main shock. A gap of about 60 km remains between the aftershock areas of the 1932 Jalisco and the 1973 Colima earthquakes whose seismic potential is unknown. Although the boundary between the Rivera and Cocos plates is uncertain, there is little doubt that the 1932 earthquakes broke the shallow part of the Rivera subduction zone. Our results may help in quantifying seismic potential of tectonically similar areas such as the Juan de Fuca subduction zone in the NW United States.
Laboratory test of apparent attenuation formulas
Authors: Menke William , Witte Dean , Chen Rolin
Published: July 2021

We measure the apparent attenuation of P waves propagating through a three-dimensional scattering medium (a three-dimensional aluminum block containing a random assemblage of cylindrical voids). The observed apparent attenuation is compared to that predicted by a single scattering approximation. At low frequencies, both the amount of attenuation and its variation with frequency are well predicted. At intermediate and high frequencies, the agreement is poorer. Observed phase shifts are very different from those predicted by the Kramers-Krönig relations.
Analysis of the trade-off between hypocentral depth and source time function
Authors: Christensen Douglas H. , Ruff Larry J.
Published: July 2021

Focal depth determination for shallow (≤60 km) intermediate-size (Ms ≈ 6.5 to 7.5) earthquakes continues to be problematic. For these events, the depth phases (i.e., pP and sP) are not distinctly separated in time, and thus synthetic modeling of wave shapes becomes necessary. Unfortunately, the uniqueness of the solution is not easily determined because of the trade-off between various focal parameters. We have investigated the trade-off between depth and source function both theoretically and experimentally. The changes in the Green's function caused by an incorrect assumed depth can almost always be compensated by changes in the source function, producing the same “observed” seismogram. Thus, there is considerable trade-off between depth and the source function. Perturbing the depth from the “true” depth leads to a more “complicated” source function. The “simplest” source function then pinpoints the true depth. We have used two different measures of simplicity, the varimax norm (Vmax) and the half-absolute moment time (T12); both measures successfully characterize the complications that appear in the source functions for incorrect assumed depths. The true depth of an event can be interpreted from the resultant Vmax versus depth and T12 versus depth curves. Thus, we have a technique that determines the depth range of faulting in a systematic quantitative fashion. Our observations from the synthetic study have been applied to an outer-rise event off the coast of central Chile (16 October 1981; Ms = 7.2), to an event in southern Mexico (24 October 1980; Ms = 7.0), and to the Borrego Mountain event in southern California (9 April 1968; Ms = 6.4) resulting in faulting depth ranges of 0 to 20 ± 5 km, 60 to 70 ± 5 km, and 10 to 14 ± 5 km, respectively.
Effects of magnitude uncertainties on estimating the parameters in the Gutenberg-Richter frequency-magnitude law
Authors: Tinti Stefano , Mulargia Francesco
Published: July 2021

The evaluation of the parameters in the Gutenberg-Richter (GR) frequency-magnitude law log Nr = a − bm is shown to be strongly affected by magnitude uncertainties. If the magnitude errors are assumed to be distributed normally with standard deviation σ, the observed magnitude that we call the “apparent magnitude,” becomes a random variable, and the frequency-apparent magnitude law differs from the GR relation. We show that there is a range of magnitudes within which this law may be approximated as log Na = a − bm + γ2log(e). Here, γ2 = β2σ2/2, [β = b/log(e)], and Na stands for the apparent number of the earthquakes. As both the true and the apparent magnitude curves have the same slope on a logarithmic graph, the estimators usually employed for β remain valid. However, the usual estimators for a are biased by a quantity which is a quadratic function of the error standard deviation σ and of β. This implies that the apparent number, Na, of earthquakes exceeding a given magnitude tends to be larger than the real number Nr and for realistic values of a and b (or β), Na is expected to be even as large as twice Nr. The implications of the magnitude variability on the seismic risk analysis are also considered: in particular, the evaluations of the attenuation law parameters and of the exceedance probability of the ground motion peak acceleration are shown to be affected.
An earthquake detector employing frequency domain techniques
Authors: Gledhill K. R.
Published: July 2021

A single-station real-time earthquake detector has been developed which operates in the frequency domain. Frequency domain operation is possible because the method of calculation of the discrete Fourier transform and the data format have been adapted to suit the architecture of the microprocessor used. A test period of 10 days resulted in a detection reliability of greater than 95 per cent, with a false detection rate of less than 10 per cent (241 earthquakes total sample). The spectral detector outperforms time domain detectors in two respects. It is much more likely to identify the more distant, emergent earthquakes, and those recorded with a low signal-to-noise ratio. The algorithm operates on a Motorola MC6809 microprocessor and uses less than a quarter of the available time at a 50-Hz sampling frequency.
The “Report” of the 1868 Haywards earthquake
Authors: Aldrich Michele L. , Bolt Bruce A. , Leviton Alan E. , Rodda Peter U.
Published: July 2021

An important question on the major 1868 northern California earthquake centered near Hayward is whether a comprehensive field report was ever written, and if so, was the report suppressed. Documentation bearing on this question includes contemporary minutes and proceedings of the California Academy of Sciences, a report in 1870 by James Blake on the work of a subcommittee of the Committee on Earthquake Topics, contemporary newspaper accounts, a treatise published in 1868 by Thomas Rowlandson, and a letter written by George Davidson in 1908, the contents of which were made public in 1982. George Davidson claimed that a report had been prepared but was suppressed. The claim is not supported by either James Blake or Thomas Rowlandson, who indicate that lack of funds and internal dissension prevented completion of the investigation or presentation of a final report.
Estimation of scalar moments from explosion-generated surface waves
Authors: Stevens Jeffry L.
Published: July 2021

Rayleigh waves from underground nuclear explosions are used to estimate scalar moments for 40 Nevada Test Site (NTS) explosions and 18 explosions at the Soviet East Kazakh test site. The Rayleigh wave spectrum is written as a product of functions that depend on the elastic structure of the travel path, the elastic structure of the source region, and the Q structure of the path. We use our results to examine the world-wide variability of each factor and the resulting variability of surface wave amplitudes. The path elastic structure and Q structure are found by inversion of Rayleigh wave phase and group velocities and spectral amplitudes. The Green's function derived from this structure is used to estimate the moments of explosions observed along the same path.

This procedure produces more consistent amplitude estimates than conventional magnitude measurements. Network scatter in log moment is typically 0.1. In contrast with time domain amplitudes, the elastic structure of the travel path causes little variability in spectral amplitudes. When the mantle Q is constrained to a value of approximately 100 at depths greater than 120 km, the inversion for Q and moment produces moments that remain constant with distance. Based on the best models available, surface waves from NTS explosions should be larger than surface waves from East Kazakh explosions with the same moment. Estimated scalar moments for the largest East Kazakh explosions since 1976 are smaller than the estimated moments for the largest NTS explosions for the same time period. This contrasts dramatically with mb values for the same events which show the opposite behavior.
Seismicity of the Sudan
Authors: Ambraseys N. N. , Adams R. D.
Published: July 2021

abstract

This paper presents a record of information on the seismicity of the Sudan. In addition to events for which only felt information exists, there are a number of early teleseismic locations of earthquakes which have been reexamined using information from contemporary station bulletins. Most activity is close to the southern borders of Sudan, near the African rift system, but the northeast is affected by earthquakes in the Red Sea, and the central intraplate region has also experienced earthquakes capable of producing damage.
Lateral velocity variations in Southern California. II. Results for the lower crust from Pn waves
Authors: Hearn Thomas M. , Clayton Robert W.
Published: July 2021

abstract

A tomographic inversion of the Pn arrivals in Southern California yields new information about wave velocities and topography on the Moho discontinuity. We produce maps of Pn velocity and Pn station delays. The Pn velocities do not show the dramatic correlation with surface faults that is found for the shallower Pg arrivals (Hearn and Clayton, 1986). This implies that the lower crust and mantle are largely decoupled from the upper crust. Undoubtedly, this is due to the different responses of the brittle upper crust and the ductile lower crust to tectonic and isostatic stresses. Detachment faults must play an important role in separating the crust.

In general, velocities on the American plate are higher than on the Pacific plate, but no distinct transition is observed. The Colorado River region has extremely thin crust due to basin-and-range type extension. The Transverse Ranges have a small root as seen in the station delays and which also results in slightly lower Pn velocities there. The Peninsula Ranges also have slow Pn velocities, but they do not have late station delays. Any root to the Peninsula Ranges must be very narrow. Isostatic balance must be maintained primarily through lateral density contrasts.
Site amplification of coda waves from local earthquakes in central California
Authors: Phillips W. Scott , Aki Keiiti
Published: July 2021

The goals of this study are two-fold: (1) to examine the site effect of coda waves, believed to be the average site effect of shear waves, in order to understand its spatial and frequency-dependent behavior, and (2) to learn what we can about the processes that generate the coda itself. We use digital data from over 90 earthquakes, each recorded by a subset of some 150 stations in the Coast Ranges of central California between San Francisco and San Luis Obispo. Results from the band 1.5 to 24 Hz indicate that site amplification depends strongly on surface geology and frequency. At low frequencies (1.5 to 3.0 Hz), changes in amplification up to a factor of 20 are observed; amplification generally varies inversely with deposit age at sediment sites and is lowest at granite and Franciscan (basement) sites. At high frequencies (6 to 24 Hz), the pattern changes. Many granite sites, the majority in the Gabilan range, exhibit increasing amplification with frequency relative to the average station. This behavior differs strikingly from that observed at sediment and Franciscan sites which roll-off at an intermediate rate, and many sediment sites adjacent to the San Andreas fault zone which decay away even more rapidly with frequency. These results can be explained qualitatively by appealing to variable near-site impedance and attenuation, however, complicating phenomena such as mode excitation in valley sediments must exist at low frequencies. Peaked behavior at a few hard rock sites at high frequency (12 Hz) currently lacks explanation. At a few sediment sites, the low-frequency excitation is so strong that the coda envelopes begin to take on different shapes. This contradicts the assumption based on previous observations that the coda shape is independent of source-receiver location, thus, some site measurements may be artificially high. The working model of coda waves as body-wave energy backscattered from randomly distributed inhomogeneities must be modified to include the possibility of efficient near-site resonance excited by incident direct and coda wave energy.
Interstation surface wave analysis by Frequency-domain Wiener deconvolution and modal isolation
Authors: Hwang H. J. , Mitchell B. J.
Published: July 2021

A new technique which combines frequency-domain Wiener filtering and modal isolation is developed for determining interstation phase velocities, group velocities, and attenuation coefficients for seismic surface waves. Frequency-domain Wiener filtering is more effective than time-domain Wiener filtering for the determination because it uses a smaller window lag which produces a smoother interstation Green's function. This leads to greater accuracy and stability when noise-contaminated data are analyzed. We optimize Wiener filtering in the frequency domain by applying two trapezoidal windows of different lags to the cross-correlation function between two stations and to the autocorrelation function of the first station, respectively. The windowed correlation functions are then transformed to the frequency domain. The interstation Green's function in this technique is the ratio of the smoothed cross-spectrum to the smoothed auto-spectrum of the first station. Frequency-domain Wiener filtering is equivalent to time-domain Wiener filtering when the same rectangular window is applied to both the correlation functions.

Wiener filtering, however, cannot efficiently remove higher mode interference when the higher modes are superimposed on the fundamental mode in the correlation functions. To more thoroughly eliminate the effects of such interference, phase-matched filtering or time-variable filtering can be employed to isolate one particular mode at each of two stations. Frequency-domain Wiener deconvolution is then applied to calculate the Green's function. The interstation group velocites can be obtained by applying the multiple filter technique to the Green's function, and can be refined by phase-matched filtering. The amplitude and phase spectra of the Green's function are used to calculate attenuation coefficients and phase velocities, respectively, for the interstation medium.

This new technique is compared with other methods by applying them to both noise-contaminated synthetic seismograms and real data. The proposed technique is found to be superior, particularly in period ranges where the signal-to-noise is low.
Surface displacement on the Imperial and Superstition Hills faults triggered by the Westmorland, California, earthquake of 26 April 1981
Authors: Sharp Robert V. , Rymer Michael J. , Lienkaemper James J.
Published: July 2021

Parts of the Imperial and the Superstition Hills faults moved right laterally at the ground surface at the time of or shortly following the ML 5.6 Westmorland earthquake of 26 April 1981. The displacements probably occurred before any significant aftershocks on either fault and thus are classed as triggered slips. Although the main shock was located in an exceptionally seismogenic part of Imperial Valley, about 20 km distant from either fault, no clear evidence of past surface faulting is known in the epicentral area. Horizontal displacement on the Imperial and Superstition Hills faults, southeast and southwest of the epicenter, respectively, reached maxima of 8 and 14 mm, and the discontinuous surface ruptures formed along approximately equal lengths of northern segments of the two structures (16.8 and 15.7 km, respectively). The maximum vertical component of slip measured on surface cracks on the Imperial fault (6 mm) was located on the west side of Mesquite basin near Harris Road. Leveling data at Harris Road suggest slightly larger vertical movement at the surface there. Fault dislocation modeling of this leveling data further suggests that the maximum shallow subsurface dip-slip component of the triggered movement was as much a factor of 4 larger than that measured at the fault trace. The map pattern of the rupture may reveal the principal strand among the several near the north end of the Imperial fault.

No surface displacement was found along traces of the Brawley fault zone, the San Andreas fault, or the part of the Coyote Creek fault that slipped during the 1968 Borrego Mountain earthquake. Ground search in the epicentral area of the main shock and in the widely dispersed aftershock region in northern Imperial Valley failed to locate any definite evidence of new surface faulting.
Variability in explosion body-wave magnitudes: An analysis of the RULISON/GASBUGGY anomaly
Authors: Murphy J. R. , Archambeau C. B.
Published: July 2021

An analysis of the RULISON/GASBUGGY mb anomaly is presented which encompasses comparative studies of near-regional, regional, and teleseismic data recorded from these two explosions, as well as theoretical simulation analyses of selected near-regional and teleseismic data sets. Previously proposed explanations for this mb anomaly, such as differences in explosive source coupling and variations in upper mantle attenuation beneath the two test sites, are critically examined and shown to be inconsistent with various aspects of the observed data. However, both long-period and short-period evidence is presented, which indicates that significant tectonic release accompanied the RULISON explosion. It is demonstrated that the short-period, near-regional SH observations from RULISON can be theoretically explained by an explosion-induced tectonic release equivalent to a 250 to 300 bar stress drop at the elastic radius of the explosion. The inferred prestress field is homogeneous to first order and oriented as a pure shear on planes dipping at about 45°, with normal, or dip-slip displacements occurring as a consequence of stress relaxation. Such a tectonic release mechanism would be expected to decrease the associated explosion mb value by more than 0.3 units and, therefore, can provide a quantitative explanation of the observed RULISON/GASBUGGY mb anomaly. We conclude that tectonic release can significantly affect the short-period teleseismic P waves from explosions, at least in cases where the tectonic stress is large and favorably oriented.
Estimation of slowness-dependent source and receiver corrections forP-wave travel times
Authors: Tralli David M. , Johnson Lane R.
Published: July 2021

Tectonically regionalized tau estimates are used to obtain seismic P-wave travel-time corrections for lateral variations in the Earth's crust and shallow-mantle velocity structure. The corrections, in the form of estimates of tau perturbations, are functions of slowness and are assessed for both the source and receiver regions. The functional form is derived analytically and allows interpretations of causative velocity anomalies. Corrections for both ray path endpoints constrain effects typically assigned solely to the receiver, thereby helping assess systematic errors in hypocentral parameters. Over 1.25 million ISC Bulletin P-wave ray paths are used to estimate tau perturbation functions for seven types of tectonic regions. Particular attention is given to the problem of uniformly sampling all tectonic regions at all propagation depths in the mantle.

Estimates of source and receiver tau perturbations are consistently less than 1 sec and show a definite and systematic difference between the travel-time correction functions for oceans and continents. Source tau perturbations are indicative of negative velocity anomalies in the shallow mantle beneath oceanic regions and positive anomalies beneath continental regions and oceanic trenches. Heterogeneity confined to the upper 250 km of the mantle suggests velocity variations within ±5 per cent of the lateral mean over a depth interval of approximately 100 km. Differences between the receiver and source perturbations for a common tectonic region are attributed to variations in the characteristic crustal structure of the region, constrained by the receiver perturbation, and errors in origin time and/or focal depth, determined from the source perturbation. The estimates of perturbation functions therefore suggest systematic regional biases in crustal structure and hypocentral parameters. A less than average crustal thickness in oceanic regions and greater thickness in stable continental regions is indicated. Furthermore, it appears that the origin times of sources in oceanic regions are systematically determined too late and/or focal depths located too shallow, whereas origin times of sources in continental regions are systematically determined too early and/or focal depths located too deep.