bluuebunny/crossref_metadata_2025 huggingface dataset:
Intraradicular rehabilitation of a necrotic, immature tooth using MTA, a fiber post and composite resin - A case report
Authors: Naicker Deon , Tootla Saidah
Published: September 2021

Endodontic treatment of necrotic, immature teeth with open apices can present challenges to debridement, disinfection, and optimal obturation. These teeth may have widely flared canals and thin radicular dentinal walls that are susceptible to fracture. Management of the open apex can be performed using a mineral trioxide aggregate (MTA) apical plug. To ensure a better prognosis in such structurally compromised teeth, internal radicular reinforcement using fiber posts and a self-adhesive cement has been suggested. The present case report illustrates the management of a necrotic, immature maxillary right central incisor in a 10-year-old patient using the MTA apical barrier technique and canal reinforcement using a fiber post.
Percursos da Formação Inicial em Pedagogia na legislação brasileira: desafios para a docência na Educação Infantil
Authors: Côco Valdete , De Andrade Vieira Maria Nilceia , De Fátima Giesen Karina , Côco Dilza
Published: September 2021

Numa perspectiva histórica da Pedagogia e em vinculação com o direito à educação, este artigo analisa as premissas estabelecidas para a Formação Inicial de professores para a docência, na Educação Infantil no contexto das transformações que marcam as atuais políticas públicas educacionais brasileiras. Baseado em referenciais teórico-metodológicos de Mikhail Bakhtin, este texto decorre de uma pesquisa de abordagem qualitativa e de cunho bibliográfico, desenvolvida por meio de análise documental da legislação educacional brasileira, com destaque para a vigência da Lei 13.005/2014, que institui o Plano Nacional de Educação, da Resolução 01/2006, que estabelece as Diretrizes Curriculares Nacionais para o curso de graduação em Pedagogia, e da Resolução 02/2015, que define as Diretrizes Curriculares Nacionais para a Formação Inicial em nível superior assim como para a formação continuada. Considerando a pertinência na produção de políticas públicas, os documentos reúnem concepções que se vinculam a diferentes contextos sócio-históricos, evidenciando diversas (por vezes, divergentes) perspectivas e interpretações, dirigidas aos processos formativos dos docentes e ao trabalho educativo com as crianças. As análises efetuadas indicam problematizações referentes à organização curricular, à dinâmica das ações e às interfaces com o campo de trabalho, por isso assinalam que os ordenamentos legais se efetivam em meio a disputas e tensões. Ainda assim, elas atestam a formação em nível superior como uma conquista e enfatizam a relevância do cumprimento das metas e estratégias do Plano Nacional de Educação no horizonte da defesa do direito das crianças pequenas à educação de qualidade socialmente referenciada.
Müşteri Deneyimi, Müşteri Tatmini ve Müşteri Sadakati Arasındaki İlişkinin İncelenmesi: Hazır Giyim Sektöründe Bir Araştırma
Authors: ÇAVUŞOĞLU Sinan , DEMİRAĞ Bülent
Published: September 2021

Araştırma giyim mağazalarını ziyaret eden tüketicilerin edinmiş oldukları deneyimin; müşteri tatmini ve sadakati üzerindeki etkisinin belirlenmesi amacıyla gerçekleştirilmiştir. Araştırmanın evrenini giyim üzerine tüketim yapan ve sıklıkla benzer giyim mağazalarını ziyaret eden tüketiciler oluşturmaktadır. Araştırmada hipotezlerin test edilmesi için Smart PLS 3 (Partial Least Squares) istatistik programı kullanılmıştır. Araştırmada ölçülmesi amaçlanan hipotezlerin testi için bootstrapping tekniği uygulanmıştır. Analiz sonuçlarına göre müşteri deneyiminin duyusal, duygusal, düşünsel ve ilişkisel boyutlarının müşteri tatmini ile istatistiksel olarak anlamlı bir ilişkiye sahip olduğu belirlenmiştir. Ayrıca müşteri deneyiminin duyusal, duygusal, düşünsel ve davranışsal boyutlarının müşteri sadakati ile benzer şekilde istatistiksel olarak anlamlı bir ilişkiye sahip olduğu tespit edilmiştir. Yapılan analizler neticesinde davranışsal boyutun müşteri tatminini; ilişkisel boyutun ise müşteri sadakatini etkilemediği sonucuna ulaşılmıştır.
Comportamiento discursivo del enunciado “territorio ancestral” en las sentencias de la Corte Constitucional de Colombia
Authors: Barbosa Becerra Joice Johanna María
Published: September 2021

La hegemonía discursiva ha imposibilitado a los pueblos indígenas expresarse en sus propios términos, sin embargo, en el ejercicio inacabado de las disputas por el poder decir, se han visto condicionados a entrar en las luchas del campo jurídico que, aun imponiendo reglas ajenas a sus prácticas culturales, políticas y del derecho propio, se constituyen en una estrategia para la ampliación y garantías de sus derechos humanos. En este artículo, se presenta parte de los resultados del análisis crítico del discurso de las sentencias de la Corte Constitucional colombiana, que fallaron a favor de la Consulta Previa, libre e informada, específicamente el análisis del comportamiento discursivo del enunciado “territorio ancestral”. Las disputas por el poder decir, de los pueblos indígenas y una Corte con enfoque de derechos, han procurado, paulatinamente, permear de ancestralidad los discursos duros del campo jurídico. Sin embargo, aunque la Corte resolvió otorgar el amparo del derecho de consulta previa, en el seguimiento a los casos se encontró que las consultas no fueron llevadas a cabo y, en su mayoría, hubo una profundización de las problemáticas que se intentaban resolver, debido a que las causas de la conflictividad territorial permanecen intactas.
Aspectos psicosociales y condiciones educativas de docentes de lengua en formación durante el confinamiento por la pandemia de COVID-19
Authors: García Botero Jacqueline , García Botero Gustavo , Botero Restrepo Margarita Alexandra
Published: September 2021

Dada la contingencia sanitaria mundial a causa de la covid-19, los escenarios educativos en todo el mundo se convirtieron en “laboratorios investigativos”, en los cuales cobraron gran importancia los procesos de enseñanza-aprendizaje mediados por la tecnología. Por esto, la presente investigación tuvo como objetivo principal identificar los aspectos psicosociales y las condiciones educativas que influyeron en la satisfacción con el aprendizaje de 423 estudiantes pertenecientes a un programa de Licenciatura en Lenguas Modernas con énfasis en Inglés y Francés de una Universidad en Colombia que empleó la metodología de presencialidad asistida por la tecnología (pat). Para esto, se implementaron cuestionarios abiertos, grupos focales y observaciones participativas, los cuales fueron analizados siguiendo las etapas del análisis de datos cualitativos planteadas por Miles et al. (2014) y los procesos de codificación propuestos por McCracken (1988). Se concluyó que las categorías determinantes que inciden en la satisfacción del estudiante son el apoyo del profesor y las condiciones estructurales. Estas dos categorías tienen un impacto en otros aspectos psicosociales que se convierten en un desafío para la metodología pat. Los resultados señalan la necesidad de una reflexión pedagógica que ayude a unificar criterios para una implementación apropiada de esta metodología.
Malaysian English Language Teachers’ Agency in Using Digital Technologies During the Pandemic: A Narrative Inquiry
Authors: Zainal Azlin Zaiti , Zainuddin Siti Zaidah
Published: September 2021

With the closure of schools due to imposed lockdowns in many parts of the world, teachers had to make a rapid transition from teaching in physical classrooms to online teaching, even though they had little to no experience teaching online prior to the pandemic. Adopting a narrative inquiry approach, this study aimsto explore the factors that influence Malaysian English language teachers’ professional agency in adapting to online teaching. Data were collected via interviews with ten secondary school teachers from rural and urban schools. The findings show how factors such as teachers’ perceptions of the affordances of digital tools and existing support structures influence teachers’ enactment of agency in online teaching and learning. They also demonstrate teachers' agentic potential to adapt their lessons to suit their learners’ needs. These findings suggest the need for teacher professional development programs to recognize teacher agency in the design of future training modules. This involves providing a differentiated training curriculum that can support and sustain language teachers’ development organically by taking into consideration their existing technology skills, teaching experiences and work contexts.
“A Stressful Unknown” or “an Oasis”?: Undergraduate Students’ Perceptions of Assessment in an In-Class and Online English Phonetics Course
Authors: Czura Anna , Baran-Łucarz Małgorzata
Published: September 2021

The sudden need to switch from traditional in-class instruction to online teaching and assessment due to the covid-19 pandemic has posed considerable challenges to teachers, but also to learners. The mixed method study reported in this article compared Polish undergraduate students’ cognitive, affective, and behavioural responses to assessment provided in two practical English phonetics courses taught during an in-class fall semester and online spring semester. The quantitative data were collected by means of an online questionnaire, which consisted of three categories of semantic differential scales referring to the cognitive, affective, and behavioural responses. The qualitative data consisted of drawings, open-ended surveys, and individual interviews with the students. The t-test results showed significant differences in students’ perceptions in terms of cognitive and behavioural aspects. The qualitative data revealed that although the students highly valued formative assessment in the course, the online mode weakened their engagement and interest in receiving feedback. It was also observed that students’ perceptions of in-class and online assessment were shaped largely by their individual differences and learning preferences. The study underlies the importance of using anxiety-lowering techniques in both in-class and online classes, and the need for fostering undergraduate students’ autonomous learning skills.
Enseñanza virtual de lengua inglesa durante el confinamiento domiciliario: percepciones y reacciones del alumnado en una universidad española
Authors: Echauri Galván Bruno , García Hernández Silvia , Fernández-Gil María Jesús
Published: September 2021

La explosión de la pandemia de covid-19 en España supuso un reto mayúsculo para las universidades con educación presencial ya que estas fueron obligadas a adaptarse a la docencia en línea de manera casi inmediata. Este artículo tiene el objetivo de ofrecer una instantánea de los resultados de este salto repentino a un modelo virtual en la enseñanza de lengua inglesa en distintos programas de grado de la Universidad de Alcalá en España. Para ello, se centra en las percepciones y reacciones del alumnado. Los datos derivaron de una encuesta respondida por 159 estudiantes de Inglés de las facultades de Filosofía y Letras; y de Ciencias Económicas, Empresariales y Turismo, y de un grupo de discusión posterior en el que participaron los autores del estudio y una selección de los encuestados. Estos dos métodos se utilizaron para ahondar en el tratamiento dado a aspectos centrales de la enseñanza de lenguas extranjeras, tales como: (a) la adquisición de competencias, (b) los métodos de evaluación, (c) la utilidad de las tecnologías de la información y la comunicación (tic), y (d) la interacción entre estudiantes y entre estudiantes y docentes, durante el periodo de enseñanza a distancia que sobrevino a la pandemia. Los resultados evidenciaron la problemática que entraña esta modalidad virtual en cuanto a la adquisición y la práctica de destrezas como la expresión oral, la participación en clase, la articulación del trabajo en grupo y las relaciones interpersonales. Además, subrayaron beneficios, tales como un mayor conocimiento y manejo de los recursos tecnológicos. Finalmente, sirvieron para mostrar al profesorado los instrumentos digitales de trabajo y evaluación mejor y peor valorados por el estudiantado.
Condylar position changes after three months of treatment with posterior bite turbo
Authors: Herrera-Guardiola Santiago , Puerta-Salazar German Eduardo , Martínez-Cajas Carlos Humberto
Published: September 2021

Introduction: all orthodontic treatments must be safe in terms of temporomandibular joint health. No reports in the recent literature evaluate the association between the use of posterior bite turbos and condylar position changes. The aim of the present study was to evaluate condylar position changes occurring after three-month treatment with posterior bite turbo in patients from the Dental School of the Universidad del Valle. Methods: a sample of 15 hyperdivergent patients was randomly distributed into two groups: Bite Turbo and Control Group. Cone-Beam Computed Tomography (CB-CT) was used to assess the condyle position before the bite turbos bonding to first and second molars, and after three months of use of the appliances. Distances were taken from the CB-CT by a single operator, and the calibration was tested with intraclass correlation (> 0.9). Results: no statistical difference between the position of left and right condyles was detected. However, there was a significant difference in the upper space of the left condyle between the initial and final measurement. Patients reported satisfactory use of the occlusal bite turbo (85.8%) in three months of treatment. Conclusion: contrary to the expected, the simultaneous use of posterior occlusal appliances with balanced mandibular movements for 3 months did not cause significant changes in condylar position. The patients tolerate well the use of occlusal stops.
A Vulpia ciliata morfológiája és magyarországi terjedésének sikere a vasúthálózat mentén
Authors: Mesterházy Attila , Wirth Tamás , Schmidt Dávid , Csiky János
Published: September 2021

A Mediterráneumban elterjedt Vulpia ciliata Dumort Európa több országában, jellem­zően vasutak mentén jelent meg az elmúlt évtizedekben. A fajt 2016 tavaszán észleltük először Ma­gyarországon, a szolnoki vasútállomáson, majd néhány nappal később Budapest-Keleti pályaudvaron. A faj 2020-ban számos más dunántúli vasútállomáson is megtaláltuk, és úgy tűnik, hogy napjainkra az ország jelentős részén megtelepedett. A V. ciliata ezidáig csak a rendszeresen használt vágányok köze­léből (max. 20 m-es távolságon belül) került elő, feltehetően a vasúti áruszállítással jutott be az ország­ba, és terjedt el. A faj nálunk már meghonosodottnak tekinthető, özönfajként egyelőre még csak a vasút menti ruderális vegetációban lép fel, ahol az őshonos Vulpia myuros-t ki is szoríthatja. A faj a szőrös toklászai alapján a hasonló termőhelyen gyakori V. myuros-tól egyértelműen megkülönböztethető. Virágzása a két másik fajnál korábban, gyakran már áprilisban elkezdődik. A vizsgált morfológiai jelle­gek alapján (padkák száma a buga csúcsának 2 cm-es szakaszán, termések száma/füzérke, fertilis virá­gok aránya/füzérke, alsó és felső pelyvahossz, toklász- és szálkahossz, buga főtengelyének vastagsága a csúcsi 2 cm-es szakaszon) megállapítható, hogy a V. bromoides és V. myuros kevésbé különbözik egy­mástól, mint a V. ciliata e két fajtól. Feltételezhető továbbá, hogy a füzérkén belüli alacsony fertilitási arány, a toklászok pillássága összefüggésbe hozható a faj terjedési sikerével (csoportos terjedés, anemochória, zoochória, antropochória). Korai (májusi) termésérése is kedvez a vasút menti terjedés­nek, ui. így a többi hasonló fajjal szemben már terméses állapotban vészelheti át a késő tavasszal kez­dődő gyomirtást. A vasúthálózaton kívüli magyarországi terjedését egyelőre akadályozhatják a klimati­kus viszonyok, illetve a pályatesteken kívüli, relatív előnyt kínáló szezonális gyomirtások hiánya.
Ensemble Learning based Age Invariant Fea-ture Recognition Using Soft Computing
Authors: Dr. Bhavesh Chauhan Divyanshu Sinha, Dr J. P. Pandey,
Published: September 2021

Face recognition system is a state-of-the-art computer vision application within the artificial intelligence arena. Face recognition is the automated recognition of humans for their names/unique ID. The age invariant face recognition is a challenge task in the field of face recog-nition. In this work, we have introduced a stacked support vector machine where kernel activation of prototype examples is combined in nonlinear ways. The proposed work integrates soft compu-ting-based support vector machine (SVM) with deep SVM. The proposed model uses the implied relation between the variables described above in order to optimize their overall performance. Specifically, our method uses three different stages of complex convolution neural networks that detect and analyze the location of faces position and landmarks. This work has introduced cross-age celebrity dataset (CACD) for both single as well as cross-database enabling the transition of age. The proposed work has been implemented in the MATLAB simulation tool considering CACD dataset. Experimental results indicate that our techniques significantly outperform other strategies across a range of challenging metrics.
The “shadow” from a velocity reversal
Authors: Hron M. , Chapman C. H.
Published: September 2021

abstract

The “shadow” from an Epstein “sech2” profile is caused by exponential decay of amplitude. The decay constant, which is independent of frequency, is identical with that obtained from the classical ray theory. The spectral amplitudes and theoretical seismograms evaluated numerically show the effect of the reversal on the acoustic wave propagation.
Torsional overtone dispersion from correlations of S waves to SS waves
Authors: Brune James N. , Gilbert Freeman
Published: September 2021

abstract

This paper presents SH overtone dispersion data obtained by using the phase correlation method of Brune (1964). The data augment the set provided by longer-period spheroidal and toroidal mode data and travel-time data. A major advantage of the phase-correlation method over travel-time data is the elimination, to first order, of source effects and source-region bias. The overtone data are consistent with lower-order spheroidal overtone data indicating a base-line correction of 4.0 ± 0.9 sec to the S-wave travel-time data of Hales and Roberts (1970). These and other fundamental-mode and overtone data, travel-time data, and mass and moment of inertia comprise 497 gross earth data and represent one more step in the march toward a spherically averaged earth model.
Stability of P an S velocities from Central California quarry blasts
Authors: McEvilly T. V. , Johnson L. R.
Published: September 2021

abstract

Travel times of crustal P and S waves from 70 quarry blasts in Central California between July 1961 and June 1973 have been measured for seven paths 46 to 168 km long passing in several cases within 10 km of hypocenters of moderate (ML 4.5 to 5.4) earthquakes. All P and S times and their ratios TS/TP lie within 2.3 per cent of the mean values and over 97 per cent of the TS/TP ratios lie within 1 per cent of the mean values. Variations can be explained by reading errors and uncertainties in source times and locations. There are no indications of velocity variations related to earthquake occurrences. Mean VP/VS ratios range from 1.73 to 1.84 for the various paths. The phenomenon of premonitory dilatancy accompanied by a 10 to 20 per cent reduction in VP or VP/VS cannot be reconciled with these observations unless the affected source regions have lateral dimensions less than about 5 km for these moderate strike-slip earthquakes.
Upper mantle shear-wave velocity structure in the Japan region
Authors: Kaila K. L. , Krishna V. G. , Narain Hari
Published: September 2021

abstract

The upper mantle shear-wave velocity structure in the Japan region has been determined from S travel times of 101 earthquakes with focal depths varying from 40 to 600 km, using a new analytical method given by Kaila (1969). In southwestern Japan, the S velocity obtained as 4.35 km/sec at a 40-km depth remains almost constant to a depth of about 170 km. The shear velocity in northeastern Japan increases linearly from 4.42 km/sec at a depth of 45 km to 4.62 km/sec at a depth of 145-km. For central Japan, the S velocity determined as 4.41 km/sec at a 40-km depth increases linearly to 4.55 km/sec at a 170-km depth, followed by a slight decrease in the velocity gradient, with velocity still increasing linearly to 4.68 km/sec at a depth of 345 km. At this transition depth, there is a first-order velocity discontinuity, the velocity increasing from 4.68 to 4.92 km/sec. Below this depth, velocity again increases linearly from 4.92 to 5.04 km/sec at a depth of 600 km. The shear velocities at depths between 440 to 640 km in Japan are found to be extremely low in comparison to those of Jeffreys (1939), Gutenberg (1959), and Arnold (1967). These low S velocities can explain satisfactorily the late S arrivals from shallow earthquakes between Δ = 20° to 30° as observed in the Japanese region. Graphs have been drawn to show the variation with depth of Δ*, the epicentral distance to the inflection point, Δ1, Δ2, (Δ2 − Δ1), ptrue =∂T/∂Δ, and αS = (T − pΔ) at the inflection point as obtained from the S-wave travel-time analysis.
Seismic investigation of a san francisco bay mud site
Authors: Warrick Richard E.
Published: September 2021

abstract

Measurements were made of the shear- and compressional-wave velocities necessary to determine the seismic response of a site on the edge of the San Francisco Bay, California. The shear wave is the most difficult to isolate because of the complications of earlier arriving energy. Downhole and surface measurements yielded shear-wave velocities of 90 to 130 m/sec and compressional-wave velocities of 1,400 m/sec for soft mud. The underlying older sediments had interval shear-wave velocities of 270 to 380 m/sec, increasing with depth. The corresponding P velocities for the older sediments were 1,600 to 1,840 m/sec. The horizontal traction technique of shear-wave generation proved to be the most successful of the methods tested.
Seismicity of the Middle America arc-trench system near Managua, Nicaragua
Authors: Dewey James W. , Algermissen S. T.
Published: September 2021

Hypocenters of earthquakes occurring during the period 1950 through 1972 in the Middle America arc-trench system near Managua, Nicaragua, have been relocated by the method of joint hypocenter determination (JHD) or the master event method with the Managua earthquake of December 23, 1972 as the calibration event. The relocated hypocenters show a considerably narrower Benioff zone than previous hypocenters of the same earthquakes and clearly separate shallow-focus volcanic terrane earthquakes of the type which struck Managua from the Benioff zone earthquakes. The shallow-focus volcanic terrane earthquakes are probably caused by tectonic conditions associated with the formation of the Nicaraguan depression or the principal chain of Quaternary volcanoes. The Managua earthquake of December 23, 1972 may have occurred as a consequence of slippage along a transform fault zone which connects offset segments of the chain of Quaternary volcanoes; the volcanic chain is then taken to be the surface expression of a secondary spreading zone which lies above the Benioff zone of the Middle America arc-trench system. Alternatively, the recent Managua earthquake may have occurred as a consequence of regional east-west tension in the Nicaraguan depression.
Seismic source and transmission functions from underground nuclear explosions
Authors: Dahlman Ola
Published: September 2021

abstract

A model is presented for the simultaneous detemination of the relative variation in transmission properties to different stations and of the relative differences between the seismic sources for closely spaced underground nuclear explosions recorded by a fixed seismological station network. The model is applied to short-period data reported from 24 globally distributed stations from 12 underground nuclear explosions with known yields at Nevada Test Site. The obtained transmission functions vary within a factor of 10 between the different stations and show a weak decrease with epicenter distance and little correlation with the Gutenberg amplitude-distance curve. The relative source functions for 10 explosions in tuff and rhyolite, with yields in the range 16 to 1,200 kt, are with good correlation proportional to explosion yield to 0.9. Two theoretical source-function models, one by Haskell (1967) and one by Mueller and Murphy (1971a), are compared with each other and they agree well for frequencies around 1 Hz and for yields in the range 3 to 300 kt. The Haskell model for tuff is modified to be more compatible with the models for salt, granite and alluvium. The Haskell model predicts stronger variation of the source functions with frequency and yield than the Mueller-Murphy model. The observed relative source functions are compared with the theoretical source functions obtained from the two source models. The agreement is fairly good but the relative decrease of the source functions at yields above 300 kt predicted by the theoretical models is not observed.
Time functions appropriate for deep earthquakes
Authors: Burdick L. J. , Helmberger D. V.
Published: September 2021

The seismic signatures of isolated body phases from many deep-focus earthquakes were analyzed in the time domain. Most shocks were found to be multiple events when examined in detail. The time history derived from P waves for single events predict synthetic S-wave shapes that match the observations, indicating compatibility with shear dislocation theory. Several other features of source functions in the time domain have been brought to light.
Dilatancy and spatial distribution of aftershocks
Authors: Gupta Indra N.
Published: September 2021

abstract

The pre-earthquake dilatancy, postulated to explain certain premonitory seismic velocity changes, may provide a preferred direction of groundwater flow persisting after the occurrence of a shallow earthquake. This direction is parallel to and nearly coincident with the compressive stress axis associated with the focal mechanism of the principal shock. Aftershocks may result from a redistribution of pore pressure and fluid flow not only along faults but also along this direction of relatively large permeability. This suggestion provides a possible explanation for certain observations of aftershocks aligned along the compressive stress direction.
First strong-motion instrumentation in Hawaii: With results from the earthquake of April 26, 1973
Authors: Adams W. M.
Published: September 2021

abstract

On April 26, 1973, an earthquake with magnitude of 614 occurred at a depth of 40 km below Honomu (north of Hilo). Serendipitously, in the preceding February, one SMA-1 accelerograph and one Wilmot seismoscope were installed near Waikiki on the island of Oahu. Also, one SMA-1 accelerograph and three Wilmot seismoscopes were installed on the island of Hawaii. The records from these instruments provided the first strong-motion data for the State of Hawaii. The motion was dominantly horizontal. This finding explains the extensive damage to the Hilo area, reported to be about 6 million dollars.
Definition and identification of seismic events in the USSR in 1971
Authors: Dahlman Ola , Israelson Hans , Austegard Atle , Hörnström Gunnel
Published: September 2021

abstract

Seismic events reported to have occurred in the USSR in 1971 are studied to assess the seismic monitoring problem as it may occur in the context of a complete test-ban treaty. Available epicenter data of a total of 199 events, 180 earthquakes and 19 explosions, are presented. Focal depth estimates reported by the National Oceanic and Atmospheric Administration, U.S., and the Institute of Physics of the Earth, Moscow, are compared. Identification parameters determined using short- and long-period data from Hagfors Observatory and supplementary short-period data from the Yellowknife array station in Canada are presented. To study the combined operative efficiency and applicability of available identification parameters, the reported depth estimates and the identification data are assessed in a defined way.
Time functions appropriate for some aftershocks of the point Mugu, California earthquake of February 21, 1973
Authors: King David , Helmberger Donald V.
Published: September 2021

abstract

Broad-band recordings of aftershocks of the Pt. Mugu earthquake at small epicentral distances provided an excellent opportunity to test source models for small earthquakes. Simple events recorded at nearly vertical incidence produced a single P-wave pulse of a duration of about 0.07 sec and a somewhat more complicated S wave with a slightly longer duration. Such events are consistent with a point dislocation source for which Qβ = 100 or for which there is directivity with the fault breaking downward. We attribute the more usual complexities of small earthquake records to multiple events, some of which we observed, layering effects combined with greater epicentral distances, and scattering.
Conversion of Sn to Lg at a continental margin
Authors: Isacks Bryan L. , Stephens Christopher
Published: September 2021

abstract

Examination of the seismic phase Sn from earthquakes in the West Indies as recorded by numerous stations in eastern North America reveals that a substantial fraction of the short-period energy carried by Sn across the suboceanic lithosphere of the Atlantic is fed into the continental crust near the continental margin and travels into North America as the crustal phase Lg. As distance within the continent increases, the Lg part of the short-period wave train becomes predominant, and can be identified at stations in northern Canada as far as 58° from the sources. Several estimates of the average Q for the attenuation of Lg in eastern North America agree upon values in the range of 600 to 1,400. Hydrophone recordings at Bermuda indicate an average Q as high as 4,000 for the attenuation of Sn in the suboceanic lithosphere. Conversion of Sn to Lg also appears to occur near the margin between the continental U.S. and the Gulf of Mexico. In this case, Sn travels northward across the Gulf from earthquakes located near the border between Mexico and Guatemala.
Some autoregressive models for short-period seismic noise
Authors: Tjøstheim D.
Published: September 2021

abstract

It is shown that short-period seismic noise at the NORSAR seismic array can be described by a parametric model having the form X ( t ) − a 1 ( t ) X ( t − 1 ) − … − a p ( t ) X ( t − p ) = Z ( t ) where X(t) is used to denote the noise process. This is a nonstationary generalization of the standard autoregressive models allowing time-varying autoregressive coefficients and a nonstationary white-noise residual process Z(t). The coefficients a1(t), a2(t), …ap(t) and the residual variance σ2z(t) are estimated using data from the NORSAR seismic array. It is found that the short-period noise at NORSAR is quite satisfactorily described by a third-order (p = 3) model. Also, it is found that the nonstationary character of the noise is due primarily to time variations of the residual variance and the lower order autoregressive coefficients.
The thin sedimentary layer of the Sonoran Embayment
Authors: Wilhelm R. , McIntyre R. G. , Slusher H. S.
Published: September 2021

abstract

Five earthquakes from the Gulf of California, recorded at the John W. Kidd Memorial Seismological Observatory of The University of Texas at El Paso, are analyzed to estimate the thickness of the sedimentary layer of the Sonoran Embayment located southwest of El Paso, Texas and bounded on the western extremity by the Sierra Madre Occidental. The seismograms are digitized at 12-sec intervals and filtered in the time domain with a Parzen lag window to regenerate the fundamental-mode Rayleigh waves. Arrival times of these short-period surface waves are reduced to the time required to propagate through the Sonoran Embayment. The data are studied by Savarensky's method and by spectral analysis to yield group-velocity dispersion values. The results of the two distinct methods agree well. Theoretically obtained dispersion curves, in which the indexing parameter is layer thickness, are fitted to the velocity dispersion points. It is found that the sedimentary layer of the Sonoran Embayment is 2 to 3 km thick.
Statistical analysis of microearthquake activity near San Andreas geophysical observatory, Hollister, California
Authors: Udias Agustin , Rice John
Published: September 2021

Microearthquake activity during the 4-year interval 1968 to 1971 in a region of 25 km radius, centered on the San Andreas fault near Hollister, has been monitored by means of high-gain high-frequency seismographs which allow detection of events as small as magnitude zero within the region. The distribution of the 4764 microearthquakes shows a high degree of clustering. The series of time intervals between consecutive shocks can be described approximately by a gamma distribution whose shape parameters for different samples change from 0.3 to 0.8. The exponential probability plots of the {Δti} series for 265 larger regional earthquakes over 10 years result in a constant value of the hazard function except for small values of time where the hazard is higher. The variance-time and intensity functions show a varying degree of interdependence between events for each year and a long-term dependence up to 80 days for the period 1968-1971. The time scale of clustering has been estimated. Inferences based on short-term microearthquake studies may be grossly misleading.
Details of microearthquake swarms in the Columbia basin, Washington
Authors: Malone Stephen D. , Rothe George H. , Smith Stewart W.
Published: September 2021

Three microearthquake swarms in the Columbia River basin of eastern Washington have been studied by means of a small portable seismic network. Earthquakes in this area typically occur in swarms, concentrated both temporally and spatially. One unusual characteristic of the three swarms studied was the shallow focal depths of all events. Most events located had depths less than 1 km; none were deeper than 2 km. Composite focal mechanism solutions indicate that more than one fault surface is active in any one swarm. All events had some thrust component with the axis of maximum compression oriented roughly in a north-south direction.
P-wave amplitude variation with epicentral distance and the magnitude relations
Authors: Kaila K. L. , Sarkar Dipankar
Published: September 2021

Investigation of the variation of P-wave amplitudes and d2T/dΔ2 with epicentral distance reveals that the amplitudes in the distance range up to 100° can be represented by seven discontinuous curves. The discontinuous nature of the amplitude curves can be explained due to the possible existence of first- or second-order velocity discontinuities in the upper and lower mantle of the Earth. Seven magnitude relations corresponding to these amplitude curves are given, which yield consistent magnitudes for nuclear explosions as well as for shallow earthquakes.
Earthquake precursors
Authors: Rikitake Tsuneji
Published: September 2021

An analysis of existing earthquake precursor data leads to a conclusion that the precursors reported so far can be classified into three types, i.e., A1, A2 and B types. Most of type B precursors, observed in terms of anomalous tilts and strains or foreshocks, have no magnitude-dependent precursor time. Meanwhile the A2-type precursors observed by means of geodetic work, changes in seismic-wave velocities and the like seem to have a precursor time which is closely correlated to the magnitude of coming earthquakes. A precursor of this type may possibly be interpreted by the current theory of dilatancy. The A1-type precursors, observed mostly several hours prior to the main shock, may be caused by a creep-like failure before the main rupture of the Earth's crust.

Probabilities for an anomalous signal of various geophysical elements to be related to a forthcoming earthquake are estimated on the basis of the existing data of precursors.

A feasible strategy for predicting a large earthquake as suggested by the present study will be as follows: First of all, we monitor accumulation of crustal strain by means of geodetic work. The next task is to detect an A2 signal which would arise from a highly strained crust sooner or later. If the spatial extent of the A2-type precursor is known, it is possible to estimate roughly the magnitude as well as the occurrence time of the coming earthquake. Finally, detection of an A1-type precursor, if it should occur, would provide a short-range forecast having a time span of hours.
Diffraction of Love waves by perfectly rigid and perfectly weak half-planes
Authors: Kazi M. H.
Published: September 2021

In this paper we investigate the transmission and reflection of Love waves, normally incident on a perfectly rigid half-plane or a perfectly weak half-plane, which lies in a layer of uniform thickness, overlying a semi-infinite solid. The half-plane is parallel to the interface of the two materials and lies in the upper layer. The perfectly rigid half-plane is a domain of vanishing displacement, whereas the perfectly weak half-plane is a domain of vanishing traction. We use the Wiener-Hopf technique based on an approach due to D. S. Jones (1952). Such a method has previously been employed by R. Sato (1961) in his paper on Love waves incident on a change of thickness in the surface layer.

We set up the two boundary value problems, and obtain analytical solutions for transmitted and reflected Love and channel waves in the case of the rigid as well as the weak screen. We draw the following conclusions:

Finally, we show the connection between the problem of Love waves past a weak screen and Sato's problem of Love waves incident on a vertical step discontinuity in the surface layer, from the thicker to the thinner side.
Seismic waves in a wedge
Authors: Alterman Z. , Nathaniel R.
Published: September 2021

abstract

The equations for elastic-wave propagation caused by an explosive point source are solved, by a finite difference scheme, for the case of an elastic wedge, with free boundary.

Varying the wedge angle shows that the amplitude of the motion, at the corner, increases as the wedge angle is decreased. The results indicate that for wedges with angles varying from 0° to 180°, the amplitude decreases with decreasing β/α (shear- to compressional-wave velocity). The corner of the wedge generates surface waves and the elliptical particle motion in the waves is analyzed. The particle motion is elliptic and the major axes of the ellipses are inclined at half the wedge angle to the free surface.

The surface wave travels to the corner from where it is “transmitted” and reflected.

Surface waves are shifted by 180° - θ after transmission.

For the case of a quarter plane, we get the same result as Alterman and Loewenthal (1970).
Rayleigh waves from high-gain long-period stations: Signal extraction, amplitude determination, and separation of overlapping wave trains
Authors: Berg Eduard
Published: September 2021

abstract

For a signal-to-noise ratio between 0.2 and 0.1 on the original single-component records, amplitudes for Rayleigh waves over oceanic paths of 155° at station MAT and 98° at station KIP have been determined as 12 mμ and 24 mμ peak-to-peak, respectively, with a standard error of less than 11 per cent. In each case the processed correlation signal is the highest in a half-hour record. The method makes use of preliminary high-pass filtering and normalized reference earthquake-matched filtering, and takes full advantage of the well-dispersed oceanic surface wave.

The method also provides high resolution of co-located events with short time separation, or of widely spaced events with Rayleigh waves arriving nearly simultaneously at a single station, when the summed vertical and radial matched filtered components are used. Examples include: (1) clear separation and amplitude determination at stations KIP and MAT of two MS = 6.5 earthquakes located 0.7° and 145 sec apart off the coast of central Chile; (2) clear separation at station KIP of a Novaya Zemlya mb = 4.8 event from interfering Rayleigh waves of an mb = 5.0 Kermadec Island earthquake arriving 120 to 140 sec prior to the searched event, with almost complete elimination of interference on the summed vertical and radial processed components; and (3) clear separation at station KIP of two co-located mb = 4.4 and 4.5 earthquakes 6 min apart off the coast of Chile, with determination of their amplitudes in the presence of interfering Rayleigh waves from two central Alaska earthquakes, the first (mb = 4.1) arriving 15 min prior to the first Chile Rayleigh wave and the second between the two Chile arrivals.

The single-station threshold reached (10 and 25 digital units, p-p) for stations MAT and KIP at 155° and 98°, respectively, corresponds to an MS = 3.3 and probably can be improved further.
Dependence of magnitude statistics on strain rate
Authors: McGarr A.
Published: September 2021

Magnitude statistics (log N = a − bM) were measured for mine tremors and for the Parkfield earthquakes, listed by McEvilly, Bakun and Casaday (1967), in conditions of varying rates of aseismic ground deformation. Aseismic deformation rates were estimated using a tiltmeter in the ERPM gold mine and using results from small geodetic networks, reported by Smith and Wyss, for the region near Parkfield, California. In the magnitude-frequency relationship, b is independent of the rate of aseismic deformation, ε˙,anda=logε˙+Κ, where K is a constant. Thus, the level of seismicity appears to be determined by the rate of aseismic ground deformation. Changes in shear stress of the order of 100 bars do not have any measurable effect on the magnitude statistics.
Microtremor analysis of local geological conditions
Authors: Katz Lewis J.
Published: September 2021

abstract

The application of microtremor spectra in predicting frequency-dependent amplification effects of local site geology was investigated. Long time-interval (> 45 min) microtremor data were used to estimate Power Spectral Density (PSD) plots. Peaks occurring in these PSD plots were correlated with peaks of transfer functions (Haskell, 1960 and 1962) calculated from known geological models. The resulting apparent positive correlations indicate that a procedure of estimating PSD plots from long time intervals of microtremor data would be useful in predicting response spectra for earthquake risk evaluation.
Effects of local geological conditions in the San Francisco Bay region on ground motions and the intensities of the 1906 earthquake
Authors: Borcherdt Roger D. , Gibbs James F.
Published: September 2021

abstract

Measurements of ground motion generated by nuclear explosions in Nevada have been completed for 99 locations in the San Francisco Bay region, California. The recordings show marked amplitude variations in the frequency band 0.25 to 3.0 Hz that are consistently related to the local geological conditions of the recording site. The average spectral amplifications observed for vertical and horizontal ground motions are, respectively: (1, 1) for granite, (1.5, 1.6) for the Franciscan Formation, (3.0, 2.7) for the Santa Clara Formation, (3.3, 4.4) for alluvium, and (3.7, 11.3) for bay mud. Spectral amplification curves define predominant ground frequencies in the band 0.25 to 3.0 E for bay mud sites and for some alluvial sites. Amplitude spectra computed from recordings of seismic background noise at 50 sites do not generally define predominant ground frequencies.

The intensities ascribed to various sites in the San Francisco Bay region for the California earthquake of April 18, 1906, are strongly dependent on distance from the zone of surface faulting and the geological character of the ground. Considering only those sites (approximately one square city block in size) for which there is good evidence for the degree of ascribed intensity, the intensities for 917 sites on Franciscan rocks generally decrease with the logarithm of distance as

Intensity = 2 . 6 9 - 1 . 9 0 log ( Distance in kilometers ) . ( 1 )

For sites on other geological units, intensity increments, derived from this empirical relation, correlate strongly with the Average Horizontal Spectral Amplifications (AHSA) according to the empirical relation

Intensity Increment = 0 . 2 7 + 2 . 7 0 log ( AHSA ) . ( 2 )

Average intensity increments predicted for the various geological units are −0.3 for granite, 0.2 for the Franciscan Formation, 0.6 for the Great Valley sequence, 0.8 for the Santa Clara Formation, 1.3 for alluvium, and 2.4 for bay mud. The maximum intensity map predicted on the basis of these data delineates areas in the San Francisco Bay region of potentially high intensity for large earthquakes on either the San Andreas fault or the Hayward fault. The map provides a crude form of seismic zonation for the region and may be useful for certain general types of land-use zonation.
Study of seismological evasion
Authors: Evernden Jack F.
Published: September 2021

abstract

This paper discusses seismological aspects of various proposed means of obscuring or hiding the seismic signatures of explosions from a surveillance network. These so-called evasion schemes are discussed from the points of view of both the evader and the monitor. The analysis will be conducted in terms of the USSR solely because that country is so vast and the geological/geophysical complexities of the country are so great that the complete spectrum of hypothesized evasion schemes requires discussion.

Part I of this paper was a general discussion of evasion schemes, placing the concepts within the reality of general factors influencing effective use of the techniques. Part II described techniques for quantitative investigation of evasion schemes when the only noise problem is normal microseismic noise, and gave analyses of several seismological networks as regards their capabilities to restrain imagined clandestine testing by the USSR under such noise conditions. This part of the paper (part III) describes techniques appropriate for use when the noise problem is interference due to codas of P and surface waves from earthquakes, and it will give analyses of capabilities of several seismological networks to restrain use of such codas for effective evasion.
An electronic long-period seismograph for surface-wave dispersion studies
Authors: Wielandt E. , Mitronovas W.
Published: September 2021

abstract

A long-period seismograph has been developed where the galvanometer photographic recording has been replaced by an electronic amplifier-filter circuit and ink recording, at comparable cost. The system has been tested carefully and found to be superior to conventional systems in some respects, especially in the stability of the transfer function and in the ease of installation and calibration. Critical but still satisfactory features are the dynamic range of the amplifier and the accuracy of the ink pen recorder. Both items are discussed in some detail.
Focal mechanism of the August 1, 1975 Oroville earthquake
Authors: Langston Charles A. , Butler Rhett
Published: September 2021

abstract

Long-period teleseismic P and S waves from the WWSS and Canadian networks are modeled to determine the focal parameters for the main shock in the Oroville earthquake series. Using the techniques of P first motions, wave-form synthesis, and phase identification, the focal parameters are determined as follows: dip 65°; rake −70°; strike 180°; depth 5.5 ± 1.5km; moment 5.7 ± 2.0 × 1024 dyne-cm; and a symmetric triangular time function 3 sec in duration. This is a north-south striking, westward dipping, normal fault with a small component of left-lateral motion. The time separation between the small foreshock and mainshock appears to be 6.5 sec at teleseismic distances, rather than 8.1 sec as observed at short distances.