bluuebunny/crossref_metadata_2025 huggingface dataset:
Methods of trichlorosilane synthesis for polycrystalline silicon production
Authors: Jarkin V. N. , Kisarin O. A. , Kritskaya T. V.
Published: September 2021

Novel technical solutions and ideas for increasing the yield of solar and semiconductor grade polycrystalline silicon processes have been analyzed. The predominant polycrystalline silicon technology is currently still the Siemens process including the conversion of technical grade silicon (synthesized by carbon-thermal reduction of quartzites) to trichlorosilane followed by rectification and hydrogen reduction. The cost of product silicon can be cut down by reducing the trichlorosilane synthesis costs through process and equipment improvement. Advantages, drawbacks and production cost reduction methods have been considered with respect to four common trichlorosilane synthesis processes: hydrogen chloride exposure of technical grade silicon (direct chlorination, DC), homogeneous hydration of tetrachlorosilane (conversion), tetrachlorosilane and hydrogen exposure of silicon (hydro chlorination silicon, HC), and catalyzed tetrachlorosilane and dichlorosilane reaction (redistribution of anti-disproportioning reaction). These processes remain in use and are permanently improved. Catalytic processes play an important role on silicon surface, and understanding their mechanisms can help find novel applications and obtain new results. It has been noted that indispensable components of various equipment and process designs are recycling steps and combined processes including active distillation. They provide for the most complete utilization of raw trichlorosilane, increase the process yield and cut down silicon cost
Charge-coupling effect in a Hall field element based on thin-film SOI-MOS transistor
Authors: Leonov A. V. , Murashev V. N. , Ivanov D. N. , Kirilov V. D.
Published: September 2021

The influence of the coupling effect on the parameters of field Hall elements based on thin-film MOS transistors has been studied. Analysis of the development of today’s microelectronics shows the necessity of developing the element base for high performance sensors based on silicon technologies. One way to significantly improve the performance of sensing elements including magnetic field sensors is the use of thin-film transistors on the basis of silicon on insulator (SOI) structures. It has been shown that field Hall sensors (FHS) may become the basis of high-performance magnetic field sensors employing the coupling effect occurring in the double gate vertical topology of these sensing elements. Electrophysical studies of FHS have been conducted for different gate bias and power supply modes. The results show that the coupling effect between the gates occurs in FHS if the thickness of the working layer between the gates is 200 nm. This effect leads to an increase in the effective carrier mobility and hence an increase in the magnetic sensitivity of the material. Thus field Hall elements based on thin-film transistors fabricated using silicon technologies provide for a substantial increase in the magnetic sensitivity of the elements and allow their application in highly reliable magnetic field sensors.
INIURIA IN CYBERSPACE
Authors: Frans E Marx
Published: September 2021

The purpose of this note is to investigate some real-world disputes that may arise as a result of unlawful conduct in virtual worlds. The note will firstly expand the background of virtual worlds and then sketch some scenarios, which could potentially lead to liability in law. The main focus will be on actionability in criminal law and delict in South African law. Special attention will be given to the question whether personality rights of members of virtual worlds can be infringed by, for instance, the rape of their avatars. The question whether liability for economic loss caused unlawfully to members of virtual worlds by other members of such worlds will also be addressed.
Low energy mechanical treatment of non-stoichiometric titanium carbide powder
Authors:   Institute of Strength Physics and Materials Science of the Siberian Branch of the Russian Academy of Sciences, Tomsk, Sablina Tatyana , Sevostyanova Irina ,   Institute of Strength Physics and Materials Science of the Siberian Branch of the Russian Academy of Sciences, Tomsk,   National Research Tomsk State University, Russian Federation
Published: September 2021

Introduction. The practical significance of non-stoichiometric titanium carbides TiCх in various fields of technology and in medicine is expanding. In this regard, it is important to investigate both methods of obtaining titanium carbide powder and its properties in a wide range of stoichiometry. One of the effective ways to influence the physical and mechanical properties of powder systems is its mechanical treatment. Under shock-shear action, which is realized during processing in a ball mill, mechanical energy is transferred to the powder system, as a result of which it is ground, centers with increased activity on newly formed surfaces are formed; phase transformations, crystal lattice deformation, amorphization, formation of defects, etc. are possible. The aim of this work is to study the effect of low-energy mechanical treatment in a ball mill on the structure, phase composition and parameters of the fine crystal structure of non-stoichiometric titanium carbide powder obtained by reduction of titanium oxide with carbon and calcium. Materials and methods. Powder of titanium carbide TiC, obtained by calcium carbonization of titanium oxide was investigated. The powder was treated in a drum type ball mill. The structure of the powders before and after treatment was studied using the Philips SEM 515 scanning electron microscope. The specific surface area was determined by the BET method. The phase composition and parameters of the fine crystal structure of powder materials were investigated by X-ray analyzes. Results and discussion. It was established that an increase of the time of mechanical treatment in a ball mill of a non-stoichiometric titanium carbide powder TiC0.7 leads to an increase in the specific surface area of the powder from 0.6 to 3.4 m2 / g, and the average particle size calculated from it decreases from 2 μm to 360 nm. It is shown that in the process of treatment of the non-stoichiometric titanium carbide TiC0.7 powder, its structural phase state changes. Powder particles consist of two structural components with different atomic ratio of carbon to titanium: TiC0.65 and TiC0.48. Mechanical treatment of titanium carbide powder leads to a decrease in the microstresses of the TiCx crystal lattice and the size of coherently diffracting domains (CDD) from 55 to 30 nm for the TiC0.48 phase. For the TiC0.65 phase, with an increase in the duration of mechanical treatment, as well as for TiC0.48, the size of CDD decreases, and the level of microdistortions of the crystal lattice increases. This indicates that in the process of mechanical treatment, not only the grinding of powder particles occurs, but also an increase in its defects.
Kinetic equations of creep and damage for description of materials with non-monotonic dependence of fracture strain on stress
Authors:   Lavrentyev Institute of Hydrodynamics of the Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Banshchikova Inna
Published: September 2021

Introduction. Reducing the level of damage accumulation during pressure treatment of materials at elevated temperatures in creep and close to superplasticity modes in the manufacture of parts can significantly increase its service life in the cold state. Finding temperature and power conditions leading to a reduction in damage of material during the production process and operation is an important task. The purposes of the work: 1) to show the possibility of using the Sosnin-Gorev creep and damage model for alloys with a non-monotonic dependence of strain at fracture on diagrams with creep curves; 2) to carry out comparative analysis of damage accumulation under conditions of uniaxial tension at constant stress and at constant strain rates for alloy with such a dependence. Research methods. Used scalar damage parameter is equated to the normalized deformation, i.e. to the ratio of the current strain to the fracture strain. To find the coefficients of relations creep and damage, the similarity of the creep curves in the normalized values “normalized strain – normalized time”, i.e. the presence of single normalized curve of damage accumulation is checked. The least squares method is used to approximate the experimental data. Numerical integration methods are used for comparative analysis of deformation modes. Results and discussion. Determination of the parameters of the creep and damage equations by the method of a single normalized curve is carried out on the example of experimental data for steel 12Kh18N10T (12Cr18Ni10Ti) at 850 °C, which has a minimum of fracture strain in diagrams with creep curves. Analysis of the static and kinematic modes of deformation for studied material showed that damage accumulation in both cases is practically the same for stresses close to the stress at which this minimum is reached. If the stresses are lower, then the lower level of damage accumulation will be in the kinematic mode; if the stresses above the minimum value, then the static mode will lead to a lower level of damage accumulation. Application. The obtained results can be useful when choosing rational modes of forming structural elements from alloys with a non-monotonic dependence of the fracture strain on stress, as well as in evaluating it for long-term strength during operation.
Synergetic approach to improve the efficiency of machining process control on metal-cutting machines
Authors:   Don State Technical University, Rostov-on-Don, Russian Federation, Zakovorotny Vilor , Gvindjiliya Valery ,   Don State Technical University, Rostov-on-Don, Russian Federation
Published: September 2021

Introduction. The efficiency of processing on metal-cutting machines is evaluated by the reduced cost of producing a batch of parts while ensuring the required quality. In modern production, parts are usually made on CNC machines. Today the CNC program and the trajectories of the machine tool actuators match each other with high accuracy, which, however, does not yet guarantee quality and efficiency of production. The definition of the CNC program is based on the knowledge base of rational modes, tools, coolant and etc. during processing. This base reflects some averaging over the set of machines, tools and processing conditions, and does not take into account changes in the properties of the dynamic system in the process of cutting. Subject. The paper deals with the synergistic matching of external control (CNC programs) and cutting dynamics (internal control). The internal control factors can be set a priori, as well as determined as a result of the influence of irreversible energy transformations in the cutting zone. The purpose of the work is to determine the law of controlling the trajectories of the machine's executive elements in such a way that, with changing properties of the dynamic cutting system, the required surface quality of the part and minimizing the intensity of tool wear are ensured during the processing of the part. Method and methodology. Mathematical simulation of the controlled dynamic system, which properties change due to the a priori set laws of variation of subsystem parameters, as well as changes in the cutting properties conditioned by the power of irreversible energy transformation is presented. Consideration of the power of irreversible energy transformations is necessary for predicting back-edge wear, changes in dynamic coupling parameters, and evolutionary restructuring of cutting dynamics. Results and Discussion. The regularity of matching the CNC program with the changing properties of the cutting process, which allows increasing the processing efficiency while ensuring the required quality of parts, is disclosed. A number of properties of the dynamic cutting system caused by changing trajectory of the longitudinal feed rate of the tool during processing of the shaft, the stiffness change of which is given, are revealed and analyzed.
SOCIAL SOLIDARITY AND COHESION OF DIASPORA AS FACTORS OF SOCIAL STABILITY IN THE CONVENTION OF THE COVID-19 PANDEMIC
Authors: Afanasieva Lyudmila , Glinskaya Lyudmila , Bukreeva Irina , Hlebova Natаlia
Published: September 2021

The article analyzes the phenomenon of social solidarity of the diaspora as one of the main directions of development of modern society in the context of challenges related to the problem of COVID-19. The analysis of social principles and genesis of comprehension of the category of social solidarity and cohesion on the materials of social philosophy is carried out. The essence of the main scientific approaches to the study of the concepts of social solidarity and cohesion is determined. Solidarity in work is seen as one of the prerequisites for stability and social order. The modern scientific definition of "social solidarity" in the social sciences means the unity of a group, class, or action that generates unity of interests, goals, standards, and mutual understanding. Solidarity processes by modern foreign and domestic researchers today are associated primarily with such phenomena as cooperation, cohesion, unity, public trust, the presence of common ideas, views and goals. Although social cohesion seems a difficult concept to study, researchers note its extreme importance in detailing the category of solidarity as a wide range of components: mutual assistance, trust, perception of difference, perception of justice, social inclusion, and so on. Since the spread of the COVID-19 virus and disease, people around the world have faced a large-scale emergency and an incomprehensible situation that is new to most modern societies. Therefore, the socio-cultural understanding of the pandemic as a global problem today acquires special significance for the search for the foundations of social cohesion, as a means of reducing tensions and social solidarity of communities. The authors argue that it is social solidarity and cohesion of the diaspora of communities and communities that is an effective means of social counteraction to modern destructive factors and challenges.
Minimally Invasive Techniques Used for Caries Management in Dentistry. A Review
Authors: Torres Paul J , Phan Hanthao T. , Bojorquez Ana K. , Garcia-Godoy Franklin , Pinzon Lilliam M
Published: September 2021

Objective: Minimally invasive techniques that use silver compounds and glass ionomer cement are suggested for caries management due to their effectiveness, simplicity, and low cost. The aim of this review is to examine the evidence supporting the use of silver compounds and glass ionomer cement in dentistry. Study design: Literature was searched using PubMed, Elsevier, EBSCO, Google scholar, AAPD and UABC’s database from 1958 to 2018 with the keywords: “Silver nitrate”, “silver diamine fluoride”, and “glass ionomer cement”. The selected studies were then fully read to prove their relevance for this review. Results: The use of glass ionomer cement and silver compounds were shown to be effective in arresting caries. These compounds reduce cariogenic microorganisms. Their chemical properties inhibit bacterial growth while promoting remineralization. They are simpler and less time consuming than conventional restorations. They also cause less discomfort and anxiety to patients. Silver compounds were shown to stain teeth and may burn the cornea if used in high concentration. These disadvantages limit the use of silver compounds to posterior teeth and require caution when handling. Conclusions: Minimally invasive therapies are easy to apply, non-invasive and affordable. Further studies should be done to provide more evidence of these techniques for caries management.
Transfer Deep Learning for Dental and Maxillofacial Imaging Modality Classification: A Preliminary Study
Authors: Kats Lazar , Vered Marilena , Kharouba Johnny , Blumer Sigalit
Published: September 2021

Objective: To apply the technique of transfer deep learning on a small data set for automatic classification of X-ray modalities in dentistry. Study design: For solving the problem of classification, the convolution neural networks based on VGG16, NASNetLarge and Xception architectures were used, which received pre-training on ImageNet subset. In this research, we used an in-house dataset created within the School of Dental Medicine, Tel Aviv University. The training dataset contained anonymized 496 digital Panoramic and Cephalometric X-ray images for orthodontic examinations from CS 8100 Digital Panoramic System (Carestream Dental LLC, Atlanta, USA). The models were trained using NVIDIA GeForce GTX 1080 Ti GPU. The study was approved by the ethical committee of Tel Aviv University. Results: The test dataset contained 124 X-ray images from 2 different devices: CS 8100 Digital Panoramic System and Planmeca ProMax 2D (Planmeca, Helsinki, Finland). X-ray images in the test database were not pre-processed. The accuracy of all neural network architectures was 100%. Following a result of almost absolute accuracy, the other statistical metrics were not relevant. Conclusions: In this study, good results have been obtained for the automatic classification of different modalities of X-ray images used in dentistry. The most promising direction for the development of this kind of application is the transfer deep learning. Further studies on automatic classification of modalities, as well as sub-modalities, can maximally reduce occasional difficulties arising in this field in the daily practice of the dentist and, eventually, improve the quality of diagnosis and treatment.
Modeling of strong ground motions from the 16 September 1978 Tabas, Iran, earthquake
Authors: Saikia Chandan K.
Published: September 2021

We have examined the adequacy of the published KS3 and L1 slip distribution models developed for the MS = 7.4 16 September 1978 Tabas earthquake (Hartzell and Mendoza, 1991) by modeling the high-frequency accelerograms recorded at Dayhook, Boshrooyeh, and Tabas stations. The agreement in peak ground acceleration (PGA) and duration between data and simulated accelerograms was chosen as the criterion for the model adequacy. The fault was specified with a seismogenic rupture area 95 km long and 45 km wide. We used a semi-empirical simulation method in which accelerograms from an aftershock from the 1979 Imperial Valley earthquake were used to represent the radiation pattern of P, SV, or SH waves for a source-receiver geometry. The fault surface is divided into many subfaults. The contributions from these subfaults, weighted by the slip amounts, were lagged and summed to simulate the accelerograms of the main event. We computed accelerograms assuming constant rake and variable rake on the fault plane. The former was simulated using the SUM slip model (i.e., the slip model representing the vector sum of the slip components at every point on the fault), and the latter was simulated by summing the accelerograms generated by the slip models of the dip-slip and strike-slip faults. The influence of the rise time of the main event was investigated. The KS3 asperity model produces results marginally better than the L1 asperity model. The duration is predicted, consistent with the data. The peak amplitudes of the simulated ground motions remain within a factor of 1.5 and 3 of the recorded data at Dayhook and Boshrooyeh, respectively, for the variable-rake and within a factor for 2.5 at both stations for the fixed-rake angle (KS3 model). The large PGA recorded on the Tabas accelerograms could not be reproduced, which warrants additional study. A notable agreement was obtained in the response spectra at Dayhook. This study demonstrates that accelerograms generated by an earthquake in one tectonic region can be transported to another tectonic region so that they can be used to represent the empirical radiation pattern of the subfaults in simulating ground motions for a large event.
Sources of primary and secondary microseisms
Authors: Cessaro Robert K.
Published: September 2021

Low-frequency (0.01 to 0.2 Hz) seismic noise, arising from pelagic storms, is commonly observed as microseisms in seismic records from land and ocean bottom detectors. One principal research objective, in the study of microseisms, has been to locate their sources. This article reports on an analysis of primary and secondary microseisms (i.e., near and double the frequency of ocean swell) recorded simultaneously on three land-based long-period arrays (Alaskan Long Period Array, Montana Large Aperture Seismic Array, and Norwegian Seismic Array) during the early 1970s. Reliable microseism source locations are determined by wide-angle triangulation, using the azimuths of approach obtained from frequency-wave number analysis of the records of microseisms propagating across these arrays. Two near-shore sources of both primary and secondary microseisms appear to be persistent in the sense that they are associated with essentially constant near-shore locations. Secondary microseisms are observed to emanate from wide-ranging pelagic locations in addition to the same near-shore locations determined for the primary microseisms.
A new method for absolute calibration of high-sensitivity accelerometers and other graviinertial devices
Authors: Tarbeyev Yu. V. , Krivtsov Ye. P. , Sinelnikov A. Ye. , Yankovsky A. A.
Published: September 2021

To investigate the dynamic characteristics of high-sensitivity graviinertial devices (accelerometers, seismometers, and others) it seems advantageous to use for the input signal the gravitational acceleration produced by bodies with a known mass distribution. This eliminates the need for moving the transducer under investigation. Such motion is needed in the inertial acceleration reproduction as well as for inclining a measuring instrument in the Earth's gravity field. Error in measuring the parameters of the transducer motion is determined by the uncertainties of the length- and angle-measuring instruments being used. Particularly, it concerns the angle measurement errors when the gravity field effects have been taken into account.

The existing methods for reproducing gravitational acceleration are based on the use of nonuniform fields of simple shape bodies (sphere, cylinder, and the like). These methods require calculation of the corresponding acceleration, taking into account the spatial mass distribution of the instrument sensing element. The commonly employed approximation results in a procedural error of the order of 10% and over.

It is proposed to calibrate a measuring instrument using a uniform, flat gravity field of varying direction. The set-up designed to realize this method reproduces varying accelerations over the frequency range 0.01 to 0.3 Hz with amplitude less than 1.3 × 10−7 m/sec2. This enables calibration of seismometers of various types with a higher accuracy.
Spatial and temporal distribution of slip for the 1992 Landers, California, earthquake
Authors: Wald David J. , Heaton Thomas H.
Published: September 2021

We have determined a source rupture model for the 1992 Landers earthquake (MW 7.2) compatible with multiple data sets, spanning a frequency range from zero to 0.5 Hz. Geodetic survey displacements, near-field and regional strong motions, broadband teleseismic waveforms, and surface offset measurements have been used explicitly to constrain both the spatial and temporal slip variations along the model fault surface. Our fault parameterization involves a variable-slip, multiple-segment, finite-fault model which treats the diverse data sets in a self-consistent manner, allowing them to be inverted both independently and in unison. The high-quality data available for the Landers earthquake provide an unprecedented opportunity for direct comparison of rupture models determined from independent data sets that sample both a wide frequency range and a diverse spatial station orientation with respect to the earthquake slip and radiation pattern. In all models, consistent features include the following: (1) similar overall dislocation patterns and amplitudes with seismic moments of 7 to 8 × 1026 dyne-cm (seismic potency of 2.3 to 2.7 km3); (2) very heterogeneous, unilateral strike slip distributed over a fault length of 65 km and over a width of at least 15 km, though slip is limited to shallower regions in some areas; (3) a total rupture duration of 24 sec and an average rupture velocity of 2.7 km/sec; and (4) substantial variations of slip with depth relative to measured surface offsets. The extended rupture length and duration of the Landers earthquake also allowed imaging of the propagating rupture front with better resolution than for those of prior shorter-duration, strike-slip events. Our imaging allows visualization of the rupture evolution, including local differences in slip durations and variations in rupture velocity. Rupture velocity decreases markedly at shallow depths, as well as near regions of slip transfer from one fault segment to the next, as rupture propagates northwestward along the multiply segmented fault length. The rupture front slows as it reaches the northern limit of the Johnson Valley/Landers faults where slip is transferred to the southern Homestead Valley fault; an abrupt acceleration is apparent following the transfer. This process is repeated, and is more pronounced, as slip is again passed from the northern Homestead Valley fault to the Emerson fault. Although the largest surface offsets were observed at the northern end of the rupture, our modeling indicates that substantial rupture was also relatively shallow (less than 10 km) in this region.
Investigation of the rupture process of the 28 June 1992 Landers earthquake utilizing TERRAscope
Authors: Dreger Douglas S.
Published: September 2021

Displacement seismograms recorded by TERRAscope for the 28 June 1992 Landers earthquake (MW 7.3) are deterministically modeled using a forward, point-source summation technique. Although the data set is sparse, it was possible to robustly determine important rupture parameters such as gross slip distribution, rupture velocity, rise time, and total source duration. The relatively simple approach lends itself to rapid application following large earthquakes, provided that a catalog of Green's functions appropriate for the region is available.

The fault used in the modeling of the Landers mainshock has a length of 70 km along strike and a width of 15 km along dip. A model was found in which the distribution and amplitude of slip at the surface matches the observed surface slip and provides a very good level of fit to the seismic data. Seismically, the Landers earthquake is characterized as two subevents. The peak slip of the first subevent is 10 km north of the epicenter and the second is 40 km northwest along strike from the epicenter. The seismic moment is distributed as 2 × 1026 dyne-cm to the first and 6 × 1026 to the second subevent, respectively. It was assumed in our modeling that the distribution of seismic moment along strike was the same at all depths. This assumption implies that slip at depth is 69% of that at the surface as a result of differences in the material properties in the velocity model. the sensitivities of the source model to rupture velocity and dislocation rise time were examined. A rupture velocity of 2.9 km/sec (80% of the shear-wave velocity) and a rise time of 1 to 3 sec were found to satisfy the data. The rise time is only a fraction of the total source process time of 24 sec, and implies that slip on the fault occurred within a narrow band (3 to 10 km), at any instant during the rupture.
Magnetic field observations in the near-field the 28 June 1992 Mw 7.3 Landers, California, earthquake
Authors: Johnston M. J. S. , Mueller R. J. , Sasai Y.
Published: September 2021

Recent reports suggest that large magnetic field changes occur prior to, and during, large earthquakes. Two continuously operating proton magnetometers, LSBM and OCHM, at distances of 17.3 and 24.2 km, respectively, from the epicenter of the 28 June 1992 Mw 7.3 Landers earthquake, recorded data through the earthquake and its aftershocks. These two stations are part of a differentially connected array of proton magnetometers that has been operated along the San Andreas fault since 1976. The instruments have a sensitivity of 0.25 nT or better and transmit data every 10 min through the GOES satellite to the USGS headquarters in Menlo Park, California. Seismomagnetic offsets of −1.2 ± 0.6 and −0.7 ± 0.7 nT were observed at these sites. In comparison, offsets of −0.3 ± 0.2 and −1.3 ± 0.2 nT were observed during the 8 July 1986 ML 5.9 North Palm Springs earthquake, which occurred directly beneath the OCHM magnetometer site. The observations are generally consistent with seismomagnetic models of the earthquake, in which fault geometry and slip have the same from as that determined by either inversion of the seismic data or inversion of geodetically determined ground displacements produced by the earthquake. In these models, right-lateral rupture occurs on connected fault segments in a homogeneous medium with average magnetization of 2 A/m. The fault-slip distribution has roughly the same form as the observed surface rupture, and the total moment release is 1.1 × 1020 Nm. There is no indication of diffusion-like character to the magnetic field offsets that might indicate these effects result from fluid flow phenomena. It thus seems unlikely that these earthquake-generated offsets and those produced by the North Palm Springs earthquake were generated by electrokinetic effects. Also, there are no indications of enhanced low-frequency magnetic noise before the earthquake at frequencies below 0.001 Hz.
Regional observation of a nuclear test from a vertical hydrophone array
Authors: Harris D. B. , D'Spain G. , Goldner A.
Published: September 2021

In order to evaluate the potential of water-column vertical hydrophone arrays for the measurement of continental events at regional distances, ocean acoustic data bases were examined for arrivals from these types of events. In 1987, the nuclear test LOCKNEY (mb 5.7, 37.28°N 116.38°W) was observed in the deep-ocean water column at a range of 900 km by the Vertical Line Array (VLA) at 35° N 126° W. Although the hydrophone data were contaminated below 10 Hz by array suspension noise and ocean acoustic noise, adaptive array processing allows us to extract the P and T phases. The root-mean-square (rms) direct P-wave amplitude in the water column is 100.6 dB referenced to 1 μPa in the 4- to 8-Hz band in a 20-sec window, which suggests a detection threshold of mb 5.2 in a deep oceanic environment at this range for a single hydrophone. The arrival time of the T phase [i.e., the portion of seismic energy that has somehow coupled into, and propagated within, the deep ocean sound channel (Aki and Richards, 1980)] is consistent with a P-wave conversion at the continental margin, assuming a velocity of 6 km/sec from NTS to the continental margin and acoustic propagation at 1.5 km/sec in the water column from the continent to the array.
A kinematic self-similar rupture process for earthquakes
Authors: Herrero A. , Bernard P.
Published: September 2021

The basic assumption that the self-similarity and the spectral law of the seismic body-wave radiation (e.g., ω-square model) must find their origin in some simple self-similar process during the seismic rupture led us to construct a kinematic, self-similar model of earthquakes. It is first assumed that the amplitude of the slip distribution high-pass filtered at high wavenumber does not depend on the size of the ruptured fault. This leads to the following “k-square” model for the slip spectrum, for k > 1/L: Δ~uL(k)=CΔσμLk2,

where L is the ruptured fault dimension, k the radial wavenumber, Δσ the mean stress drop, μ the rigidity, and C an adimensional constant of the order of 1. The associated stress-drop spectrum, for k > 1/L, is approximated by Δ~σL(k)=ΔσLk.

The rupture front is assumed to propagate on the fault plane with a constant velocity v, and the rise time function is assumed to be scale dependent. The partial slip associated to a given wavelength 1/k is assumed to be completed in a time 1/kv, based on simple dynamical considerations. We therefore considered a simple dislocation model (instantaneous slip at the final value), which indeed correctly reproduces this self-similar characteristic of the slip duration at any scale. For a simple rectangular fault with isochrones propagating in the x direction, the resulting far-field displacement spectrum is related to the slip spectrum as u˜(ω)=FΔ~u(kx=1Cdωv,ky=0),

where the factor F includes radiation pattern and distance effect, and Cd is the classical directivity coefficient 1/[1 − v/c cos (θ)]. The k-square model for the slip thus leads to the ω-square model, with the assumptions above. Independently of the adequacy of these assumptions, which should be tested with dynamic numerical models, such a kinematic model has several important applications. It may indeed be used for generating realistic synthetics at any frequency, including body waves, surface waves, and near-field terms, even for sites close to the fault, which is often of particular importance; it also provides some clues for estimating the weighting factors for the empirical Green's function methods. Finally, the slip spectrum may easily be modified in order to model other power-law decay of the radiation spectra, as well as composite earthquakes.
Observations of ambient noise and signal coherency on the Island of Hawaii for teleseismic studies
Authors: Li Yingping , Prothero William , Thurber Clifford , Butler Rhett
Published: September 2021

Ambient seismic noise conditions at several sites on the Island of Hawaii have been studied by analyzing noise power spectral density (PSD) and signal-to-noise ratio (SNR) of teleseisms. Broadband digital waveform data used in this study were collected during Project ALOHA. Direct comparison of noise PSD and SNR of teleseisms simultaneously recorded at stations on Hawaii and at station KIP on Oahu indicates that the stations on Hawaii are quieter than station KIP on Oahu in the frequency band of 0.1 to 1 Hz, suggesting that the Island of Hawaii can provide better noise conditions than station KIP. Our interpretation of this observation is that the area and volume of Hawaii are much larger than those of Oahu and distances to the coast for the stations on Hawaii are larger than that for station KIP on Oahu. Stronger attenuation and relatively low coherency for teleseismic signals on Hawaii in frequencies of 0.4 to 1.2 Hz are attributed to the presence of partial melt in the upper mantle. Teleseismic signal coherency is very low at frequencies above 2 Hz for a small array with a radius about 2 km. The relatively high coherency of the tangential component is strongly indicative of severe scattering effects caused by the heterogeneity in structure of the active volcanic area.
A multidisciplinary approach to seismic hazard in southern California
Authors: Ward Steven N.
Published: September 2021

A serious obstacle facing seismic hazard assessment in southern California has been the characterization of earthquake potential in areas far from known major faults where historical seismicity and paleoseismic data are sparse. This article attempts to fill the voids in earthquake statistics by generating “master model” maps of seismic hazard that blend information from geology, paleoseismology, space geodesy, observational seismology, and synthetic seismicity. The current model suggests that about 40% of the seismic moment release in southern California could occur in widely scattered areas away from the principal faults. As a result, over a 30-yr period, nearly all of the region from the Pacific Ocean to 50 km east of the San Andreas Fault has a greater than 50/50 chance of experiencing moderate shaking of 0.1 g or greater, and about a 1 in 20 chance of suffering levels exceeding 0.3 g. For most of the residents of southern California, thelion's share of hazard from moderate earthquake shaking over a 30-yr period derives from smaller, closer, more frequent earthquakes in the magnitude range (5 ≦ M ≦ 7) rather than from large San Andreas ruptures, whatever their likelihood.
The 1737 Calcutta earthquake and cyclone evaluated
Authors: Bilham Roger
Published: September 2021

Catalogs of historically devastating earthquakes (e.g., Dunbar et al., 1992) contain an entry for an earthquake in Calcutta in 1737 that is held responsible for the loss of 300,000 lives, thus rendering it one of the three most disastrous earthquakes in history. Yet, evidence for a severe earthquake is weak, consisting of anonymous reports conveyed to Europe 6 months later by merchant ships returning from Bengal. Official accounts of the disaster submitted to the East India Company headquarters in London list 3000 fatalities and omit mention of an earthquake. If the 11 October 1737 Calcutta earthquake is to remain on lists of catastrophic earthquakes, the following issues need to be resolved: the discrepancy between the 1737 urban population of Calcutta (<20,000) and the number of claimed fatalities, the difficulty in distinguishing between damage from shaking and hurricane force winds and flooding that occurred during the same night, and the contradiction between the number of nocturnal deaths and the apparent earthquake resistance of hatched roof dwellings typical of eighteenth century rural Bengal. It is possible that earthquake damage may have been minimal or nonexistent.
Modeling viscoelastic waves: a comparison of ray theory and the finite-difference method
Authors: Quiroga-Goode Gerardo E. , Krebes E. S. , Le Lawrence H. T.
Published: September 2021

Two techniques for computing ray synthetic seismograms in anelastic media produce substantially different results in a model consisting of an elastic half-space overlying a stack of anelastic layers (Krebes and Slawinski, 1991). The first technique, the stationary ray method, involves an evaluation of the wave field integral by the method of steepest descent, and yields complex rays. In the second, the conventional ray method, it is assumed that the attenuation vector of the initial ray segment (in the elastic part of the model) is zero (which is not the case for the stationary ray). The essential difference between these two methods is that the stationary ray method gives minimum travel-time rays, thus agreeing with Fermat's principle. Krebes and Slawinski (1991) relied upon this fact to suggest that the stationary ray method is the correct method. However, since the method raises some conceptual peculiarities (e.g., the initial ray segment of the stationary ray is an inhomogeneous elastic wave propagating as a body wave), it is important to verify their results and conclusions with an independent solution of the problem; we use a numerical finite-difference solution. By making direct comparisons between synthetic seismograms obtained with the stationary ray method, conventional ray method, and finite differences, we find that the stationary ray method agrees with the finite-difference solution better than the conventional ray method.
Integral equation method for plane crack with arbitrary shape in 3D elastic medium
Authors: Fukuyama Eiichi , Madariaga Raul
Published: September 2021

We have derived stress integral equations for an arbitrary shaped plane crack in a three-dimensional (3D) infinite homogeneous isotropic elastic medium. First we obtained the integral equation for static crack, which is consistent with previous works. Then we derived a new boundary integral equation for the study of dynamic tensile and shear cracks. We removed the hypersingularity that appears in the usual formulation of the stress-boundary integral equation method by a regularization technique. The dynamic stress integral equation consists of three terms which can be physically explained. The first term is a modification of the static solution, the second one represents the diffraction of waves at slip discontinuities, and the last term is related to the effect of an instantaneous change in slip velocity. The first term controls the overall shape of the stress drop inside the crack. This term is important when we consider the final stress drop on the fault. However, the second and the third terms are dominant at a moving crack tip, and are responsible for the radiation of P and S waves. They are also very important for the application of a fracture criterion at the rupture front. Using this boundary integral equation we have calculated several numerical examples for both the static and dynamic fault models.
Analysis of broadband records from the 28 June 1992 Big Bear earthquake: Evidence of a multiple-event source
Authors: Jones Laura E. , Hough Susan E.
Published: September 2021

The 28 June 1992 Big Bear earthquake occurred at 15:05:21 GMT and is considered to be an aftershock of the earlier Mw = 7.3 Landers earthquake. From overall aftershock locations and long-period focal studies, rupture is generally assumed to have propagated northeast. No surface rupture was found, however, and the mainshock locations determined from both strong motion and TERRAscope data are mutually consistent and do not lie on the assumed fault plane. Further, directivity analysis of records from the TERRAscope array suggests significant short- and long-period energy propagating northwest along the presumed antithetic fault plane. This observation is supported by significant early aftershocks distributed along both the presumed rupture plane and the antithetic plane to the northwest. An empirical Green's function (eGf) approach using both the Mw = 5.2, 28 June 1992 14:43 GMT foreshock and the Mw = 5.0 17 August 1992 aftershock produces consistent results and suggests that the Big Bear event comprised at least two substantial subevents. From the eGf results, we infer that the second and possibly a third subevent occurred on the presumed (northeast striking) mainshock rupture surface, but that significant moment release occurred on the antithetic northwest striking surface. We present results from line-source fault modeling of broadband displacement recordings of the Big Bear mainshock, which indicate that a two-fault event is necessary to produce the observed waveforms. The limitations imposed by the mainshock location and directivity analysis require that the initial rupture be towards the northwest, striking 320°. This was followed approximately 4 sec later by bilateral rupture along a northeast-southwest fault that strikes 50° east of north.
Magnitude-dependent variance of peak ground acceleration
Authors: Youngs R. R. , Abrahamson N. , Makdisi F. I. , Sadigh K.
Published: September 2021

We examine the variability of peak horizontal and vertical accelerations of the large California strong-motion data set for the time period 1957 to 1991 and find a statistically significant dependence of the standard error on earthquake magnitude. Specifically, the standard error decreases with increasing magnitude. The analysis was conducted using a rigorous methodology that examines both earthquake to earthquake (inter-event) variability and within earthquake (intra-event) variability. The magnitude dependence is stronger for inter-event variability than intra-event variability, and stronger for horizontal peak acceleration than for vertical peak acceleration. The data from the recent Landers, Big Bear, and Northridge earthquakes are consistent with these results.
Source characterization and fault plane determination for MbLg = 1.2 to 4.4 earthquakes in the Charlevoix Seismic Zone, Quebec, Canada
Authors: Li Yingping , Doll Charles , Toksöz M. N.
Published: September 2021

Two earthquake doublets and two multiplets recorded by the Charlevoix Telemetered Network (CLTN) in the Charlevoix Seismic Zone (CSZ) of southern Quebec, Canada, have been analyzed using an empirical Green's function (EGF) method to derive the relative source time functions (RSTF's) of seven master events with MbLg = 1.2 to 4.4. We identified the doublets and multiplets using a waveform cross-correlation and relative event location technique to verify that each earthquake pair had similar focal mechanisms and hypocentral locations. Three-component S waveforms recorded by the high dynamic range (126 dB) instrumentation of the CLTN were used to extract the RSTF's.

The RSTF's reveal that six of the seven events are simple with single-source pulses having durations of 0.05 to 0.2 sec. Another earthquake (920310-0545, M 3.3) appears to be a double event with two episodes of rupturing. Azimuthal variations of the RSTF pulse amplitudes and widths provide strong evidence for the rupture directivities of five of the earthquakes (M = 1.2 to 4.4). The azimuthal variations in the RSTF pulse amplitudes were used to estimate the rupture directions and rupture velocities. Lower-bound estimates of the rupture velocity range from 0.5 to 0.7 Vs. Estimates of the rupture direction were combined with P-wave focal mechanisms for the four largest events (M 3.3 to 4.4) to identify the fault plane for these earthquakes. Source parameters were measured for the RSTF's of the master events, including seismic moments of 3.5 × 1018 to 5.3 × 1021 dyne-cm, fault radii of 100 to 330 m, and static stress drops of 2 to 90 bars. The fault radii and stress-drop estimates for M > 3 events agree well with estimates obtained by other researchers for M ∼ 3 to 4.5 earthquakes in the CSZ. We also observed apparent scaling between the stress drop and the earthquake size, which has been reported in other studies of stress drop in northeastern North America.
Configuring a seismographic network for optimal monitoring of fault lines and multiple sources
Authors: Steinberg David M. , Rabinowitz Nitzan , Shimshoni Yair , Mizrachi Daphna
Published: September 2021

The geometric configuration of a seismographic network has important consequences for the ability to determine hypocenters with high precision. We present a method for optimal configuration when the network must monitor a system of faults. Our optimality criterion is drawn from the statistical theory of experimental design and can be effeciently maximized using an extension of the DETMAX algorithm. Our work generalizes that of Rabinowitz and Steinberg (1990), which treated the problem of optimal network configuration for monitoring a point source.
Working Memory Capacity and the Implementation of New Information During Task Repetition
Authors: De Paula Socorro Gardenia Carvalho , Tavares Maria da Glória Guará , Weissheimer Janaina
Published: September 2021

According to Bygate and Samuda (2005), task repetition can help students to integrate what they know with what they do, since it allows two different experiences of the same requirements of a task. Thus, such differences can result in changes from one speech production to another. Therefore, the objective of this study is to investigate which individuals, whether those with higher or lower working memory capacity, implement more new information during task repetition. A sample of 28 students from a public university underwent data collection which consisted of a working memory test (Speaking Span Test), a translation task, repeated twice, and two questionnaires. In general, the results showed that higher working memory capacity individuals were those who most implemented new information during task repetition, in terms of the implementation of new lexical items. The results are discussed in the light of the literature in the fields of working memory and task repetition. Final considerations are made suggesting that task repetition, in addition to bringing gains to oral production in terms of fluency and accuracy, for example, makes participants in the higher working memory capacity group able to allocate more cognitive and attentional resources to implement a greater number of new lexical items in second task performances.