bluuebunny/crossref_metadata_2025 huggingface dataset:
SHORT MESSAGE SERVICES AND E-CONTRACTING Jafta v Ezemvelo KZN Wildlife [2008] 10 BLLR 954 (LC)
Authors: Sylvia Papadopoulos
Published: September 2021

With the emergence of internet-based e-commerce in the last decade of the 20th century, commercial activity entered into a new era and it has been said that modern society is now past the point where we can treat the Internet and indeed all things electronic as if they were part of some kind of fictional or fantasy realm that is only tangentially connected to the real world. This was brought into clear focus with a recent decision handed down by the Durban Labour Court, where they also warned that, even though e-mails and SMS’s and the language that these text messages carry seem informal, treating them as having no legal effect would be a mistake (Jafta v Ezemvelo KZN Wildlife [2008] 10 BLLR 954 969F).
BURN VICTIMS AND SKIN DONATIONS: A LEGAL PERSPECTIVE
Authors: Magda Slabbert  , Bonnie Venter
Published: September 2021

This article highlights the need for skin donations to treat burn wounds. South Africa has an exceptionally high number of burn wound victims per annum. The ideal way to treat burn wounds is to transplant skin from another part of the patient’s body to the affected areas (autografts). Unfortunately, this is not always possible or feasible and in those cases skin from cadavers (allografts) should be used, but this can only be done if the deceased has indicated a wish during his or her lifetime that tissue be donated for transplantation use after death. If the deceased has not indicated his or her wish to be a tissue donor, family members could be asked to consent to a donation. The article looks at the legal requirements in South Africa for a valid skin donation as well as the requirements should skin be imported owing to a lack of enough tissue donors in the country. This position is contrasted to the position in the United Kingdom with a view to establishing whether South Africa can learn from another jurisdiction concerning the procurement of skin for transplantation. The possible reasons that people do not donate skin are also touched upon.
On the problem of tool destruction when obtaining fixed joints of thick-walled aluminum alloy blanks by friction welding with mixing
Authors:   Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences, Tomsk, Kalashnikov Kirill , Chumaevskii Andrey ,   Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences, Tomsk, Kalashnikova Tatiana ,   Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences, Tomsk, Ivanov Aleksey ,   Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences, Tomsk, Rubtsov Valery ,   Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences, Tomsk, Kolubaev Evgeny ,   Institute of Strength Physics and Materials Science of Siberian Branch of Russian Academy of Sciences, Tomsk, Bakshaev Vladimir ,   SESPEL Cheboksary enterprise, CJSC, Cheboksary, Chuvash Republic, Russian Federation
Published: September 2021

Introduction. Among the technologies for manufacturing rocket and aircraft bodies, marine vessels, and vehicles, currently, more and more attention is paid to the technology of friction stir welding (FSW). First of all, the use of this technology is necessary where it is required to produce fixed joints of high-strength aluminum alloys. In this case, special attention should be paid to welding thick-walled blanks, as fixed joints with a thickness of 30.0 mm or more are the target products in the rocket-space and aviation industries. At the same time, it is most prone to the formation of defects due to uneven heat distribution throughout the height of the blank. It can lead to a violation of the adhesive interaction between the weld metal and the tool and can even lead to a destruction of the welding tool. The purpose of this work is to reveal regularities of welding tool destruction depending on parameters of friction stir welding process of aluminum alloy AA5056 fixed joints with a thickness of 35.0 mm. Following research methods were used in the work: the obtaining of fixed joints was carried out by friction welding with mixing, the production of samples for research was carried out by electric erosion cutting, the study of samples was carried out using optical metallography methods. Results and discussion. As a result of performed studies, it is revealed that samples of aluminum alloy with a thickness of 35.0 mm have a heterogeneous structure through the height of weld. There are the tool shoulder effect zone and the pin effect zone, in which certain whirling of weld material caused by the presence of grooves on tool surface is distinctly distinguished. It is shown that the zone of shoulders effect is the most exposed to the formation of tunnel-type defects because of low loading force and high welding speeds. It is revealed that tool destruction occurs tangentially to the surface of the tool grooves due to the high tool load and high welding speeds.
Further Micro-scaled MEDI (Macronutrient Extraction and Determination from Invertebrates) v1
Authors: P Cuff Jordan
Published: September 2021

Macronutrients, comprising carbohydrates, proteins and lipids, underpin many ecological processes, but their quantification in ecological studies is often inaccurate and laborious, requiring large investments of time and bulk samples, which make individual‐level studies impossible. This is a protocol for the direct, rapid and relatively low‐cost determination of macronutrient content from single small macroinvertebrates. Macronutrients are extracted by a sequential process of soaking in 1:12 chloroform:methanol solution to remove lipid and then solubilising tissue in 0.1M NaOH. Proteins, carbohydrates and lipids were determined by colorimetric assays from the same individual specimens. Macronutrient Extraction and Determination from Invertebrates (MEDI) can directly and rapidly determine macronutrient content in tiny (dry mass <1mg). Using MEDI, the total macronutrient content of over 50 macroinvertebrates can be determined within around 3days of collection at a cost of ~$1.35 per sample.
THE CONCEPT OF «DIASPORA» IN RESEARCH WORKS OF FOREIGN SCIENTISTS: PARTICULARITIES OF INTERPRETATIONS AND USE
Authors: Averianova Nina
Published: September 2021

The author of the article shows that the term «Diaspora» is often found in foreign scientific circulation. Scientists are gradually introducing new understandings and meanings into the content of the concept of «Diaspora». The definition of «Diaspora» is based on various criteria and characteristics - ethnic, religious, economic, political, etc. And although this word was used in the distant past, however, fundamental developments regarding the concept of «Diaspora» appeared relatively long ago. In the 90s of the twentieth century, a large number of different definitions and typologies of diasporas were proposed, even a new discipline was formed – Diaspora studies. It was during this period that the use of terms such as «Diaspora» and «transnationalism» increased. The author emphasizes the importance of research by such foreign scientists as John A. Armstrong, Rogers Brubaker, Michel Bruneau, Nicholas Van Hear, Milton J. Esman, James Clifford, Robin Cohen, Alain Medam, William Safran, Valeriy Tishkov, Thomas Faist, Gabriel Sheffer. Analyzes the well-known works of these authors regarding the definition of the concept of «Diaspora» and its types. Draws attention to the fact that diasporas today are not only historically formed communities that live outside the country of origin and adhere to ethnocultural traditions. These are certain forces of influence on the authorities of the country of residence and a political instrument in the international arena.
The development of modern technologies, expanded access to cyberspace has also affected the functioning of the diasporas. These changes were reflected in new terms – «e-diasporas», «net-diasporas», «web-diasporas», «Onlinediasporas», «digital diasporas». Proves the need for a clear definition of the concept of «Diaspora», because the process of Diaspora takes on new forms and the influence of diasporas is increasing both in the countries of residence and in the countries of origin. The lack of a definition of the specified period directs scientists to further study the problem.
THE INTELLECTUAL SUPPORT OF RESTORING UKRAINE’S INDEPENDENCE: COLLABORATION BETWEEN UKRAINIANS IN UKRAINE AND ABROAD (DEDICATED TO THE 30th ANNIVERSARY OF UKRAINE’S INDEPENDENCE)
Authors: Voropayeva Tetiana
Published: September 2021

The author of the article analyzes the collaboration of the domestic and foreign Ukrainians alike in the perennial intellectual support of restoring Ukraine‟s independence. The most important figures in this process were: V. Antonovych, M. Hrushevsky, M. Kostomarov, A. Krymsky, M. Maksymovych, I. Ogienko, O. Potebnya; V. Vytvytsky, M. Globenko, V. Holubnychy, S. Hordynsky, E. Glovinsky, D. Dontsov, A. Zhukovsky, Z.E. Kohut, I. Koshelivets, B. Kravtsiv, I. Krypyakevych, V. Kubiyovych, Z. Kuzelya, Y. Kuchabsky, V. Markus, M. Mikhnovsky, O. Ogloblin, E. Onatsky, J. asternak, E.-Yu. Pelensky, V. Petrov, S. Plokhii, N. Polonska-Vasylenko, O. Pritsak, I. Rakovsky, S. Rudnytsky, S. Smal-Stotsky, M. Stakhiv, O. Subtelny, A. Figol, V. Khvoyka, M. Chubaty, V. Shcherbakivsky, S. Yaniv; V. Balushok, V. Baran, M. Braichevsky, I. Gel, P. Grigorenko, J. Dashkevych, I. Dziuba, I. Drach, M. Zhulynsky, L. Zaliznyak, J. Isayevych, J. Kalakura, I. Kandyba, P. Kononenko, L. Lukyanenko, O. Nelga, G. Pivtorak, M. Popovych, O. Romanov, M. Rudenko, E. Sverstyuk, S. Segeda, V. Sergiychuk, V. Smoliy, V. Stus, M. Tymoshyk, V. Chornovil and others.
The publishing of „Encyclopedia of Ukraine‟ was an extremely important event that became the means to centralize the worldview of the meaning field of the Ukrainian identity. „Encyclopedia of Ukraine‟ (Professor Volodymyr Kubiyovych, chief editor) is a scientific publication that combines the most significant systemized information in different scientific branches about the Ukrainianship, Ukraine, and Ukrainian world. Since Ukraine's study has a huge worldview potential, it is necessary to further fortify its influence on the forming of a complete worldview and common identity of Ukrainian citizens.
We know that any political, economic, historical, and ethnocultural information requires the meaning processing when it is being studied. Because meaning is a unit of inner world of identity (O. Leontiev), while „the strive for the meaning‟ is one of the most efficient motivators of person's tendencies, and once it‟s gone people get trapped in an existential vacuum, alienation, depression, despair, etc. (V. Frankl). The meaning throughout the entire „Encyclopedia of Ukraine‟ could become a determinant of the worldview formation of the meaning field in Ukrainian identity (both personal and general). So, „Encyclopedia of Ukraine‟ with meaningful information and different forms (signs, symbols, images, axiological, etc.) of meaning representation may become a source of Ukraine‟s study competency and a system forming factor of centralizing the worldview of the meaning field of the Ukrainian identity, which was provided by the process of intellectual support of Ukraine's independence.
PROBLEMS AND PROSPECTS OF THE BELARUSIAN DIASPORA IN PRESENT-DAY UKRAINE IN PERSPRCTIVE OF THE BELARUSIAN REVOLUTION OF DIGNITY AND FREEDOM
Authors: Grabovska Iryna , Тalko Тetiana , Tovmash Dmytro
Published: September 2021

The problem of emigration to Ukraine of a significant number of Belarusian citizens due to the events of the Belarusian anti-Lukashenko revolution of dignity and freedom, which began in this country in August 2020 after the presidential election, is discussed in the article. It is noted that at the beginning of 2021 the number of those who fled to Ukraine, hiding from repression and persecution by the Belarusian authorities, was already more than 75 thousand people. In the future, the number of Belarusian refugees is projected to increase to 100-120 thousand people by 2021. It is unknown yet which of these people will join the Belarusian Diaspora in Ukraine, which before these events was the second largest Diaspora in Ukraine. And who considers Ukraine only as a territory of transit further to the East, or the West, for example, to Poland.
In connection with these events, the Ukrainian state and society faced a series of challenges, problems and threats, to which it will be necessary to find adequate answers. In particular, the authors of the article consider unjustified some warnings expressed by patriotic Ukrainian citizens about the possible growth of pro-Russian sentiment in Ukraine due to the arrival and settlement of Belarusian refugees here. It seems logical that people with pro-Russian sentiments would rather immigrate to Russia than come to Ukraine.
It is expected that a significant problem for the newly arrived Belarusians may be the understanding and establishment of dialogue and contacts with the "old" Belarusian Diaspora in Ukraine because of its commitment to Lukashenko and sympathy for Russia. It is concluded that Belarusian citizens, active participants in the Belarusian revolution, can become a useful enzyme for accelerating the reform processes in Ukraine and will contribute to further democratic and pro-European movement in this area.
Oral Health, Dental Care and Nutritional Habits of Children with Cerebral Palsy during Conductive Education
Authors: Orsós M , Antal D , Veres DS , Nagy K , Németh O
Published: September 2021

Objective: Regarding the 2011 census in Hungary, the number of children with movement deficiences can be around 7,000. These children with special health care needs are considered to be a vulnerable group even from a dental point of view. In our dental program, we gain comprehensive information about patients’ oral health, health behavior, and monitor dental care. Study design: A total of 199 children went through a full pediatric dental examination, children with cerebral palsy were categorized into five different levels (GMFCS) and children without motor disfunction into two groups. We analyzed the df-t and DMF-T values. Oral hygiene routine, dental care, gingivitis, demographic characteristics, nutritional habits odds ratio to df-t and DMF-T were surveyed. Results: The mean df-t and DMF-T was 1.87 and 1.15 out of a total of 199, and the group that scored worse was the GMFCS II. The mean RI (restorative index) was 18.12% and 27% for decidous and permanent teeth, respectively. The prevalence of gingivitis was 66.7%. Conclusion: The results of our research point to the fact that children with cerebral palsy have difficulties in developing and maintaining proper oral health due to their disadvantages and therefore require special care and attention.
Influence of Irrigation Protocol on Peroxide Penetration into Dentinal Tubules Following Internal Bleaching: A Confocal Laser Scanning Microscopy Study
Authors: Elbahary Shlomo , Gitit Zafrir , Flaisher-Salem Nurit , Azem Hanaa , Shemsesh Hagay , Rosen Eyal , Tsesis Igor
Published: September 2021

Introduction: Discoloration of anterior teeth can result in cosmetic impairment in young children. The walking bleach technique stands out because of its esthetic results with minor side effects. Little information is available regarding the influence of various irrigation solutions on peroxide penetration. The aim of this study is to evaluate the influence of different irrigation protocols on peroxide penetration into dentinal tubules using confocal laser scanning microscopy (CLSM).

Study design: Cavity preparations were made in 50 extracted permanent premolars. The teeth went through different irrigation sequences: A. control B. saline C. EDTA, NaOCl D. phosphoric acid E. EDTA, NaOCl, phosphoric acid. Then, mixture of fluorescent dyed sodium perborate paste was placed along the pulp chamber and the coronal access cavity, and was refilled at days 7, 14 and 21.

Results: The minimal and maximal penetration depths were 324 and 3045 μm, respectively, with a mean of 1607μm. The stained areas were significantly larger in the buccal and lingual directions (P<0.05). Groups B and C showed significantly larger penetration in weeks 2 and 3 compared to week 1 (P<0.05). Group D and E showed significantly larger penetration compared to groups B and C at all times (P<0.05).

Conclusion: Bleaching agents penetrate to the extra-radicular region of teeth; however, the level of peroxide penetration is significantly higher when the irrigation sequence consists of phosphoric acid prior the bleaching agent placement.
Association of Salivary Zinc Levels to Dental Caries and Body Mass Index. A Comparative Study
Authors: Sharma Akhilesh , Subramaniam Priya
Published: September 2021

Background and objectives: Role of salivary zinc to dental caries and body weight has not been studied extensively in children. The aim of the present study was to evaluate the relationship between salivary zinc and caries in overweight/obese Indian children. Study design: One hundred and sixty children aged 8–12 years of both genders were divided into two groups of eighty each based on their body mass index into normal weight and overweight/obese. Each child was assessed for their caries experience in primary and permanent dentition. Unstimulated salivary samples were collected from each child to estimate zinc levels by atomic absorption spectrophotometer. Data was subjected to statistical analysis. Results: The mean caries score among the overweight/obese children was 2.2±3.9 and 0.7±1.5 in the primary and permanent dentition respectively compared to the 2.0±2.6 and 0.2±0.5 respectively among normal weight children. Mean salivary zinc levels in overweight/obese children were 0.36±0.27 ppm compared to normal weight children of 0.81±0.46 ppm. Conclusion: Overweight/obese children demonstrated significantly lower salivary zinc levels and higher caries experience in permanent dentition. Salivary zinc levels showed a positive but weak association to caries in permanent dentition in both groups. Salivary zinc levels showed a negative non-significant correlation to caries in primary dentition among the children with higher BMI.
Regional propagation characteristics and source parameters of earthquakes in northeastern North America
Authors: Boatwright John
Published: September 2021

The vertical components of the S wave trains recorded on the Eastern Canadian Telemetered Network (ECTN) from 1980 through 1990 have been spectrally analyzed for source, site, and propagation characteristics. The data set comprises some 1033 recordings of 97 earthquakes whose magnitudes range from M ≈ 3 to 6. The epicentral distances range from 15 to 1000 km, with most of the data set recorded at distances from 200 to 800 km. The recorded S wave trains contain the phases S, SmS, Sn, and Lg and are sampled using windows that increase with distance; the acceleration spectra were analyzed from 1.0 to 10 Hz. To separate the source, site, and propagation characteristics, an inversion for the earthquake corner frequencies, low-frequency levels, and average attenuation parameters is alternated with a regression of residuals onto the set of stations and a grid of 14 distances ranging from 25 to 1000 km. The iteration between these two parts of the inversion converges in about 60 steps. The average attenuation parameters obtained from the inversion were Q = 1997 ± 10 and γ = 0.998 ± 0.003. The most pronounced variation from this average attenuation is a marked deamplification of more than a factor of 2 at 63 km and 2 Hz, which shallows with increasing frequency and increasing distance out to 200 km. The site-response spectra obtained for the ECTN stations are generally flat. The source spectral shape assumed in this inversion provides an adequate spectral model for the smaller events (Mo < 3 × 1021 dyne-cm) in the data set, whose Brune stress drops range from 5 to 150 bars. For the five events in the data set with Mo ≧ 1023 dyne-cm, however, the source spectra obtained by regressing the residuals suggest that an ω2 spectrum is an inadequate model for the spectral shape. In particular, the corner frequencies for most of these large events appear to be split, so that the spectra exhibit an intermediate behavior (where |ü(ω)| is roughly proportional to ω).
Modeling of energy amplification recorded within Greater Los Angeles using irregular structure
Authors: Saikia Chandan K. , Dreger Douglas S. , Helmberger Donald V.
Published: September 2021

We have investigated energy amplification observed within Greater Los Angeles basin by analyzing regional waveforms recorded from several Nevada Test Site (NTS) nuclear explosions. Although the stations are located nearly at the same azimuth (distances ranging from 350 to 400 km), the seismograms recorded in Compton (the central part of the basin), Long Beach (the southern edge of the basin), and downtown Los Angeles are remarkably different, even for a common explosion. Following the onset of Lg waves, the Long Beach sites have recorded surface waves for more than 100 sec. From one explosion, the sites within downtown Los Angeles have recorded seismograms with strong 3-sec surface waves. These waves are not observed on the seismograms recorded in the neighboring hard-rock site California Institute of Technology (CIT) station. Thus, they must have been generated by local wave guides. Numerically, we modeled these 3-sec waves by convolving the CIT seismogram with the response of a sedimentary strata dipping gently (about 6°) from CIT toward downtown. We also examined the irregular basin effect by analyzing the variation of cumulative temporal energy across the basin relative to the energy recorded at CIT from the same explosion. Variation up to a factor of 30 was observed. To model the energy variation that is caused by extended surface waves in the Long Beach area, we used numerically simulated site transfer functions (STF) from a NNE-SSW oriented two-dimensional basin structure extending from Montebello to Palos Verdes that included low-velocity sedimentary material in the uppermost layers. These STFs were convolved with the CIT seismogram recorded from the MAST explosion. To simulate elongated duration of surface waves, we introduced in the upper sedimentary structure some discontinuous microbasin structures of varying size, each microbasin delaying the seismic waves propagating through them. Consequently, the surface-reflected phases through these structures are delayed and reflected into the upper medium by the underlying interfaces. This mechanism helps delayed energy to appear at a later time and result in a longer time duration at sites located at southern edge of the basin.
New finite-difference methods for free surfaces with a stability analysis
Authors: Stacey Richard
Published: September 2021

New finite-difference formulations are given for the free surface of an elastic solid. It is argued that the new methods are better than earlier formulations in terms of both accuracy and stability. This conclusion is based on some new algebraic results and on a thorough analysis of the stability problems that can occur. It is backed up by extensive numerical testing. The explicit grid mode that makes the earlier “composed approximation” unstable is constructed. The construction generalizes to give general tests for instabilities. A criterion for using formulations that have relatively minor stability problems (the “useful life”) is stated and applied.
A note on surface motion of inhomogeneous alluvial valleys due to incident planeSHwaves
Authors: Clements David L. , Larsson Ashley
Published: September 2021

The scattering and diffraction of harmonic SH waves by an arbitrarily shaped inhomogeneous alluvial valley in a layered material is considered. A new formalism is used to obtain the appropriate wave solutions for inhomogeneous media, and these are employed together with the boundary integral equations to obtain numerical solutions for some important particular problems.
Estimation of source characteristics using plane wave decomposition
Authors: Shtivelman V. , Loewenthal D.
Published: September 2021

We present a simple and effective method for deterministic estimation of time-space characteristics of seismic sources. These characteristics (time signature, spatial distribution, and radiation pattern) can be important for such geophysical applications as deconvolution, inversion, and Amplitude Versus Offset (AVO) analysis. The proposed method can be applied to two-dimensional marine data obtained using the dual streamer acquisition technique. Our estimation procedure is based on decomposition of the measured wave field into plane waves with subsequent separation of up- and downgoing components. After the separation, a simple estimation algorithm formulated for the one-dimensional case is applied to each plane wave. Then the amplitudes of the plane waves measured at various propagation angles can be used to estimate the angular distribution of source radiation. Finally, the source time function and spatial distribution are estimated by synthesis of the plane waves. A number of numerical examples show that the proposed estimation procedure can produce good estimates of the source characteristics.
State of stress from focal mechanisms before and after the 1992 landers earthquake sequence
Authors: Hauksson Egill
Published: September 2021

The state of stress in the Eastern California Shear Zone (ECSZ) changed significantly because of the occurrence of the 1992 Mw 6.1 Joshua Tree and the MW 7.3 Landers earthquakes. To quantify this change, focal mechanisms from the 1975 Galway Lake sequence, the 1979 Homestead Valley sequence, background seismicity from 1981 to 1991, and the 1992 Landers sequence are inverted for the state of stress. In all cases, the intermediate principal stress axis (S2) remained vertical, and changes in the state of stress consisted of variations in the trend of maximum and minimum principal stress axes (S1 and S3) and small variations in the value of the relative stress magnitudes (ϕ). In general, the stress state in the ECSZ has S1 trending east of north and ϕ = 0.43 to 0.65, suggesting that the ECSZ is a moderate stress refractor and the style of faulting is transtensional.

South of the Pinto Mountain fault, in the region of the 1992 Joshua Tree earthquake, the stress state determined from the 1981 to 1991 background seismicity changed on 23 April and again on 28 June 1992. In the central zone, S1 rotated from N14° ± 5°E to N28° ± 5°E on 23 April and back again to N16° ± 5°E on 28 June. Thus, the Landers mainshock in effect recharged some of the shear stress in the region of the Mw 6.1 Joshua Tree earthquke.

Comparison of the state of stress before and after 28 June 1992, along the Landers mainshock rupture zone, showed that the mainshock changed the stress orientation. The S1 trend rotated 7° to 20° clockwise and became progressively more fault normal from south to north. Along the Emerson-Camp Rock faults, the variation was so prominent that the focal mechanisms of aftershocks could not be fit by a single deviatoric stress tensor. The complex distribution of P and T axes suggests that most of the uniform component of the applied shear stress along the northern part of the rupture zone was released in the mainshock.

The San Bernardino Mountains region of the Mw 6.2 Big Bear earthquake has a distinctively different state of stress, as compared to the Landers region, with S1 trending N3° ± 5°W. This region did not show any significant change in the state of stress following the 1992 Mw 6.2 Big Bear sequence.
The 1991 Sierra Madre earthquake sequence in southern California: Seismological and tectonic analysis
Authors: Hauksson Egill
Published: September 2021

The (ML 5.8) Sierra Madre earthquake of 28 June 1991 occurred at a depth of 12 km under the San Gabriel Mountains of the central Transverse Ranges. Since at least 1932 this region had been quiescent for M ≧ 3. The mainshock focal mechanism derived from first-motion polarities exhibited almost pure thrust faulting, with a rake of 82° on a plane striking N62°E and dipping 50° to the north. The event appears to have occurred on the Clamshell-Sawpit fault, a splay of the Sierra Madre fault zone. The aftershock sequence following the mainshock occurred at a depth of 9 to 14 km and was deficient in small earthquakes, having a b value of 0.6. Twenty nine single-event focal mechanisms were determined for aftershocks of M > 1.5. The 4-km-long segment of the Clamshell-Sawpit fault that may have ruptured in the mainshock is outlined by several thrust focal mechanisms with an east-northeast-striking fault plane dipping to the north. To the west, several thrust aftershocks with east-striking nodal planes suggest some complexity in the aftershock faulting, such as a curved rupture surface. In addition, several strike-slip and normal faulting events occurred along the edges of the mainshock fault plane, indicating secondary tear faulting. The tectonic stress field driving the coexisting left-lateral strike-slip and thrust faults in the northern Los Angeles basin is north-south horizontal compression with vertical intermediate or minimum principal stress axis.
Initial investigation of site and topographic effects at Robinwood Ridge, California
Authors: Hartzell Stephen H. , Carver David L. , King Kenneth W.
Published: September 2021

Following the 1989 Loma Prieta earthquake, a dense array of seven digitally recorded, three-component seismograph stations was deployed on Robinwood Ridge 7.3 km northwest of the epicenter. The purpose of this array was to investigate the cause of high levels of structural damage and ground cracking observed on the ridge crest. Aftershocks recorded by the array allow a comparison of ground motion up the slope of the ridge from the base to the crest. The data present an extremely complicated pattern of ground motion that demonstrates the importance of the three-dimensionality of the problem. Slowness analysis of P wave trains show initial arrivals propagating away from the source with small angles of incidence and large apparent velocities, consistent with direct arrivals. After 0.5 sec, propagation azimuths become more random and apparent velocities drop, indicating nearly horizontal wave propagation and multiply reflected and diffracted phases within the ridge. Slowness analysis and particle motion diagrams of horizontal components of motion show dramatic variations in ground motion with changes in azimuth of the source and a complicated interaction between body waves and Rayleigh and Love waves. Results suggest that the larger amplitude, more coherent arrivals at the array stations favor a propagation direction parallel to the ridge axis. An amplification factor of from 1.5 to 4.5 is seen for frequencies from 1.0 to 3.0 Hz with wavelengths comparable to the base of the ridge, part of which may be caused by local site effects and part by topographic amplification. In addition, amplifications of up to a factor of 5 are seen at higher frequencies and are attributed to local site effects. These effects are most notable from 4 to 8 Hz on the vertical components, and from 6 to 9 Hz on the horizontal components. The entire Robinwood Ridge area may also have been situated in a region of heightened mainshock ground motion due to source directivity and radiation pattern effects.
Frequency-dependent attenuation of shear waves in the crust of the southern Kanto area, Japan
Authors: Kinoshita Shigeo
Published: September 2021

The attenuation characteristics of shear waves in the crust of the southern Kanto area, central Japan, were estimated using strong-motion data, including acceleration data recorded in the pre-Tertiary basement rocks by means of downhole observation. The quality factor Qs(f) was determined for a range of discrete frequencies from 0.5 to 16 Hz from the analysis of data from 13 local earthquakes with focal depths of less than about 50 km that occurred in the Philippine Sea plate and in the boundary zone between the lower part of the Eurasian plate and the upper part of the Philippine Sea plate. The estimated 1/Qs(f) shows a peaked structure in this frequency range on the assumption that the geometrical spreading exponent is -1 (body waves). The estimated peak 1/Qs(f) is of the order of 10-2 at 0.8 Hz.
A comparison of seismicity rates near Adak Island, Alaska, September 1988 through May 1990 with rates before the 1982 to 1986 apparent quiescence
Authors: Kisslinger Carl , Kindel Bruce
Published: September 2021

The rates of seismicity in the part of the Aleutian arc monitored by the Central Aleutians Seismic Network and in subregions of that zone during September 1988 through June 1990 have been compared with the rates during 1977 through 1981, 1981 through 1982, and 1983 through 1985. The purpose of the study was to determine whether the rate of earthquake occurrence had returned to the level observed before 1982, when a prolonged decrease in activity began. This decrease had been interpreted as seismic quiescence and was used as the basis of a prediction of a strong earthquake in this area. An MW = 8.0 earthquake did occur on 7 May 1986. The comparison with more recent activity is intended as one test of whether the observed decrease in activity was a real physical phenomenon or had been artificially produced by changes in network instrumentation or data-processing procedures. The only change in instrumentation since 1986 was the installation of a new digitizer, and tests were made to confirm that this new unit and the installation of new software for picking arrival times did not alter the completeness of detections or the magnitude values. The test cannot be completely definitive because aftershocks of the 1986 event were still in progress, according to the modified Omori fit to the data. The interval used is the latest possible because the network has been terminated. The 1988 to 1990 rates are similar to those in the prequiescence interval, but higher by an amount that is in qualitative agreement with the expected rate of continuing aftershocks. The rates in most of the zone are significantly higher than the rates during the period of decreased activity. Rates in the sites near the 1986 mainshock epicenter and the western termination of the 1986 rupture are higher than the pre-1982 rates, and indicate a concentration of the late aftershocks in these places. The results of the test support the conclusion that the 1982 to 1985 decrease in cataloged activity represents a real drop in the rate of seismicity prior to the 1986 earthquake. Examination of many more cases of seismicity changes before and following a strong earthquake is needed as the basis for judging the validity of quiescence as a true precursor. Another observation from recent seismicity is that an intense swarm in January 1989 and a magnitude mb = 6.1 event in March 1990 with a well-developed aftershock sequence have filled a spatial gap in the aftershocks of the 1986 event, near its epicenter.
Broadband waveform observation of the 28 June 1991 Sierra Madre earthquake sequence (ML = 5.8)
Authors: Ma Kuo-Fong , Kanamori Hiroo
Published: September 2021

The Sierra Madre earthquake (MI = 5.8) of 28 June 1991 occurred at a depth of about 12 km, on the Clamshell-Sawpit fault in the San Gabriel Mountains. High-quality seismograms were recorded with TERRAscope not only for the mainshock but also for the aftershocks at epicentral distances of about 16 km. We determined the focal mechanisms and seismic moments of the mainshock and 21 aftershocks by combining the waveform and first-motion data. We classified the events into five groups according to the location and waveforms recorded at PAS. Most events located within 5 km west of the mainshock are similar to the mainshock in waveform. The mechanisms thus determined are thrust mechanisms. A few events located east of the mainshock have waveforms different from the mainshock and have strike-slip mechanisms. The average Qβ values along the paths from the hypocenters of the Sierra Madre and the 3 December 1988 Pasadena earthquake (ML = 4.9) to PAS are about 130 and 80, respectively. The stress drop of the mainshock is about 500 bars. Most of the aftershocks have stress drops between 10 and 100 bars.
Seismic response of three-dimensional alluvial deposit with irregularities for incident wave motion from a point source
Authors: Kawano Masahiro , Matsuda Satoshi , Toyoda Kozo , Yamada Jun
Published: September 2021

The purpose of this article is to further investigate the influence of local site conditions of surface soil layers on seismic ground motion by studying the response of a semi-spherical alluvial deposit model under the more realistic type incident wave field. The incident wave field is a spherical wave radiated from a point source that is situated at the near focal distance and the far focal distance. A plane SH wavelet is also considered for comparison. A least-squares technique is applied to solve the boundary problem. The surface displacements on the alluvial deposit and in the elastic half-space are evaluated for various focal distances and source incidence angles. The numerical results indicate that there are significant differences concerning scattering and diffraction of wave motions between the two horizontal components when the semi-spherical alluvial deposit is subjected to incident wave motions from a point source. In the near field and for the component involving predominantly P and SV waves, the coupling of these waves induces a great variation in the spatial distributions, the amplitudes, and the time histories of the surface displacements compared to the tangential component, which involves mostly SH waves. The wave propagation characteristics of this component are very similar to those for a plane SH wavelet. In the far field and for the tangential component, there is not such strong coupling among waves. It is also shown that the first reflected waves at the curved boundary are deeply related to scattering and to diffraction of wave motion in a surface soil layer with irregularities and play an important role in the development of later arrivals.
Relationships between ocean bottom noise and the environment
Authors: Babcock Jeffrey M. , Kirkendall Barry A. , Orcutt John A.
Published: September 2021

Observations of ocean bottom low-frequency noise and surface environmental data over a period of 27 days in the northern Atlantic during the SAMSON and SWADE experiments reveal how closely related the noise is to meteorological conditions. Double-frequency microseisms produced by nonlinear interactions of storm-induced surface gravity waves are especially evident in the frequency band 0.16 to 0.3 Hz and show a high variability in both amplitude and peak frequencies. Bifurcated at times, the peak that characterizes the microseism band contains local and distant or “teleseismic” components, which are generated at different locations. Weather and storm fetch appear to be the major contributions to the size and shape of microseism spectra. Storm development on the sea surface is associated with progressively lower microseism frequencies along with a concurrent increase in amplitude. The single-frequency microseism peak is a continuous feature and is observed to portray the same time-dependent spectral characteristics as the portion of the double-frequency peak associated with distant storms. Coherence studies confirm that both peaks (single and teleseismic double) originate at a distant source. These peaks are generated at roughly the same location with some storm component over the coastline.
The rupture process and aftershock distribution of the 6 April 1992 MS 6.8 earthquake, Offshore British Columbia
Authors: Cassidy John F. , Rogers Garry C.
Published: September 2021

On 6 April 1992, a magnitude 6.8 (MS) earthquake occurred in the triple-junction region at the northern end of the Cascadia subduction zone. This was the largest earthquake in at least 75 yr to occur along the 110-km-long Revere-Dellwood-Wilson (RDW) transform fault and the first large earthquake in this region recorded by modern broadband digital seismic networks. It thus provides an opportunity to examine the rupture process along a young (<2 Ma) oceanic transform fault and to gain better insight into the tectonics of this triple-junction region. We have investigated the source parameters and the rupture process of this earthquake by modeling broadband body waves and long-period surface waves and by accurately locating the mainshock and the first 10 days of aftershocks using a well-located “calibration” event recorded during an ocean-bottom seismometer survey. Analysis of P and SH waveforms reveals that this was a complex rupture sequence consisting of three strike-slip subevents in 12 sec. The initial rupture occurred 5 to 6 km to the SW of the seafloor trace of the RDW fault at 50.55° N, 130.46° W. The dominant subevent occurred 2 to 3 sec later and 4.3 km beneath the seafloor trace of the RDW fault, and a third subevent occurred 5 sec later, 18 km to the NNW, suggesting a northwestward propagating rupture. The aftershock sequence extended along a 60- to 70-km-long segment of the RDW fault, with the bulk of the activity concentrated ∼30 to 40 km to the NNW of the epicenter, consistent with this interpretation. The well-constrained mechanism of the initial rupture (strike/dip/slip 339°/90°/−168°) and of the largest aftershock (165°/80°/170°) are rotated 15° to 20° clockwise relative to the seafloor trace of the RDW fault but are parallel to the Pacific/North America relative plate motion vector. In contrast, the mechanisms of the dominant subevent (326°/87°/−172°), and the long-period solution derived from surface waves aligns with the RDW fault. This suggests that small earthquakes (M < 6) in this area occur along faults that are optimally aligned with respect to the regional stress field, whereas large earthquakes, involving tens of kilometers of rupture, activate the RDW fault. For the mainshock, we estimate a seismic moment (from surface waves) of 1.0 × 1026 dyne-cm, a stress drop of 60 bars, and an average slip of 1.2 m. This represents only 21 yr of strain accumulation, implying that there is either a significant amount of aseismic slip along the RDW fault or that much of the strain accumulation manifests itself as deformation within the Dellwood and Winona blocks or along the continental margin.
Earthquake “Quanta” as an explanation for observed magnitudes and stress drops
Authors: Selwyn Sacks I. , Rydelek Paul A.
Published: September 2021

The familiar linear relation (Gutenberg-Richter) between the logarithm of the number of earthquakes and their magnitude is commonly ascribed to the distribution (fractal) of fault sizes in a self-similar process. We show that a concept of earthquake quanta whose failure is governed by simple physics and suggested by observations explains not only the Gutenberg-Richter relation but also the relatively constant stress drop for larger magnitude events. Results from computer simulation are consistent with observations from detailed seismicity studies.
Relationship between Liao and Clayton-Engquist absorbing boundary conditions: Acoustic case
Authors: Cheng Ningya , Cheng Chuen Hon
Published: September 2021

In this short note, we derive the differential form of Liao's multi-transmitting formula. The reflection coefficient of the multi-transmitting formula in the acoustic case is obtained in closed form. These formulas are compared with Clayton-Engquist absorbing boundary condition and are shown to have a very close relationship.
Propagation of high-frequency (4- to 50-Hz) P waves in the northeastern United States
Authors: Chael Eric P. , Leahy Patrick J. , Carter Jerry A. , Barstow Noël , Pomeroy Paul W.
Published: September 2021

We have measured the decay rate of high-frequency (4- to 50-Hz) P waves in the northeastern United States. We analyzed signals from 28 explosions of a 1988 USGS/AFGL/GSC refraction survey recorded at distances between 30 and 400 km. Over this range, the decay rate steadily increases from Δ−2 at 10 Hz to Δ−4 at 45 Hz. If one assumes geometric spreading of Δ−1.3, then the remaining decay is consistent with a nearly frequency-independent Q of about 1000. The results provide a useful parameterization for predicting P-wave spectra at near-regional ranges.
Comment on “A hybrid method for the estimation of ground motion in sedimentary basins: Quantitative modeling for Mexico City” by D. Fäh, P. Suhadolc, St. Mueller, and G. F. Panza
Authors: Zahradník Jiří
Published: September 2021

Two possible extensions of the commented article are suggested, with the aim to more efficiently couple the source and path simulation on one side, and the site-effect simulation on the other: (1) New excitation lines, surrounding the sedimentary basin, reduce the necessary size of the 2D finite-difference model of the site. They also better represent the 3D nature of the excitation, including the focal-mechanism effect. (2) New (2.5D approximate) equations of motion improve the way the 3D excitation is propagated within the 2D site model. The two suggested improvements can help in solving problems when a purely 2D treatment is oversimplified, but a true 3D treatment is too expensive.
Lateral variation in crustal structure of the northern Tibetan Plateau inferred from teleseismic receiver functions
Authors: Zhu Lupei , Owens Thomas J. , Randall George E.
Published: September 2021

We investigate lateral variations in crustal structure across the northern boundary of the Tibetan Plateau using the receiver functions at three broadband stations deployed during the 1991-1992 Tibet PASSCAL experiment. The first 5 sec of the receiver functions vary systematically with backazimuth: the radial receiver functions are symmetric across the N-S axis while the tangential receiver functions are antisymmetric across this axis. This symmetry can be modeled by E-W striking dipping interfaces in the upper-middle crust. The strike direction is consistent with the E-W trend of surface geology. Modeling a P-to-S converted phase in the receiver functions at each station suggests that there is a mid-crustal low-velocity layer with its upper boundary dipping 20° to 30° to the south. In addition, a shallow northward-dipping interface is responsible for the “double-peaked” direct P arrivals in the radial receiver functions and large tangential motions at one of the stations. The low-velocity layer, together with other geological and seismological observations, suggests that there is a hot, possibly partial melt zone in the middle crust of northern Tibet. Alternately, dipping velocity interfaces might be associated with some buried thrust faults in the upper crust that accommodated crust shortening during the plateau formation.
Numerical modeling of fault-zone trapped waves: Acoustic case
Authors: Huang Bor-Shouh , Teng Ta-liang , Yeh Yeong Tein
Published: September 2021

We have obtained numerical results for an acoustic wave propagating in a 3D medium with mixed boundary conditions. The specific model involves a vertical low-velocity fault zone of varying thickness embedded in an otherwise homogeneous half-space. At the fault-zone boundary, the stress and displacement are continuous; on the free surface, the stress is zero. A pseudo-spectrum method is employed to achieve sufficient resolution with reasonable computation time on a CRAY. Results show the development of guided waves trapped in the fault zone. These guided waves display large amplitudes and lengthening waveforms; they propagate at lower velocity with amplitudes that drop off mainly due to energy leakage out of the fault zone. As the width of the fault zone varies, the wave energy tends to funnel into the new low-velocity wave guide. At large distance, these guided waves become the dominant arrivals on seismograms. The waveforms are useful to recover the geometry and properties of the fault zone.