The Nature of Intrinsic Attenuation

2020 ◽  
Author(s):  
Yu-Chang Wu ◽  
Cheng-Ju Wu
Keyword(s):  
Seismic Waves ◽  
Body Waves ◽  
Northwestern Pacific ◽  
The Novel ◽  
Low Velocity ◽  
High Attenuation ◽  
Intrinsic Attenuation ◽  
Novel Method ◽  
The Difference ◽  
The Relationship

<p>Intrinsic attenuation plays an important role in investigating the interior structure of Earth, especially for the Lithosphere-asthenosphere system, the best place to understand the physical mechanics of plate tectonic. The dissipation, the high attenuation of seismic waves in the low-velocity zones, and the frequency dependence are the characteristic of intrinsic attenuation. However, N. Takeuchi, et al. measured the Northwestern Pacific Ocean’s lithosphere-asthenosphere system, and state the attenuation of the asthenosphere is 50 times larger than the attenuation of lithosphere attenuation. The attenuation of the lithosphere shows strong frequency dependency, but the attenuation of the asthenosphere does not. Previous theories of attenuation failed to explain this phenomenon. Here we demonstrate an explicit attenuation formulation to explain the high attenuation of seismic waves in the low-velocity zones and to show the mechanisms of spectral of teleseismic body waves rapidly fall off as frequency bigger than 1 Hz by perturbing the wave equation with the novel method we proposed. The result also indicates that the difference between the attenuation of the lithosphere and asthenosphere is because their attenuation governs by different physics mechanisms and mathematical models. Moreover, we illustrate the explicit formulation of the relationship between apparent t*, wave velocity, and frequency.</p>

scholarly journals Linear traveltime perturbation interpolation: a novel method to compute 3-D traveltimes

2015 ◽  
Vol 203 (1) ◽  
pp. 548-552 ◽  
Author(s):  
Jianzhong Zhang ◽  
Junjie Shi ◽  
Lin-Ping Song ◽  
Hua-wei Zhou
Keyword(s):  
Seismic Waves ◽  
Homogeneous Medium ◽  
Cell Boundary ◽  
Routine Method ◽  
Bilinear Interpolation ◽  
Linear Distribution ◽  
Heterogeneous Model ◽  
Computational Errors ◽  
Novel Method ◽  
The Difference

Abstract The linear traveltime interpolation has been a routine method to compute first arrivals of seismic waves and trace rays in complex media. The method assumes that traveltimes follow a linear distribution on each boundary of cells. The linearity assumption of traveltimes facilitates the numerical implementation but its violation may result in large computational errors. In this paper, we propose a new way to mitigate the potential shortcoming hidden in the linear traveltime interpolation. We use the vertex traveltimes in a calculated cell to introduce an equivalent homogeneous medium that is specific to the cell boundary from a source. Therefore, we can decompose the traveltime at a point on the cell boundary into two parts: (1) a reference traveltime propagating in the equivalent homogeneous medium and (2) a perturbation traveltime that is defined as the difference between the original and reference traveltimes. We now treat that the traveltime perturbation is linear along each boundary of cells instead of the traveltime. With the new assumption, we carry out the bilinear interpolation over traveltime perturbation to complete traveltime computation in a 3-D heterogeneous model. The numerical experiments show that the new method, the linear traveltime perturbation interpolation, is able to achieve much higher accuracy than that based on the linear traveltime interpolation.

scholarly journals Secondary Microseisms generated by typhoons in the Northwestern Pacific Ocean

2021 ◽  
Author(s):  
Nassima Benbelkacem ◽  
Eléonore Stutzmann ◽  
Martin Schimmel ◽  
Véronique Farra ◽  
Fabrice Ardhuin ◽  
...  
Keyword(s):  
Gravity Waves ◽  
Body Wave ◽  
Ocean Waves ◽  
Body Waves ◽  
Northwestern Pacific ◽  
Northwestern Pacific Ocean ◽  
Wave Reflections ◽  
Source Characteristics ◽  
Beamforming Technique ◽  
The Relationship

<p>Secondary Microseisms (SM) are recorded by seismometers in the period band 3-10 s. They are generated by the interaction of ocean gravity waves of similar frequencies and coming from nearly opposite directions. Typhoons create such ocean waves, and the purpose of this study is to investigate the relationship between typhoons and microseism source characteristics. We focused our study on the Northwestern Pacific and we analyzed seismic signals recorded by the Alaska array and the corresponding storm catalog. While P body waves enable to characterize the amplitude and the localization of the sources, secondary microseisms are dominated by surface waves. Therefore, we apply beamforming technique to the vertical components in order to highlight the weaker body wave signals. This analysis permits us to track the localization of SM sources every 6 hours. Our results show three cases: In the case of one active typhoon, the positions of SM sources are localized close to the typhoon position. In the case of two nearby typhoons acting simultaneously, the SM sources are localized in between the typhoons. Finally, when the typhoon arrives close to the coast, we observe sources generated by ocean wave reflections. In conclusion, the three mechanisms proposed by Ardhuin et al., (2011) are necessary to explain secondary microseisms generated by typhoons.</p>

Irving, John

2017 ◽  
Author(s):  
Laurie Champion
Keyword(s):  
Charles Dickens ◽  
Personal History ◽  
The Novel ◽  
John Irving ◽  
Look Back ◽  
The World ◽  
The Difference ◽  
Popular Novel ◽  
The Relationship ◽  
Looking Back

A major American writer, John Irving has published many novels, several of which have been adapted for film. His most popular novel is The World According to Garp, which has become both a popular and a cult classic. He is often compared to Charles Dickens, an author he admires. His novels are often political and take liberal views, confronting issues such as abortion rights, LGBT rights, and antiwar sentiments. His characters are not shy about sex and often begin sexual encounters at a young age. Major themes and subjects in his novels include the search for the father, the search for identity, looking back at one’s life, searching for one’s personal history, the difference between memory and truth, and unconventional lifestyles. The settings of his novels vary, and sometimes his characters travel both nationally and internationally. Many of his novels have been adapted for film, and he wrote screenplays for some of them. Irving became a household name in 1978, with the publication of The World According to Garp. Irving is well known for his dark sense of humor and sometimes absurd situations in which he places his characters. Many of his protagonists are older men who look back on their childhoods or adolescents who develop into men over the course of the novel. The relationship between memory and fact is often blurred as one’s memory of events trumps the actual events. Most of Irving’s protagonists are males who do not come from traditional families.

Determining Extrinsic Parameters for Active Stereovision

2009 ◽  
Vol 13 (2) ◽  
pp. 76-79 ◽  
Author(s):  
Huawei Wang ◽  
◽  
De Xu
Keyword(s):  
Least Squares ◽  
Rotational Axis ◽  
The Novel ◽  
Mapping Model ◽  
Least Squares Fitting ◽  
Marquardt Algorithm ◽  
Levenberg Marquardt ◽  
Extrinsic Parameters ◽  
Novel Method ◽  
The Relationship

In the novel method we propose for determining extrinsic parameters for active stereovision, we first map the relationship between rotational and yaw angles based on least squares fitting, then optimize the rotational axis between two cameras using the Levenberg-Marquardt algorithm. Extrinsic parameters are then easily derived for active stereovision based on the mapping model without complex recalibration. The results of experiments confirmed our proposed method's feasibility.

A Novel Global Optimization Algorithm and Its Application to Airfoil Optimization

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
B. Yang ◽  
Q. Xu ◽  
L. He ◽  
L. H. Zhao ◽  
Ch. G. Gu ◽  
...  
Keyword(s):  
Global Optimization ◽  
Optimization Algorithm ◽  
Fitness Function ◽  
Optimization Method ◽  
The Novel ◽  
Global Optimization Algorithm ◽  
Low Velocity ◽  
Airfoil Optimization ◽  
The Difference ◽  
Optimization Efficiency

In this paper, a novel global optimization algorithm has been developed, which is named as particle swarm optimization combined with particle generator (PSO–PG). In PSO–PG, a PG was introduced to iteratively generate the initial particles for PSO. Based on a series of comparable numerical experiments, it was convinced that the calculation accuracy of the new algorithm as well as its optimization efficiency was greatly improved in comparison with those of the standard PSO. It was also observed that the optimization results obtained from PSO–PG were almost independent of some critical coefficients employed in the algorithm. Additionally, the novel optimization algorithm was adopted in the airfoil optimization. A special fitness function was designed and its elements were carefully selected for the low-velocity airfoil. To testify the accuracy of the optimization method, the comparative experiments were also carried out to illustrate the difference of the aerodynamic performance between the optimized and its initial airfoil.

scholarly journals Language and the novel in globalization

2016 ◽  
Vol 11 (16) ◽  
Author(s):  
João Cavalcanti Nuto
Keyword(s):  
The Novel ◽  
Cultural Issues ◽  
Contemporary Novel ◽  
Ferdinand De Saussure ◽  
Structural Linguistics ◽  
Theory Of Language ◽  
The Difference ◽  
Relationship Of ◽  
Globalized World ◽  
The Relationship

This essay approaches linguistic and cultural issues associated with globalization, language and the novel in order to demonstrate how the novel as a literary genre can express the tensions of globalization. The main theoretical basis is Mikhail Bakhtin’s theory of language and the novel. Concerning language the paper recalls the discrepancy between the linguistic thought of Bakhtin’s circle and the structural linguistics by Ferdinand de Saussure, emphasizing that a linguistic based on utterance enables a suitable link between structural system and society. The paper explains the difference between centripetal and centrifugal forces of language, according to Bakhtin and their relationship with globalization. It also explains Bakhtin’s concept of the novel, stressing the relationship of the genre as a dialogic plurality of discourses, in order to demonstrate how suitable the novel is to express the globalized world. Theories of globalization are confronted and the problems related to globalization are exposed. Following Milton Santo’s thought, the paper refl ects on the possibility of another globalization, not only expansive, but also integrative. By commenting the cultural situation of certain writers and their attempts to express it, this essay combines Bakhtin’s thought with theories of globalization in order to point out possible responses of contemporary novel.

scholarly journals Observation of the long-period monotonic seismic waves of the November 11, 2018, Mayotte event by Iranian broadband seismic stations

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Hossein Sadeghi ◽  
Sadaomi Suzuki
Keyword(s):  
Surface Waves ◽  
Seismic Waves ◽  
Maximum Amplitude ◽  
Body Waves ◽  
Dipole Source ◽  
Arrival Times ◽  
Unusual Event ◽  
Long Period ◽  
Clear Peak ◽  
The Difference

AbstractOn November 11, 2018, an event generating long-lasting, monotonic long-period surface waves was observed by seismographs around the world. This event occurred at around 09:28 UTC east of the Mayotte Island, in the Indian Ocean off the coast of East Africa. This event is unusual due to the absence of body waves in the seismograms and no feeling of earth shaking by people locally. The purpose of this study is to investigate this unusual event using the waveforms recorded by 26 stations of the Iranian National Broadband Seismic Network. The stations are located at epicentral distances ranging from 4542 to 5772 km north-northeast of the event’s epicenter. The arrival of monochromatic long-period signals is visible around 10 UTC in the recordings of all the stations and the signals lasted for more than 30 min. Frequency analysis of the seismograms shows a clear peak at 0.064 Hz (15.6 s/cycle). The maximum amplitude of the transverse components is less than a half of the radial components. This is in agreement with the theoretical radiation pattern of Rayleigh and Love waves at a frequency of 0.06 Hz for a vertical compensated linear vector dipole source mechanism. The average apparent phase velocities were calculated as 3.31 and 2.97 km/s, in the transverse and radial directions, corresponding, respectively, to Love and Rayleigh waves in the frequency range of 0.05–0.07 Hz. A surface wave magnitude of Ms 5.07 ± 0.22 was estimated. Just before the monochromatic signal arrives, there is some dispersion in the surface waves. This observation may suggest a regular earthquake of Ms 4.3 ± 0.11 that triggered the November 11, 2018, event. The difference between the arrival times of the recorded surface waves of the two events is estimated to be less than 31 s, and most likely of ~ 7 s only.

Amplification of seismic body waves by low-velocity surface layers

1971 ◽  
Vol 61 (1) ◽  
pp. 109-145 ◽  
Author(s):  
J. R. Murphy ◽  
A. H. Davis ◽  
N. L. Weaver
Keyword(s):  
Seismic Waves ◽  
Dynamic Range ◽  
Repeated Measurements ◽  
Body Waves ◽  
Recording Site ◽  
Low Velocity ◽  
Frequency Dependent ◽  
Near Surface ◽  
Wide Range ◽  
Analytic Models

abstract Frequency-dependent amplification of seismic waves by near-surface low-velocity layers is a well-known phenomenon. This phenomenon was examined from both the analytic and experimental viewpoints for body waves (P, SV, SH). Groundmotion data, recorded in conjunction with the underground nuclear testing program at the Nevada Test Site, are used to provide experimental validation of the analytic models. Experimental amplification factors are derived from these data for a variety of recording-site near-surface geological configurations (alluvium, mine tailings, fill) and a wide dynamic range of ground-motion intensity (10−5 to 100 g). The variability in the mean amplification observed at a site for repeated measurements is described statistically. This analysis shows that, although the amplification at a given site varies on the average by a factor of about 1.4 across the frequency band of interest, from detonation to detonation, the frequency and magnitude of the dominant amplification are fairly consistent. The quality of the comparisons of the observed and calculated amplification indicates that the available linear analytic models are capable of describing the major features of the frequency-dependent amplification observed for this wide range of groundmotion intensity and recording-site geology.

scholarly journals Effects of Pasture Grass, Silage, and Hay Diet on Equine Fecal Microbiota

Animals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1330
Author(s):  
Yiping Zhu ◽  
Xuefan Wang ◽  
Liang Deng ◽  
Shulei Chen ◽  
Chunyan Zhu ◽  
...  
Keyword(s):  
Intestinal Microbiota ◽  
High Throughput Sequencing ◽  
Fecal Microbiota ◽  
The Novel ◽  
Intestinal Health ◽  
Pasture Grass ◽  
Grass Silage ◽  
Potential Impact ◽  
The Difference ◽  
The Relationship

Diet is an important factor affecting intestinal microbiota in horses. Fecal microbiota is commonly used as a substitute for studying hindgut microbiota when investigating the relationship between intestinal microbial changes and host health. So far, no study has compared the difference between the fecal microbiota found in horses that are fed pasture grass, silage, and hay. The present study aims to characterize the fecal microbiota in horses that were exclusively on one of the three forage diets, and to analyze the potential impact of these forages, especially silage, on horse intestinal health. There were 36 horses randomly assigned to each of the three groups; each group was fed only one type of forage for 8 weeks. High throughput sequencing was applied to analyze the bacterial taxa in fecal samples collected from the horses at the end of the feeding trial. The Lachnospiraceae family was statistically more abundant in horses fed with hay, while it was the least abundant in horses fed with silage. The Streptococcaceae spp., considered a core microbial component in equine intestinal microbiota, were present in significantly lower quantities in feces from horses that were fed pasture grass as compared to those from horses fed hay or silage. The novel data may help promote the balancing of horse intestinal microbiota and the maintenance of intestinal health in horses.

scholarly journals Literature and History: Study of Nigerian Indigenous Historical Novels

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Lere Adeyemi
Keyword(s):  
Party Politics ◽  
New Historicism ◽  
Historical Novels ◽  
The Novel ◽  
The Past ◽  
The World ◽  
Human Reality ◽  
History Of ◽  
The Difference ◽  
The Relationship

The assumption that history posits itself as a fact, while literature is to be taken as an artistic form, only for entertainment (i.e., the difference between truth and falsehood, reality and illusion) has long been debated by formalists and soclologlsts of literature. In Yoruba society, literature and history are im­portant in explaining the fullness of life and the world around us. It is against this background that this paper examines the relationship between literature and history and how Yoruba novelists use their works as vehicles for the repre­sentation of history. We adopt the theory of New Historicism to analyze T.A.A. Ladele's lgbi Aye n yi and Olu Owolabi's Ote Nibo. Some of the findings reveal that: both Yoruba literature and history are closely related, they are both based on Yoruba experience and Yoruba existence either in the past or present; while Ladele Interprets the history of the dignity and royal glamour of the Yoruba oba in the precolonial era as a form of domination which is often achieved through culturally-orchestrated consent rather than force; Owolabi represents the hlstory of party politics in Yoruba society as fraudulent, deceltful, full of bitterness and violence. The paper concludes that both novelists are subjective in their representation of Yoruba history, but they successfully establfsh the fact that the novel is a repository of history; however, such history is not a mere chronlcle of facts and events, but rather a complex description of human reality and a challenge to the preconceived notions of the societies from which they emerged.

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