Structure and mobility of the crust and mantle in the vicinity of island arcs

1968 ◽  
Vol 5 (4) ◽  
pp. 985-991 ◽  
Author(s):  
Jack Oliver ◽  
Bryan Isacks
Keyword(s):  
Upper Mantle ◽  
Seismic Waves ◽  
Current Knowledge ◽  
Average Rate ◽  
Seismic Wave Propagation ◽  
Rift System ◽  
Island Arcs ◽  
Deep Earthquake ◽  
Anomalous Zone ◽  
The World

A detailed study of seismic wave propagation in the Fiji-Tonga region shows that there exists in the upper mantle an anomalous zone whose thickness is about 100 km and whose upper surface is approximately defined by the zone of seismic foci extending to depths of about 700 km. Attenuation of seismic waves within the zone is anomalously low and velocities are high. Other island arcs appear to be associated with similar zones.The anomalous zone in Tonga can be interpreted as the westernmost portion of a block of lithosphere that has been thrust, or dragged, or has settled beneath the island arc. Such mobility of the lithosphere suggests a key role in geotectonics for this layer of strength and raises a number of possible new solutions to long standing problems. For example, assuming that deep earthquake zones throughout the world are a measure of the amount of underthrusting during the last 107 years, an average rate of spreading over the entire worldwide rift system can be obtained as a check, but not a proof, of the hypothesis. The half-velocity obtained is 1.3 cm/year and is reasonable in light of current knowledge.

scholarly journals P Wave Amplitude Decay Offers a Glimpse of Earth's Structure

Eos ◽  
2016 ◽  
Vol 97 ◽  
Author(s):  
Lily Strelich
Keyword(s):  
United States ◽  
Upper Mantle ◽  
Seismic Waves ◽  
Wave Amplitude ◽  
The United States ◽  
Deep Earthquake

Scientists look at deep earthquake signals to map how seismic waves lose energy in the upper mantle across the United States.

scholarly journals A Comprehensive Review of the Ethnotraditional Uses and Biological and Pharmacological Potential of the Genus Mimosa

2021 ◽  
Vol 22 (14) ◽  
pp. 7463
Author(s):  
Ismat Majeed ◽  
Komal Rizwan ◽  
Ambreen Ashar ◽  
Tahir Rasheed ◽  
Ryszard Amarowicz ◽  
...  
Keyword(s):  
Web Of Science ◽  
Scientific Literature ◽  
Therapeutic Potential ◽  
Current Knowledge ◽  
Folk Medicine ◽  
Nutritional Values ◽  
Biological Potential ◽  
The World ◽  
The Future ◽  
Pharmacological Potential

The Mimosa genus belongs to the Fabaceae family of legumes and consists of about 400 species distributed all over the world. The growth forms of plants belonging to the Mimosa genus range from herbs to trees. Several species of this genus play important roles in folk medicine. In this review, we aimed to present the current knowledge of the ethnogeographical distribution, ethnotraditional uses, nutritional values, pharmaceutical potential, and toxicity of the genus Mimosa to facilitate the exploitation of its therapeutic potential for the treatment of human ailments. The present paper consists of a systematic overview of the scientific literature relating to the genus Mimosa published between 1931 and 2020, which was achieved by consulting various databases (Science Direct, Francis and Taylor, Scopus, Google Scholar, PubMed, SciELO, Web of Science, SciFinder, Wiley, Springer, Google, The Plant Database). More than 160 research articles were included in this review regarding the Mimosa genus. Mimosa species are nutritionally very important and several species are used as feed for different varieties of chickens. Studies regarding their biological potential have shown that species of the Mimosa genus have promising pharmacological properties, including antimicrobial, antioxidant, anticancer, antidiabetic, wound-healing, hypolipidemic, anti-inflammatory, hepatoprotective, antinociceptive, antiepileptic, neuropharmacological, toxicological, antiallergic, antihyperurisemic, larvicidal, antiparasitic, molluscicidal, antimutagenic, genotoxic, teratogenic, antispasmolytic, antiviral, and antivenom activities. The findings regarding the genus Mimosa suggest that this genus could be the future of the medicinal industry for the treatment of various diseases, although in the future more research should be carried out to explore its ethnopharmacological, toxicological, and nutritional attributes.

scholarly journals 405 - Music Therapy in the management of dementia

2020 ◽  
Vol 32 (S1) ◽  
pp. 121-121
Author(s):  
Catarina Pedro ◽  
Beatriz Jorge ◽  
Mariana Duarte
Keyword(s):  
Cognitive Function ◽  
Music Therapy ◽  
Behavioral Problems ◽  
Positive Impact ◽  
Current Knowledge ◽  
Neuropsychiatric Symptoms ◽  
World Health ◽  
Psychotic Symptoms ◽  
The World ◽  
Health Organization

Introduction:Dementia has become a worldwide concern. According to the World Health Organization, there are 50 million individuals suffering from dementia across the world and approximately 20 million new cases are diagnosed each year. The efficacy of medications in controlling agitation and psychotic symptoms is modest and may cause serious adverse effects, outlining the urge for new treatment methods for patients with dementia. Music therapy (MT) is a nonpharmacologic strategy that is used in patients with early-to-late stages of dementia with promising results.Objectives:The aim of this presentation is to evaluate the benefits of music therapy in cognitive functioning and neuropsychiatric symptoms in patients diagnosed with dementia. We also summarize the current knowledge about this topic.Methods:A non-systematic review of the literature was performed on PubMed, PsycINFO and Web of science using selected keywords.Results:MT sustains its benefit because musical memory regions in the brain are relatively spared compared to cognitive function. “Musical memories” can, thus, be stored longer than non-musical memories, allowing to recall associated life events and emotions. Systematic reviews suggest that MT seem to have a positive effect on symptoms such as depression, anxiety and behavioral problems while the findings concerning agitation/aggression are inconsistent. No large differences were found between studies using live or recorded music although the latter reported more of a consistently positive impact on behavioral and psychological outcomes. The studies using live music, however, reported specific benefits to relationships and interactions.Conclusions:The majority of the studies have methodological limitations, making it difficult to offer firm conclusions. Despite this, there were positive results on aspects of quality of life, cognitive function, behavioral, psychological, physiological and communication outcomes.

scholarly journals Cellular and Molecular Players in the Interplay between Adipose Tissue and Breast Cancer

2021 ◽  
Vol 22 (3) ◽  
pp. 1359
Author(s):  
Francesca Reggiani ◽  
Paolo Falvo ◽  
Francesco Bertolini
Keyword(s):  
Breast Cancer ◽  
Adipose Tissue ◽  
Metabolic Disorders ◽  
Current Knowledge ◽  
Therapeutic Interventions ◽  
Preclinical Research ◽  
The World ◽  
Adipose Cells

The incidence and severity of obesity are rising in most of the world. In addition to metabolic disorders, obesity is associated with an increase in the incidence and severity of a variety of types of cancer, including breast cancer (BC). The bidirectional interaction between BC and adipose cells has been deeply investigated, although the molecular and cellular players involved in these mechanisms are far from being fully elucidated. Here, we review the current knowledge on these interactions and describe how preclinical research might be used to clarify the effects of obesity over BC progression and morbidity, with particular attention paid to promising therapeutic interventions.

Transverse isotropy of the upper mantle in the vicinity of Pacific fracture zones

1969 ◽  
Vol 59 (1) ◽  
pp. 59-72
Author(s):  
Robert S. Crosson ◽  
Nikolas I. Christensen
Keyword(s):  
Upper Mantle ◽  
Symmetry Axis ◽  
Transverse Isotropy ◽  
Transversely Isotropic ◽  
Seismic Wave Propagation ◽  
Fracture Zones ◽  
Mantle Material ◽  
Transversely Isotropic Media ◽  
Horizontal Symmetry ◽  
Isotropic Media

Abstract Several recent investigations suggest that portions of the Earth's upper mantle behave anisotropically to seismic wave propagation. Since several types of anisotropy can produce azimuthal variations in Pn velocities, it is of particular geophysical interest to provide a framework for the recognition of the form or forms of anisotropy most likely to be manifest in the upper mantle. In this paper upper mantle material is assumed to possess the elastic properties of transversely isotropic media. Equations are presented which relate azimuthal variations in Pn velocities to the direction and angle of tilt of the symmetry axis of a transversely isotropic upper mantle. It is shown that the velocity data of Raitt and Shor taken near the Mendocino and Molokai fracture zones can be adequately explained by the assumption of transverse isotropy with a nearly horizontal symmetry axis.

scholarly journals Seismic wave propagation in anisotropic ice – Part 1: Elasticity tensor and derived quantities from ice-core properties

2015 ◽  
Vol 9 (1) ◽  
pp. 367-384 ◽  
Author(s):  
A. Diez ◽  
O. Eisen
Keyword(s):  
Seismic Waves ◽  
Dynamic Behaviour ◽  
Ice Core ◽  
Ice Cores ◽  
Seismic Wave Propagation ◽  
Elasticity Tensor ◽  
Reflection Coefficients ◽  
Seismic Velocities ◽  
Crystal Anisotropy ◽  
Elasticity Tensors

Abstract. A preferred orientation of the anisotropic ice crystals influences the viscosity of the ice bulk and the dynamic behaviour of glaciers and ice sheets. Knowledge about the distribution of crystal anisotropy is mainly provided by crystal orientation fabric (COF) data from ice cores. However, the developed anisotropic fabric influences not only the flow behaviour of ice but also the propagation of seismic waves. Two effects are important: (i) sudden changes in COF lead to englacial reflections, and (ii) the anisotropic fabric induces an angle dependency on the seismic velocities and, thus, recorded travel times. A framework is presented here to connect COF data from ice cores with the elasticity tensor to determine seismic velocities and reflection coefficients for cone and girdle fabrics. We connect the microscopic anisotropy of the crystals with the macroscopic anisotropy of the ice mass, observable with seismic methods. Elasticity tensors for different fabrics are calculated and used to investigate the influence of the anisotropic ice fabric on seismic velocities and reflection coefficients, englacially as well as for the ice–bed contact. Hence, it is possible to remotely determine the bulk ice anisotropy.

scholarly journals Seismic anisotropy: an original tool to understand the geodynamic evolution of the Italian peninsula

1997 ◽  
Vol 40 (3) ◽  
Author(s):  
L. Margheriti ◽  
C. Nostro ◽  
A. Amato ◽  
M. Cocco
Keyword(s):  
Upper Mantle ◽  
Common Property ◽  
Seismic Waves ◽  
Seismic Anisotropy ◽  
Structural Features ◽  
Relative Strength ◽  
Plate Motion ◽  
Mantle Minerals ◽  
Anisotropic Bodies ◽  
Shallow Crust

Anisotropy is a common property of the Earth's crust and the upper mantle; it is related to the strain field of the medium and therefore to geodynamics. In this paper we describe the different possible origins of anisotropic behavior of the seismic waves and the seismological techniques used to define anisotropic bodies. In general it is found that the fast polarization direction is parallel to the absolute plate motion in cratonic areas, to the spreading direction near rifts or extensional zones, and to the main structural features in transpressive regimes. The delay times between fast and slow waves reflect the relative strength and penetration at depth of the deformation field. The correspondence between surface structural trends and anisotropy in the upper mantle, found in many regions of the world, strongly suggest that orogenic processes involve not only the shallow crust but the entire lithosphere. Recently in Italy both shear wave splitting analysis and Pn inversion were applied to define the trend of seismic anisotropy. Along the Northern Appeninic arc fast directions follow the strike of the arc (i.e., parallel to the strike of the Miocene-Pleistocene compressional features), whereas in the Tyrrhenian zone fast directions are about E-W SW-NE; parallel to the post-Miocene extension that is thought to have reoriented the mantle minerals fabric in the astenosphere.

scholarly journals Vertical to Horizontal Spectral Ratio (VHSR) Response of Seismic Wave Propagation in a Homogeneous Elastic – Poroelastic Medium Using The Spectral Finite Element Method

2021 ◽  
Vol 11 (1) ◽  
pp. 95
Author(s):  
Sudarmaji Saroji ◽  
Budi Eka Nurcahya ◽  
Nivan Ramadhan Sugiantoro
Keyword(s):  
Finite Element Method ◽  
Elastic Medium ◽  
Seismic Waves ◽  
Low Frequency ◽  
Seismic Wave Propagation ◽  
P Wave ◽  
Poroelastic Medium ◽  
Compressional Waves ◽  
Spectral Finite Element Method ◽  
Spectral Finite Element

<p>Numerical modeling of 2D seismic wave propagation using spectral finite element method to estimate the response of seismic waves passing through the poroelastic medium from a hydrocarbon reservoir has been carried out. A hybrid simple model of the elastic - poroelastic - elastic with a mesoscopic scale element size of about 50cm was created. Seismic waves which was in the form of the ricker function are generated on the first elastic medium, propagated into the poroelastic medium and then transmitted to the second elastic medium. Pororoelastic medium is bearing hydrocarbon fluid in the form of gas, oil or water. Vertical and horizontal component of velocity seismograms are recorded on all mediums. Seismograms which are recorded in the poroelastic and second elastic medium show the existence of slow P compressional waves following fast P compressional waves that do not appear on the seismogram of the first elastic medium. The slow P wave is generated when the fast P wave enters the interface of the elastic - poroelastic boundary, propagated in the poroelastic medium and is transmited to the second elastic medium. The curves of Vertical to horizontal spectrum ratio (VHSR) which are observed from seismograms recorded in the poroelastic and the second elastic medium show that the peak of VHSR values at low frequency correlated with the fluid of poroelastic reservoir. The highest VHSR value at the low frequency which is recorded on the seismogram is above the 2.5 Hz frequency for reservoirs containing gas and oil in the second elastic medium, while for the medium containing water is the highest VHSR value is below the 2.5 Hz frequency.</p>

A Study of Seismic Wave Propagation at Regional Distances in Five Areas of the World

1982 ◽  
Author(s):  
Z. A. Der ◽  
A. O'Donnell ◽  
T. W. McElfresh ◽  
R. Jutila ◽  
J. A. Burnetti
Keyword(s):  
Wave Propagation ◽  
Seismic Wave ◽  
Seismic Wave Propagation ◽  
The World
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