Статті в журналах: "Rayleigh anomalies"

1

Gao, Hongtao, Wei Yan, Song Hu, and Yudong Zhang. "Eliminating the Rayleigh anomalies in metal grating." Optics Communications 405 (December 2017): 8–11. http://dx.doi.org/10.1016/j.optcom.2017.07.062.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

2

van der Lee, S. "Observations and origin of Rayleigh-wave amplitude anomalies." Geophysical Journal International 135, no. 2 (November 1998): 691–99. http://dx.doi.org/10.1046/j.1365-246x.1998.00678.x.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

3

Savoia, Silvio, Armando Ricciardi, Alessio Crescitelli, Carmine Granata, Emanuela Esposito, Vincenzo Galdi, and Andrea Cusano. "Surface sensitivity of Rayleigh anomalies in metallic nanogratings." Optics Express 21, no. 20 (September 26, 2013): 23531. http://dx.doi.org/10.1364/oe.21.023531.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

4

Schreier, Frank, and Olof Bryngdahl. "Confined wave packets in the domain of Rayleigh–Wood anomalies." Journal of the Optical Society of America A 17, no. 1 (January 1, 2000): 68. http://dx.doi.org/10.1364/josaa.17.000068.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

5

Hara, Tatsuhiko, and Robert J. Geller. "Anomalously large near-field Rayleight waves excited by the 1992 Landers, California, earthquake." Bulletin of the Seismological Society of America 84, no. 3 (June 1, 1994): 751–60. http://dx.doi.org/10.1785/bssa0840030751.

Повний текст джерела

Анотація:

Abstract The epicenter of the Landers, California, earthquake (28 June 1992; MW = 7.3) was located near the TERRAscope network of broadband seismic stations. The direct Rayleigh wave arrivals, R1, were clipped, and the first two later arrivals, R2 and R3, were contaminated by the waves from a large aftershock, but, as reported by Kanamori et al. (1992a), the amplitudes of R4 and later great circle Rayleigh wave arrivals (fundamental mode spheroidal free oscillations) are about 10 times larger than predicted by synthetic seismograms for a spherically symmetric earth model. We show that, for the moment tensor of the Landers event (predominantly vertical strike slip), the amplitudes of synthetics at the TERRAscope stations for a laterally heterogeneous, rotating, elliptical model are about 10 times greater than those for a spherically symmetric model. Because the anomaly ratio is sensitive to both the source model and the three-dimensional (3D) earth model, we do not attempt to reproduce the exact anomaly ratios recorded by the various stations. To explain the existence of near-field amplitude anomalies in general, we use the first-order Born approximation to find the perturbation to the synthetic seismogram resulting from lateral heterogeneity, ellipticity, and the earth's rotation. In a coordinate system with the source on the z axis a point-source strike-slip earthquake on a vertical fault plane in a spherically symmetric medium excites Rayleigh waves with azimuthal order ±2 only; these waves have a near-field vertical displacement of zero at the source; the displacement increases with the square of epicentral distance for any given azimuth. Coupling as a result of asphericity allows such a source to excite Rayleigh waves with azimuthal order zero, whose near-field amplitude is independent of epicentral distance, thereby generating large near-field amplitude anomalies. We conduct numerical experiments to study the influence of various parameters on near-field amplitude anomalies.

Стилі APA, Harvard, Vancouver, ISO та ін.

6

Mo, Ruping. "On Adding Thermodynamic Damping Mechanisms to Refine Two Classical Models of Katabatic Winds." Journal of the Atmospheric Sciences 70, no. 7 (July 1, 2013): 2325–34. http://dx.doi.org/10.1175/jas-d-12-0256.1.

Повний текст джерела

Анотація:

Abstract The Prandtl and layer-averaged models of katabatic winds contain some nonphysical singularities in the analytical solutions, which give unbounded steady flow anomalies at zero slope angles or adiabatic lapse rates. This study presents some simple refinements of these two classical models, in which the aforementioned singularities are removed when Newtonian cooling and Rayleigh friction are included in the system. It is pointed out that, in the limit of zero slope angles or adiabatic lapse rates, the along-slope buoyancy force and the adiabatic heating caused by air descending approach zero. Under such circumstances, a bounded steady solution for the katabatic winds is impossible unless some damping mechanisms are included to retard the anomalies induced by the radiative cooling effect in the boundary layer. Newtonian cooling and Rayleigh friction are the two simplest thermodynamic damping mechanisms that can be included to balance the effects of eddy viscosity and eddy thermal conductivity in the katabatic-flow model. Physically speaking, the Newtonian cooling term represents a small partition of the radiative effect and the Rayleigh friction term represents an approximation of the bottom drag effect in a turbulent boundary layer.

Стилі APA, Harvard, Vancouver, ISO та ін.

7

Kolkowski, Radoslaw, and A. Femius Koenderink. "Gain-induced scattering anomalies of diffractive metasurfaces." Nanophotonics 9, no. 14 (July 26, 2020): 4273–85. http://dx.doi.org/10.1515/nanoph-2020-0253.

Повний текст джерела

Анотація:

AbstractPhotonic nanostructures with gain and loss have long been of interest in the context of diverse scattering anomalies and light-shaping phenomena. Here, we investigate the scattering coefficients of simple gain-doped diffractive metasurfaces, revealing pairs of scattering anomalies surrounded by phase vortices in frequency–momentum space. These result from an interplay between resonant gain, radiative loss, and interference effects in the vicinity of Rayleigh anomalies. We find similar vortices and singular points of giant amplification in angle-resolved reflectivity spectra of prism-coupled gain slabs. Our findings could be of interest for gain-induced wavefront shaping by all-dielectric metasurfaces, possibly employing gain coefficients as low as ∼50 cm−1.

Стилі APA, Harvard, Vancouver, ISO та ін.

8

Cui, Yan, and Yanfei Wang. "Velocity modeling based on Rayleigh wave dispersion curve and sparse optimization inversion." Inverse Problems & Imaging 15, no. 5 (2021): 1121. http://dx.doi.org/10.3934/ipi.2021031.

Повний текст джерела

Анотація:

<p style='text-indent:20px;'>This paper studies the S wave velocity modeling based on the Rayleigh wave dispersion curve inversion. We first discuss the forward simulation, and present a fast root-finding method with cubic-order of convergence speed to obtain the Rayleigh wave dispersion curve. With the Rayleigh wave dispersion curve as the observation data, and considering the prior geological anomalies structural information, we establish a sparse constraint regularization model, and propose an iterative solution method to solve for the S wave velocity. Experimental tests are performed both on the theoretical models and on the field data. It indicates from the experimental results that our new inversion scheme possesses the characteristics of easy calculation, high computational efficiency and high precision for model characterization.</p>

Стилі APA, Harvard, Vancouver, ISO та ін.

9

Darweesh, Ahmad, Stephen Bauman, Desalegn Debu, and Joseph Herzog. "The Role of Rayleigh-Wood Anomalies and Surface Plasmons in Optical Enhancement for Nano-Gratings." Nanomaterials 8, no. 10 (October 9, 2018): 809. http://dx.doi.org/10.3390/nano8100809.

Повний текст джерела

Анотація:

We propose and report on the design of a 1-D metallo-dielectric nano-grating on a GaAs substrate. We numerically study the impact of grating period, slit and wire widths, and irradiating angle of incidence on the optical response. The optimal wire width, w = 160 nm, was chosen based on previous results from investigations into the influence of wire width and nano-slit dimensions on optical and electrical enhancements in metal-semiconductor-metal photodetectors. In this present project, resonant absorption and reflection modes were observed while varying the wire and nano-slit widths to study the unique optical modes generated by Rayleigh-Wood anomalies and surface plasmon polaritons. We observed sharp and diffuse changes in optical response to these anomalies, which may potentially be useful in applications such as photo-sensing and photodetectors. Additionally, we found that varying the slit width produced sharper, more intense anomalies in the optical spectrum than varying the wire width.

Стилі APA, Harvard, Vancouver, ISO та ін.

10

Bado, Mattia, Joan Casas, and António Barrias. "Performance of Rayleigh-Based Distributed Optical Fiber Sensors Bonded to Reinforcing Bars in Bending." Sensors 18, no. 9 (September 16, 2018): 3125. http://dx.doi.org/10.3390/s18093125.

Повний текст джерела

Анотація:

Distributed Optical Fiber Sensors (DOFSs), thanks to their multiple sensing points, are ideal tools for the detection of deformations and cracking in reinforced concrete (RC) structures, crucial as a means to ensure the safety of infrastructures. Yet, beyond a certain point of most DOFS-monitored experimental tests, researchers have come across unrealistic readings of strain which prevent the extraction of further reliable data. The present paper outlines the results obtained through an experimental test aimed at inducing such anomalies to isolate and identify the physical cause of their origin. The understanding of such a phenomenon would enable DOFS to become a truly performant strain sensing technique. The test consists of gradually bending seven steel reinforcement bars with a bonded DOFS under different conditions such as different load types, bonding adhesives, bar sections and more. The results show the bonding adhesives having an influence on the DOFS performance but not on the rise of anomalies while the reasons triggering the latter are narrowed down from six to two, reaching a strain threshold and a change in structure’s deformative behavior. Further planned research will allow identification of the cause behind the rise of strain-reading anomalies.

Стилі APA, Harvard, Vancouver, ISO та ін.

11

Harvey, James E., and Richard N. Pfisterer. "Understanding diffraction grating behavior: including conical diffraction and Rayleigh anomalies from transmission gratings." Optical Engineering 58, no. 08 (August 28, 2019): 1. http://dx.doi.org/10.1117/1.oe.58.8.087105.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

12

Pettersen, Øyvind, and Valérie Maupin. "Lithospheric anisotropy on the Kerguelen hotspot track inferred from Rayleigh wave polarisation anomalies." Geophysical Journal International 149, no. 1 (April 2002): 225–46. http://dx.doi.org/10.1046/j.1365-246x.2002.01646.x.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

13

Huang, Tzu-Ying, Yuancheng Gung, Wen-Tzong Liang, Ling-Yun Chiao, and Louis S. Teng. "Broad-band Rayleigh wave tomography of Taiwan and its implications on gravity anomalies." Geophysical Research Letters 39, no. 5 (March 2012): n/a. http://dx.doi.org/10.1029/2011gl050727.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

14

Skigin, Diana C., and Marcelo Lester. "Enhanced transmission via evanescent-to-propagating conversion in metallic nanoslits: role of Rayleigh anomalies." Journal of Optics 16, no. 4 (March 19, 2014): 045004. http://dx.doi.org/10.1088/2040-8978/16/4/045004.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

15

Molnar, Peter, and Gregory A. Houseman. "Rayleigh-Taylor instability, lithospheric dynamics, surface topography at convergent mountain belts, and gravity anomalies." Journal of Geophysical Research: Solid Earth 118, no. 5 (May 2013): 2544–57. http://dx.doi.org/10.1002/jgrb.50203.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

16

Zhang, X., K. Cao, J. Li, X. B. Sun, Y. Y. Wang, Y. Li, X. Zhang, and X. H. Kong. "Engineered polar magneto-optical Kerr rotation through Wood–Rayleigh anomalies and magnetoplamon resonance coupling." OSA Continuum 2, no. 1 (December 17, 2018): 1. http://dx.doi.org/10.1364/osac.2.000001.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

17

Li, Dong, Gaofang Li, Hui Kong, Shiwei Shu, Guohong Ma, Jin Ge, Shuhong Hu, and Ning Dai. "The Extraordinary Transmission Spectrum in Terahertz Regime: Combination of Shape Resonances and Rayleigh anomalies." Journal of Infrared, Millimeter, and Terahertz Waves 33, no. 2 (January 8, 2012): 212–17. http://dx.doi.org/10.1007/s10762-011-9868-4.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

18

Lakhtakia, A., V. K. Varadan, and V. V. Varadan. "The Acoustic Response of a Periodically Rough Elastic Plate (Ice) in Contact With Water." Journal of Applied Mechanics 52, no. 1 (March 1, 1985): 144–48. http://dx.doi.org/10.1115/1.3168985.

Повний текст джерела

Анотація:

The plane wave scattering matrix theory is applied to formulate a T-matrix which characterizes the acoustic response of an infinite solid plate bounded by semi-infinite vacuum and fluid half spaces on either side. Individual T-matrices for the periodically rough vacuum/solid and solid/fluid interfaces are used in this derivation. Using the computed results, the anomalies in the scattering response of the rough solid plate are explained in terms of the Rayleigh, the Scholte, and the Lamb waves.

Стилі APA, Harvard, Vancouver, ISO та ін.

19

Liu, Xin, and Dapeng Zhao. "Seismic evidence for a plume-modified oceanic lithosphere–asthenosphere system beneath Cape Verde." Geophysical Journal International 225, no. 2 (January 11, 2021): 872–86. http://dx.doi.org/10.1093/gji/ggab012.

Повний текст джерела

Анотація:

SUMMARY We determine a new 3-D shear wave velocity (Vs) model down to 400 km depth beneath the Cape Verde hotspot that is far from plate boundaries. This Vs model is obtained by using a new method of jointly inverting P- and S-wave receiver functions, Rayleigh-wave phase-velocity data and S-wave arrival times of teleseismic events. Two Vs discontinuities at ∼15 and ∼60 km depths are revealed beneath volcanic islands, which are interpreted as the Moho discontinuity and the Gutenberg (G) discontinuity. Between the north and south islands, obvious high-Vs anomalies exist in the uppermost mantle down to a depth of ∼100–150 km beneath the Atlantic Ocean, whereas obvious low-Vs anomalies exist in the uppermost mantle beneath the volcanic islands including the active Fogo volcano. These low-Vs anomalies merge into a significant column-like low-Vs zone at depths of ∼150–400 km beneath the Cape Verde swell. We propose that these features in the upper mantle reflect a plume-modified oceanic lithosphere–asthenosphere system beneath the Cape Verde hotspot.

Стилі APA, Harvard, Vancouver, ISO та ін.

20

Schwenk, J. Tyler, Steven D. Sloan, Julian Ivanov, and Richard D. Miller. "Surface-wave methods for anomaly detection." GEOPHYSICS 81, no. 4 (July 2016): EN29—EN42. http://dx.doi.org/10.1190/geo2015-0356.1.

Повний текст джерела

Анотація:

Perimeter-defense operations, geohazard assessment, and engineering characterization require the detection and localization of subsurface anomalies. Seismic waves incident upon these discontinuities generate a scattered wavefield. We have developed various surface-wave techniques, currently being fielded, that have consistently delivered accurate and precise results across a wide range of survey parameters and geographical locations. We use the multichannel analysis of surface waves approach to study the multimode Rayleigh wave, the backscatter analysis of surface waves (BASW) method to detect anomalies, 3D visualization for efficient seismic interpretation, BASW correlation for attribute analysis, and instantaneous-amplitude integration in the complex BASW method. Discrete linear moveout functions and [Formula: see text]-[Formula: see text] filter designs are optimized for BASW considering the fundamental and higher mode dispersion trends of the Rayleigh wave. Synthetic and field data were used to demonstrate multimode BASW and mode separation, which accentuated individual scatter events, and ultimately increased confidence in points of interest. Simple correlation algorithms between fundamental and higher-mode BASW data offer attribute analysis that limits the subjective interpretation of BASW images. Domain sorting and Hilbert transforms allow for 3D visualization and rapid interpretation of an anomaly’s wavefield phenomena within an amplitude cube. Furthermore, instantaneous-amplitude analysis can be incorporated into a more robust complex BASW method that forgives velocity-estimation inaccuracies, while requiring less rigorous preprocessing. Our investigations have suggested that a multifaceted surface-wave analysis provides a valuable tool for today’s geophysicists to fulfill anomaly-detection survey requirements.

Стилі APA, Harvard, Vancouver, ISO та ін.

21

Qorbani, Ehsan, Dimitri Zigone, Mark R. Handy, and Götz Bokelmann. "Crustal structures beneath the Eastern and Southern Alps from ambient noise tomography." Solid Earth 11, no. 5 (October 29, 2020): 1947–68. http://dx.doi.org/10.5194/se-11-1947-2020.

Повний текст джерела

Анотація:

Abstract. We study the crustal structure under the Eastern and Southern Alps using ambient noise tomography. We use cross-correlations of ambient seismic noise between pairs of 71 permanent stations and 19 stations of the Eastern Alpine Seismic Investigation (EASI) profile to derive new 3D shear velocity models for the crust. Continuous records from 2014 and 2015 are cross-correlated to estimate Green's functions of Rayleigh and Love waves propagating between the station pairs. Group velocities extracted from the cross-correlations are inverted to obtain isotropic 3D Rayleigh- and Love-wave shear-wave velocity models. Our models image several velocity anomalies and contrasts and reveal details of the crustal structure. Velocity variations at short periods correlate very closely with the lithologies of tectonic units at the surface and projected to depth. Low-velocity zones, associated with the Po and Molasse sedimentary basins, are imaged well to the south and north of the Alps, respectively. We find large high-velocity zones associated with the crystalline basement that forms the core of the Tauern Window. Small-scale velocity anomalies are also aligned with geological units of the Austroalpine nappes. Clear velocity contrasts in the Tauern Window along vertical cross sections of the velocity model show the depth extent of the tectonic units and their bounding faults. A mid-crustal velocity contrast is interpreted as a manifestation of intracrustal decoupling in the Eastern Alps that accommodated eastward escape of the Alcapa block.

Стилі APA, Harvard, Vancouver, ISO та ін.

22

Maradudin, A. A., I. Simonsen, J. Polanco, and R. M. Fitzgerald. "Rayleigh and Wood anomalies in the diffraction of light from a perfectly conducting reflection grating." Journal of Optics 18, no. 2 (January 6, 2016): 024004. http://dx.doi.org/10.1088/2040-8978/18/2/024004.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

23

Vecsey, Luke, Cathy Hier, Dave Yuen, and Erik Sevre. "Two Dimensional Wavelet Analysis Applied to Geoid Anomalies Mixing and High Rayleigh Number Mantle Convection." Visual Geosciences 6, no. 3 (November 2001): 1–6. http://dx.doi.org/10.1007/s10069-001-1016-1.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

24

Aprillo, Laksamana Agung, Hendy Santosa, and Faisal Hadi. "Analisis Total Electron Content (TEC) Menggunakan Continous Wavelet Transform Sebagai Indikator Prekursor Gempa Bumi Di Wilayah Provinsi Bengkulu." JURNAL AMPLIFIER : JURNAL ILMIAH BIDANG TEKNIK ELEKTRO DAN KOMPUTER 9, no. 2 (November 30, 2019): 27–33. http://dx.doi.org/10.33369/jamplifier.v9i2.15380.

Повний текст джерела

Анотація:

ABSTRACT Bengkulu is one of 34 provinces in Indonesia which is a megathrust region. So Bengkulu province is often hit by many large earthquakes with shallow depth. TEC anomaly was analyzed based on three electromagnetic waves radiated by an earthquake. The total electron content (TEC) anomaly is seen through the global positioning system (GPS) dual-frequency radio signal data. The continuous wavelet transform (CWT) method is used to divide the signal analysis into several sections according to the electromagnetic wave frequency range of acoustic (2.5 mHz) -3 mHz), gravity waves (1 mHz-2.8 mHz) and rayleigh waves (5 mHz-33 mHz). GPS observation data for 9 days is calculated using the Standard deviation (2?) method to see trends in data changes. The analysis shows anomalies in the September 12 2007 earthquake (7.9 Mw), the March 5 2010 earthquake (6.3 Mw) and the August 4 2011 earthquake (6.0 Mw). Anomalies are detected 1 to 5 hours before an earthquake occurs. TEC anomalies that occur may be related to the process of preseismic before the earthquake and may be an early sign of an earthquake.Keyword: earthquake, total electron content, continous wavelet transform, standard deviation

Стилі APA, Harvard, Vancouver, ISO та ін.

25

Xu, Xiaoming, Dazhou Zhang, Xiang Huang, and Xiaoman Cao. "Deformation of the Crust and Upper Mantle beneath the North China Craton and Its Adjacent Areas Constrained by Rayleigh Wave Phase Velocity and Azimuthal Anisotropy." Remote Sensing 14, no. 1 (December 28, 2021): 110. http://dx.doi.org/10.3390/rs14010110.

Повний текст джерела

Анотація:

The North China Craton (NCC) has experienced strong tectonic deformation and lithospheric thinning since the Cenozoic. To better constrain the geodynamic processes and mechanisms of the lithospheric deformation, we used a linear damped least squares method to invert simultaneously Rayleigh wave phase velocity and azimuthal anisotropy at periods of 10–80 s with teleseismic data recorded by 388 permanent stations in the NCC and its adjacent areas. The results reveal that the anomalies of Rayleigh wave phase velocity and azimuthal anisotropy are in good agreement with the tectonic domains in the study area. Low-phase velocities appear in the rift grabens and sedimentary basins at short periods. A rotation pattern of the fast axis direction of the Rayleigh wave together with a distinct low-velocity anomaly occurs around the Datong volcano. A NW–SE trending azimuthal anisotropy and a low-velocity anomaly at periods of 60–80 s are observed subparallel to the Zhangbo fault zone. The whole lithosphere domain of the Ordos block shows a high-phase velocity and counterclockwise rotated fast axis. The northeastern margin of the Tibetan plateau is dominated by a low-velocity and coherent NW–SE fast axis direction. We infer that the subduction of the Paleo-Pacific plate and eastward material escape of the Tibetan plateau mainly contribute to the deformation of the crust and upper mantle in the NCC.

Стилі APA, Harvard, Vancouver, ISO та ін.

26

Wang, F., A. Lakhtakia, and R. Messier. "Coupling of Rayleigh-Wood anomalies and the circular Bragg phenomenon in slanted chiral sculptured thin films." European Physical Journal Applied Physics 20, no. 2 (October 25, 2002): 91–103. http://dx.doi.org/10.1051/epjap:2002079.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

27

Wang, F., A. Lakhtakia, and R. Messier. "Coupling of Rayleigh-Wood anomalies and the circular Bragg phenomenon in slanted chiral sculptured thin films." European Physical Journal Applied Physics 24, no. 1 (September 29, 2003): 91. http://dx.doi.org/10.1051/epjap:2003069.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

28

Zhang, Shanwen, and Heshig Bayan. "Using the compensating effect for Rayleigh anomalies to design a type of broadband mid-IR grating." Optics Express 16, no. 10 (May 1, 2008): 7049. http://dx.doi.org/10.1364/oe.16.007049.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

29

Gromyko, D. A., S. A. Dyakov, V. A. Zinovyev, S. G. Tikhodeev, and N. A. Gippius. "Resonant mode approximation of the scattering matrix of photonic crystal slabs near several Wood-Rayleigh anomalies." Photonics and Nanostructures - Fundamentals and Applications 50 (July 2022): 101015. http://dx.doi.org/10.1016/j.photonics.2022.101015.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

30

Xiao, Xiao, Shihua Cheng, Jianping Wu, Weilai Wang, Li Sun, Xiaoxin Wang, and Lianxing Wen. "Shallow seismic structure beneath the continental China revealed by P-wave polarization, Rayleigh wave ellipticity and receiver function." Geophysical Journal International 225, no. 2 (January 20, 2021): 998–1019. http://dx.doi.org/10.1093/gji/ggab022.

Повний текст джерела

Анотація:

SUMMARY We construct a high-resolution shallow 3-D seismic model in the top 10 km of the upper crust in the continental China, with constraints of P polarization, Rayleigh wave ellipticity and receiver function obtained from records of 3848 seismic stations. Our 3-D seismic model has a spatial resolution of 0.6–1.2° in the north–south seismic belt and the trans-north China orogen, and 1–2° in the rest of the continental China (except the Tarim basin and the southwest Tibet). The seismic model exhibits low velocity anomalies of deposits in major sedimentary basins and high velocity anomalies of crustal bedrocks in young orogenic belts and old tectonic blocks. The inferred sediment thickness maps display thick deposits in major sedimentary basins, some compacted sediments in the intermontane basins in young orogenic belts and little sediments in old tectonic blocks. We also discuss compaction effects of the sediments and implications of tectonic history and geological evolution of the major basins in the continental China based on the inferred seismic models. This study provides an effective mean of seismic imaging through joint inversion of various seismic constraints and establishes a framework of seismic data sharing for future studies in the seismological community in a first step of developing a China Seismological Reference Model.

Стилі APA, Harvard, Vancouver, ISO та ін.

31

Mound, Jon E., and Christopher J. Davies. "Heat transfer in rapidly rotating convection with heterogeneous thermal boundary conditions." Journal of Fluid Mechanics 828 (September 5, 2017): 601–29. http://dx.doi.org/10.1017/jfm.2017.539.

Повний текст джерела

Анотація:

Convection in the metallic cores of terrestrial planets is likely to be subjected to lateral variations in heat flux through the outer boundary imposed by creeping flow in the overlying silicate mantles. Boundary anomalies can significantly influence global diagnostics of core convection when the Rayleigh number, $Ra$, is weakly supercritical; however, little is known about the strongly supercritical regime appropriate for planets. We perform numerical simulations of rapidly rotating convection in a spherical shell geometry and impose two patterns of boundary heat flow heterogeneity: a hemispherical $Y_{1}^{1}$ spherical harmonic pattern; and one derived from seismic tomography of the Earth’s lower mantle. We consider Ekman numbers $10^{-4}\leqslant E\leqslant 10^{-6}$, flux-based Rayleigh numbers up to ${\sim}800$ times critical, and a Prandtl number of unity. The amplitude of the lateral variation in heat flux is characterised by $q_{L}^{\ast }=0$, 2.3, 5.0, the peak-to-peak amplitude of the outer boundary heat flux divided by its mean. We find that the Nusselt number, $Nu$, can be increased by up to ${\sim}25\,\%$ relative to the equivalent homogeneous case due to boundary-induced correlations between the radial velocity and temperature anomalies near the top of the shell. The $Nu$ enhancement tends to become greater as the amplitude and length scale of the boundary heterogeneity are increased and as the system becomes more supercritical. This $Ra$ dependence can steepen the $Nu\propto Ra^{\unicode[STIX]{x1D6FE}}$ scaling in the rotationally dominated regime, with $\unicode[STIX]{x1D6FE}$ for our most extreme case approximately 20 % greater than the equivalent homogeneous scaling. Therefore, it may be important to consider boundary heterogeneity when extrapolating numerical results to planetary conditions.

Стилі APA, Harvard, Vancouver, ISO та ін.

32

Bruno, Oscar P., and Agustin G. Fernandez-Lado. "On the evaluation of quasi-periodic Green functions and wave-scattering at and around Rayleigh-Wood anomalies." Journal of Computational Physics 410 (June 2020): 109352. http://dx.doi.org/10.1016/j.jcp.2020.109352.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

33

Rasskazov, Ilia L., Nishikant Sonwalkar, and P. Scott Carney. "Light scattering by plasmonic disks and holes arrays: different or the same?" Journal of Physics D: Applied Physics 55, no. 45 (September 19, 2022): 455104. http://dx.doi.org/10.1088/1361-6463/ac8ffc.

Повний текст джерела

Анотація:

Abstract We suggest a strategy for designing regular 2D arrays of nanoholes (NHs) in metal films with far-field scattering properties similar to that of regular 2D arrays of nanodisks (NDs) with the same periodicity. Full-wave simulations for perfectly conducting, Ag and Au NDs and respectively designed arrays of NHs demonstrate a minor difference between far-field properties either at wavelengths corresponding to Wood–Rayleigh anomalies of the arrays or in a broad wavelength range, depending on the array periodicity and sizes of NDs (NHs). Our results have broad implications in plasmon-enhanced-driven applications, including optoelectronic and photovoltaic devices, where the NH arrays are preferable to be fabricated for nano-structured optics.

Стилі APA, Harvard, Vancouver, ISO та ін.

34

Bruno, Oscar P., Stephen P. Shipman, Catalin Turc, and Venakides Stephanos. "Three-dimensional quasi-periodic shifted Green function throughout the spectrum, including Wood anomalies." Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 473, no. 2207 (November 2017): 20170242. http://dx.doi.org/10.1098/rspa.2017.0242.

Повний текст джерела

Анотація:

This work, part II in a series, presents an efficient method for evaluation of wave scattering by doubly periodic diffraction gratings at or near what are commonly called ‘Wood anomaly frequencies’. At these frequencies, there is a grazing Rayleigh wave, and the quasi-periodic Green function ceases to exist. We present a modification of the Green function by adding two types of terms to its lattice sum. The first type are transversely shifted Green functions with coefficients that annihilate the growth in the original lattice sum and yield algebraic convergence. The second type are quasi-periodic plane wave solutions of the Helmholtz equation which reinstate certain necessary grazing modes without leading to blow-up at Wood anomalies. Using the new quasi-periodic Green function, we establish, for the first time, that the Dirichlet problem of scattering by a smooth doubly periodic scattering surface at a Wood frequency is uniquely solvable. We also present an efficient high-order numerical method based on this new Green function for scattering by doubly periodic surfaces at and around Wood frequencies. We believe this is the first solver able to handle Wood frequencies for doubly periodic scattering problems in three dimensions. We demonstrate the method by applying it to acoustic scattering.

Стилі APA, Harvard, Vancouver, ISO та ін.

35

Liu, Yuhan, and Shuanggen Jin. "Ionospheric Rayleigh Wave Disturbances Following the 2018 Alaska Earthquake from GPS Observations." Remote Sensing 11, no. 8 (April 13, 2019): 901. http://dx.doi.org/10.3390/rs11080901.

Повний текст джерела

Анотація:

Big earthquakes often excite the acoustic resonance between the earth’s surface and the lower atmosphere. The perturbations can propagate upward into the ionosphere and trigger ionospheric anomalies detected by dual-frequency GPS observations, but coseismic ionospheric disturbance (CID) directivity and mechanism are not clear. In this paper, the ionospheric response to the Mw = 7.9 Alaska earthquake on 23 January 2018 is investigated from about 100 continuous GPS stations near the epicenter. The fourth-order zero-phase Butterworth band-pass filter with cutoffs of 2.2 mHz and 8 mHz is applied to obtain the ionospheric disturbances. Results show that the CIDs with an amplitude of up to 0.06 total electron content units (TECU) are detected about 10 min after the Alaska earthquake. The CIDs are as a result of the upward propagation acoustic waves triggered by the Rayleigh wave. The propagation velocities of TEC disturbances are around 2.6 km/s, which agree well with the wave propagation speed of 2.7 km/s detected by the bottom pressure records. Furthermore, the ionospheric disturbances following the 2018 Mw = 7.9 Alaska earthquake are inhomogeneous and directional which is rarely discussed. The magnitude of ionospheric disturbances in the western part of the epicenter is more obvious than in the eastern part. This phenomenon also corresponds to the data obtained from the seismographs and bottom pressure records (BPRs) at the eastern and western side of the epicenter.

Стилі APA, Harvard, Vancouver, ISO та ін.

36

Weidner, Erik, Caroline Beghein, Quancheng Huang, and Nicholas Schmerr. "Upper mantle radial anisotropy under the Indian Ocean from higher mode surface waves and a hierarchical transdismensional approach." Geophysical Journal International 228, no. 1 (August 20, 2021): 78–101. http://dx.doi.org/10.1093/gji/ggab340.

Повний текст джерела

Анотація:

SUMMARY We investigated the likelihood of radial anisotropy in the shallow and deep upper mantle, including the mantle transition zone (MTZ) under the Indian Ocean. Seismic anisotropy can be an indicator of mantle deformation through lattice preferred orientation of anisotropic crystals in the mantle. It has thus the potential to illuminate Earth’s dynamic interior, but previous seismic tomography studies have not achieved consensus on the existence of radial anisotropy below ∼250 km depth. We developed a fully nonlinear transdimensional hierarchical Bayesian Markov Chain Monte Carlo approach to invert fundamental and higher mode surface wave dispersion data and applied it to a subset of a global Love and Rayleigh wave data set. We obtained posterior model parameter distributions for shear wave velocity (VS) and radial anisotropy ξ under the Indian Ocean. These posterior model distributions were used to calculate the probability of having radial anisotropy at different depths. We demonstrated that separate inversions of Love and Rayleigh waves yield models compatible with the results of joint inversions within uncertainties. The obtained pattern of VS anomalies agrees with most previous studies. They display negative anomalies along ridges in the uppermost mantle, but those are stronger than for regularized inversions. The Central Indian Ridge and the Southeastern Indian Ridge present velocity anomalies that extend to ∼200 km depth, whereas the Southwestern Indian Ridge seems to have a shallower origin. Weaker, laterally variable velocity perturbations were found at larger depths. The anisotropy models differ more strongly from regularized inversion results and their uncertainties were rather large. We found that anisotropy models from regularized inversions also depend on the chosen parametrization, which is consistent with the existence of a large model null-space. Apart from a fast horizontally polarized shear wave signal in the top 100 km, likely reflecting the horizontal plate motion due to asthenospheric deformation, no clear relation to surface geology was detected in the anisotropy models. We found that, although the anisotropy model uncertainties are rather large, and lateral variations are present, the data generally prefer at least 1 per cent anisotropy in the MTZ with fast vertically polarized shear waves, within errors. Incorporating group velocity data did not help better constrain deep structure by reducing parameter trade-offs. We also tested the effect of prior constraints on the 410- and 660-km topography and found that the undulations of these discontinuities had little effect on the resulting models in our study region.

Стилі APA, Harvard, Vancouver, ISO та ін.

37

Salmon, Olivia E., Lisa R. Welp, Michael E. Baldwin, Kristian D. Hajny, Brian H. Stirm, and Paul B. Shepson. "Vertical profile observations of water vapor deuterium excess in the lower troposphere." Atmospheric Chemistry and Physics 19, no. 17 (September 12, 2019): 11525–43. http://dx.doi.org/10.5194/acp-19-11525-2019.

Повний текст джерела

Анотація:

Abstract. We use airborne measurements of water vapor (H2Ov) stable isotopologues and complementary meteorological observations to examine how boundary layer (BL) dynamics, cloud processing, and atmospheric mixing influence the vertical structure of δD, δ18O, and deuterium excess (d excess =δD–8×δ18O) in the BL, inversion layer (INV), and lower free troposphere (FT). Flights were conducted around two continental US cities in February–March 2016 and included vertical profiles extending from near the surface to ≤2 km. We examine observations from three unique case study flights in detail. One case study shows observations that are consistent with Rayleigh isotopic distillation theory coinciding with clear skies, dry adiabatic lapse rates within the boundary layer, and relatively constant vertical profiles of wind speed and wind direction. This suggests that the air mass retained the isotopic fingerprint of dehydration during moist adiabatic processes upwind of the study area. Also, observed d-excess values in the free troposphere were sometimes larger than Rayleigh theory predicts, which may indicate mixing of extremely dehydrated air from higher altitudes. The two remaining case studies show isotopic anomalies in the d-excess signature relative to Rayleigh theory and indicate cloud processes and complex boundary layer development. The most notable case study with stratocumulus clouds present had extremely low (negative) d-excess values at the interface of the inversion layer and the free troposphere, which is possibly indicative of cloud or rain droplet evaporation. We discuss how in situ H2Ov stable isotope measurements, and d excess in particular, could be useful for improving our understanding of water phase changes, transport, and mixing that occurs between the BL, INV, and FT.

Стилі APA, Harvard, Vancouver, ISO та ін.

38

Muhumuza, K. "A Feasibility Study on Monitoring Crustal Structure Variations by Direct Comparison of Surface Wave Dispersion Curves from Ambient Seismic Noise." International Journal of Geophysics 2020 (February 3, 2020): 1–11. http://dx.doi.org/10.1155/2020/5269537.

Повний текст джерела

Анотація:

This work assesses the feasibility of the direct use of surface-wave dispersion curves from seismic ambient noise to gain insight into the crustal structure of Bransfield Strait and detect seasonal seismic velocity changes. We cross-correlated four years of vertical component ambient noise data recorded by a seismic array in West Antarctica. To estimate fundamental mode Rayleigh wave Green’s functions, the correlations are computed in 4-hr segments, stacked over 1-year time windows and moving windows of 3 months. Rayleigh wave group dispersion curves are then measured on two spectral bands—primary (10–30 s) and secondary (5–10 s) microseisms—using frequency-time analysis. We analyze the temporal evolution of seismic velocity by comparing dispersion curves for the successive annual and 3-month correlation stacks. Our main assumption was that the Green’s functions from the cross-correlations, and thus the dispersion curves, remain invariant if the crustal structure remains unchanged. Maximum amplitudes of secondary microseisms were observed during local winter when the Southern Ocean experiences winter storms. The Rayleigh wave group velocity ranges between 2.1 and 3.7 km/s, considering our period range studied. Interannual velocity variations are not much evident. We observe a slight velocity decrease in summer and increase in winter, which could be attributed to the pressure melting of ice and an increase in ice mass, respectively. The velocity anomalies observed within the crust and upper mantle structure correlate with the major crustal and upper mantle features known from previous studies in the area. Our results demonstrate that the direct comparison of surface wave dispersion curves extracted from ambient noise might be a useful tool in monitoring crustal structure variations.

Стилі APA, Harvard, Vancouver, ISO та ін.

39

Utyushev, Anton D., Vadim I. Zakomirnyi, Alexander E. Ershov, Valeriy S. Gerasimov, Sergey V. Karpov, and Ilia L. Rasskazov. "Collective Lattice Resonances in All-Dielectric Nanostructures under Oblique Incidence." Photonics 7, no. 2 (March 28, 2020): 24. http://dx.doi.org/10.3390/photonics7020024.

Повний текст джерела

Анотація:

Collective lattice resonances (CLRs) emerging under oblique incidence in 2D finite-size arrays of Si nanospheres have been studied with the coupled dipole model. We show that hybridization between the Mie resonances localized on a single nanoparticle and angle-dependent grating Wood–Rayleigh anomalies allows for the efficient tuning of CLRs across the visible spectrum. Complex nature of CLRs in arrays of dielectric particles with both electric dipole (ED) and magnetic dipole (MD) resonances paves a way for a selective and flexible tuning of either ED or MD CLR by an appropriate variation of the angle of incidence. The importance of the finite-size effects, which are especially pronounced for CLRs emerging for high diffraction orders under an oblique incidence has been also discussed.

Стилі APA, Harvard, Vancouver, ISO та ін.

40

Spoor, P. S., and J. D. Maynard. "Numerical anomalies in the Rayleigh–Ritz method for calculating the normal mode vibrations of arbitrarily shaped elastic solids." Journal of the Acoustical Society of America 97, no. 5 (May 1995): 3326. http://dx.doi.org/10.1121/1.412811.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

41

Park, Jae Woung, Kwang Hee Im, David K. Hsu, Uk Heo, K. S. Lee, Y. H. Kim, Sun Kyu Kim, and In Young Yang. "On Feasibility of Ply-Layup Orientation in CF/Epoxy Composite Laminates Using Rayleigh Probes." Advanced Materials Research 29-30 (November 2007): 299–302. http://dx.doi.org/10.4028/www.scientific.net/amr.29-30.299.

Повний текст джерела

Анотація:

A nondestructive technique would be very beneficial, which could be used to test the CF/Epoxy composite laminates. A new method for nondestructively determining the ply layup in a composite laminate is presented. A one-sided pitch-catch setup was used in the detection and evaluation of flaws and material anomalies in the composite laminates. Two Rayleigh wave transducers were joined head-to-head and used in the pitch-catch mode on the surface of the composites. The pitch-catch signal was found to be more sensitive than normal incidence backwall echo of longitudinal wave to subtle flaw conditions in the composite. Also the other method employs a normal-incidence longitudinal ultrasound to perform C-scan of ply interfaces of the laminate, and extracts fiber orientation information from the ultrasonic reflection in the laminate. Using two-dimensional spatial Fourier transform, interface C-scan images were transformed into quantitatively angular distribution plots to show the fiber orientation information therein and to determine the orientation of the ply. Therefore, it is found that the efficiency of developed system shows between the one-sided pitch-catch testing and C-scan images in characterizing ply-layup orientation of the laminates.

Стилі APA, Harvard, Vancouver, ISO та ін.

42

PARK, JE-WOONG, IN-YOUNG YANG, KIL-SUNG LEE, DAVID K. HSU, YOUNG-TAE CHO, SUNG-JIN SONG, and KWANG-HEE IM. "ONE-SIDED ULTRASONIC CHARACTERIZATION OF CFRP COMPOSITE LAMINATES." Modern Physics Letters B 22, no. 11 (May 10, 2008): 815–19. http://dx.doi.org/10.1142/s0217984908015437.

Повний текст джерела

Анотація:

Ultrasonic NDE of composite laminates is usually analyzed on the backwall echoes of the specimen. In the inspection of actual composite structures, the back surface of the part was curved or contained complex geometry and did not provide a usable backwall echo. In this work, a one-sided pitch-catch setup was used in the detection and evaluation of flaws and material anomalies in solid composite laminates. Two miniature potted Rayleigh wave transducers (for generating surface waves in contact mode on steel) were joined head-to-head and used in the pitch-catch mode on the surface of composites. The pitch-catch signal was found to be more sensitive than normal incidence backwall echo of longitudinal wave to fiber orientation of the CFRP composites, including low level porosity, ply waviness, and cracks.

Стилі APA, Harvard, Vancouver, ISO та ін.

43

Hwang, Taek-Yong, Yong-dae Kim, Jongweon Cho, Hai-Joong Lee, Hyo-Soo Lee, and Byounghwak Lee. "Multi-Angular Colorimetric Responses of Uni- and Omni-Directional Femtosecond Laser-Induced Periodic Surface Structures on Metals." Nanomaterials 11, no. 8 (August 5, 2021): 2010. http://dx.doi.org/10.3390/nano11082010.

Повний текст джерела

Анотація:

We investigated the colorimetric behaviors of metal surfaces with unidirectional low-spatial-frequency laser-induced periodic surface structures (UD-LSFLs) and omnidirectional LSFLs (OD-LSFLs) fabricated using femtosecond laser pulse irradiation. With the CIE standard illuminant D65, incident at −45°, we show that UD-LSFLs on metals transform polished metals to gonio-apparent materials with a unique behavior of colorimetric responses, depending on both the detection and rotation angles, whereas OD-LSFLs have nearly uniform gonio-apparent colors at each detection angle, regardless of their rotation. These colorimetric behaviors can be observed not only at the angles of diffraction but also near the angle of reflection, and we find that the power redistribution due to Rayleigh anomalies also plays an important role in the colorimetric responses of UD- and OD-LSFLs, in addition to diffraction.

Стилі APA, Harvard, Vancouver, ISO та ін.

44

Clouser, Robert H., and Charles A. Langston. "Modeling P-Rg conversions from isolated topographic features near the NORESS array." Bulletin of the Seismological Society of America 85, no. 3 (June 1, 1995): 859–73. http://dx.doi.org/10.1785/bssa0850030859.

Повний текст джерела

Анотація:

Abstract Using the T-matrix, or extended boundary condition, method, we model seismic-wave scattering from earth models with one-dimensional (1D) isolated topographic features. The earth model is simple, but we are primarily interested in free surface interactions. Scattering phenomena encountered in this model would presumably also operate in more realistic two-dimensional (2D) models. This study is motivated by observations suggesting that surface topography generates coda waves, which are relatively large-amplitude arrivals following major seismic phases. For sinusoidal periodic surfaces, large-amplitude anomalies in the surface displacement spectrum correspond to P-to-Rayleigh (P-Rg), S-to-Rayleigh (S-Rg), and other mode conversions. For isolated topographic features, these conversions still exist. We modeled teleseismic P-Rg conversions from isolated hills in order to understand and confirm the origin of observed conversions near the NORESS array. Parameter studies indicate that P-Rg and critical P-P conversion amplitudes increase roughly-linearly with scatterer relief, but are insensitive to changes in teleseismic ray parameter. Forward-scattered Rg waves are always two to three times larger than backscattered Rg waves. Poor fits to the observed P-Rg amplitudes (relative to the incident P waves) suggest that more realistic and complicated structure effects must be included. For example, it is well known that P-wave amplitudes vary considerably across the NORSAR array due to subsurface structures.

Стилі APA, Harvard, Vancouver, ISO та ін.

45

Ratilal, Purnima, Tianrun Chen, and Nicholas C. Makris. "Analytic mean and variance of forward propagated field through random internal waves and subbottom anomalies with Rayleigh–Born scattering." Journal of the Acoustical Society of America 115, no. 5 (May 2004): 2549–50. http://dx.doi.org/10.1121/1.4783755.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

46

Maradudin, A. A., and I. Simonsen. "Rayleigh and Wood anomalies in the diffraction of acoustic waves from the periodically corrugated surface of an elastic medium." Low Temperature Physics 42, no. 5 (May 2016): 354–60. http://dx.doi.org/10.1063/1.4948617.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

47

Davies, Christopher J., and Jon E. Mound. "Mantle-induced temperature anomalies do not reach the inner core boundary." Geophysical Journal International 219, Supplement_1 (June 10, 2019): S21—S32. http://dx.doi.org/10.1093/gji/ggz254.

Повний текст джерела

Анотація:

SUMMARY Temperature anomalies in Earth’s liquid core reflect the vigour of convection and the nature and extent of thermal core–mantle coupling. Numerical simulations suggest that longitudinal temperature anomalies forced by lateral heat flow variations at the core–mantle boundary (CMB) can greatly exceed the anomalies that arise in homogeneous convection (i.e. with no boundary forcing) and may even penetrate all the way to the inner core boundary. However, it is not clear whether these simulations access the relevant regime for convection in Earth’s core, which is characterized by rapid rotation (low Ekman number E) and strong driving (high Rayleigh number Ra). We access this regime using numerical simulations of non-magnetic rotating convection with imposed heat flow variations at the outer boundary (OB) and investigate the amplitude and spatial pattern of thermal anomalies, focusing on the inner and outer boundaries. The 108 simulations cover the parameter range 10−4 ≤ E ≤ 10−6 and Ra = 1−800 times the critical value. At each Ra and E we consider two heat flow patterns—one derived from seismic tomography and the hemispheric $Y_1^1$ spherical harmonic pattern—with amplitudes measured by the parameter q⋆ = 2.3, 5 as well as the case of homogeneous convection. At the OB the forcing produces strong longitudinal temperature variations that peak in the equatorial region. Scaling relations suggest that the longitudinal variations are weakly dependent on E and Ra and are much stronger than in homogeneous convection, reaching O(1) K at core conditions if q⋆ ≈ 35. At the inner boundary, latitudinal and longitudinal temperature variations depend weakly on Ra and q⋆ and decrease strongly with E, becoming practically indistinguishable between homogeneous and heterogeneous cases at E = 10−6. Interpreted at core conditions our results suggest that heat flow variations on the CMB are unlikely to explain the large-scale variations observed by seismology at the top of the inner core.

Стилі APA, Harvard, Vancouver, ISO та ін.

48

Rezeau, Hervé, Robert Moritz, Jörn-Frederik Wotzlaw, Samvel Hovakimyan, and Rodrik Tayan. "Zircon Petrochronology of the Meghri-Ordubad Pluton, Lesser Caucasus: Fingerprinting Igneous Processes and Implications for the Exploration of Porphyry Cu-Mo Deposits." Economic Geology 114, no. 7 (November 1, 2019): 1365–88. http://dx.doi.org/10.5382/econgeo.4671.

Повний текст джерела

Анотація:

Abstract The trace element composition of zircon, especially in tandem with U-Pb geochronology, has become a powerful tool for tracing magmatic processes associated with the formation of porphyry copper deposits. However, the use of the redox-sensitive Eu and Ce anomalies as a potential mineral exploration proxy is controversial. This study presents a comprehensive, temporally constrained data set of zircon trace element compositions (n = 645) for three compositionally distinct magmatic series identified in the Meghri-Ordubad pluton, southernmost Lesser Caucasus. The 30 million years of Cenozoic magmatism in the Meghri-Ordubad pluton are associated with several ore-forming pulses leading to the formation of porphyry copper deposits and epithermal-style mineralization. Our zircon geochemical data constrain the thermal and chemical evolution of this complex intrusive suite and allow an evaluation of the usefulness of zircon as a mineral exploration proxy for porphyry copper deposits. Our results combined with Rayleigh fractionation modeling indicate that the trace element composition of zircon (Th/U, Hf, Ti, YbN/DyN, Eu anomalies) is influenced by the composition and the water concentration of the parental magma, as well as by co-crystallizing titanite and apatite. In contrast, the variations of Ce anomalies remain difficult to explain by magmatic processes and could rather be ascribed to relative fluctuations of the redox conditions. In the Meghri-Ordubad pluton, we do not observe any systematic patterns between the trace element composition in zircons and the different ore-forming pulses. This questions the reliability of using the trace element composition in zircon as an exploration mineral proxy, and it rather emphasizes that a good knowledge of the entire magmatic evolution of a metallogenic province is required.

Стилі APA, Harvard, Vancouver, ISO та ін.

49

Chen, Zhongen, Xuewei Bao, and Wencai Yang. "Shallow Shear-Wave Velocity Structure beneath the West Lake Area in Hangzhou, China, from Ambient-Noise Tomography." Remote Sensing 13, no. 14 (July 20, 2021): 2845. http://dx.doi.org/10.3390/rs13142845.

Повний текст джерела

Анотація:

Urban geophysical exploration plays an important role in the sustainable development of and the mitigation of geological hazards in metropolitan areas. However, it is not suitable to implement active seismic methods in densely populated urban areas. The rapidly developing ambient-noise tomography (ANT) method is a promising technique for imaging the near-surface seismic velocity structure. We selected the West Lake area of the city of Hangzhou as a case study to probe the shallow subsurface shear-wave velocity (Vs) structure using ANT. We conducted seismic interferometry on the ambient-noise data recorded by 28 seismograph stations during a time period of 17 days. Fundamental-mode Rayleigh-wave group- and phase-velocity dispersion data were measured from cross-correlation functions and then inverted for a 3D Vs model of the uppermost 1 km that covers an area of about 7 km × 8 km. The tomographic results reveal two prominent anomalies, with high velocities in the southwest and low velocities in the northeast. The fast anomaly corresponds to the presence of limestone and sandstone, whereas the slow anomaly is due to the relatively low-velocity rhyolite and volcanic tuff in the area. The boundary between the two anomalies lies to the NE of an NW–SE trending fault, indicating that the fault dips toward the NE. In addition, the pronounced low-velocity anomalies appear under the Baoshi mountain, likely due to the thick rhyolite and volcanic tuff beneath the extinct volcano. Our results correlate well with regional geological features and suggest that ANT could be a promising technique for facilitating the exploration of urban underground space.

Стилі APA, Harvard, Vancouver, ISO та ін.

50

Levshin, Anatoli, Ludmila Ratnikova, and Jon Berger. "Peculiarities of surface-wave propagation across central Eurasia." Bulletin of the Seismological Society of America 82, no. 6 (December 1, 1992): 2464–93. http://dx.doi.org/10.1785/bssa0820062464.

Повний текст джерела

Анотація:

Abstract The recent installation of six broadband digital IRIS/IDA seismic stations in the USSR has provided new opportunities for studying surface-wave propagation across Eurasia. Group velocities of fundamental Rayleigh and Love modes between epicenters and these stations were determined for 35 events that occurred since April 1989 to the middle of July 1990 near Eurasia. Differential phase velocities were found for the same arrivals along paths between several pairs of stations. Group and phase velocities were obtained in the period range from 15 to 300 sec. Frequency-time polarization analysis was used for studying polarization properties of surface waves. In some cases, significant anomalies in the particle motion for periods up to 100 sec were observed. They are attributed to surface-wave refraction and scattering due to lateral inhomogeneities at the boundaries and inside the Eurasia continent.

Стилі APA, Harvard, Vancouver, ISO та ін.

Статті в журналах з теми "Rayleigh anomalies"

Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями