Towards Structural Imaging using Seismic Ambient Field Correlation Artifacts

Geophysical Journal International ◽

10.1093/gji/ggab038 ◽

2021 ◽

Author(s):

Lise Retailleau ◽

Gregory C Beroza

Keyword(s):

Wave Propagation ◽

Correlation Functions ◽

Structural Imaging ◽

Structural Variations ◽

Array Analysis ◽

Seismic Stations ◽

Central California ◽

Field Correlation ◽

The Waves ◽

Great Valley

Summary Correlations of the ambient seismic field recorded by seismic stations carry information about the wave propagation between the stations. They also contain information about the ambient field - both the source of the ambient field, and sources of scattering that contribute to it. The waves that comprise the ambient field are subject to scattering due to the heterogeneous Earth, which can generate supplementary arrivals on the correlation functions. We use these effects to locate sources of signals linked to scattering. For this analysis, we use correlation functions computed from continuous signals recorded between 2013 and 2015 by a line of seismic stations in Central California. We identify spurious arrivals on the Vertical to Vertical and Transverse to Transverse correlation functions and use array analysis to map the source of scattering, which is linked to strong structural variations in the Coast ranges and at the border of the Great Valley.

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Innovative Seismic Array Analysis for Studies of Wave Propagation in the Earth

10.21236/ada376283 ◽

1999 ◽

Author(s):

Gary L. Pavlis

Keyword(s):

Wave Propagation ◽

Seismic Array ◽

Array Analysis ◽

The Earth

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Anomalous Anderson localization behavior in gain-loss balanced non-Hermitian systems

Nanophotonics ◽

10.1515/nanoph-2020-0306 ◽

2020 ◽

Vol 10 (1) ◽

pp. 443-452

Author(s):

Tianshu Jiang ◽

Anan Fang ◽

Zhao-Qing Zhang ◽

Che Ting Chan

Keyword(s):

Wave Propagation ◽

Electromagnetic Waves ◽

Anderson Localization ◽

Random Media ◽

Normal Incidence ◽

Disordered Media ◽

One Dimensional ◽

Gain Loss ◽

The Waves ◽

Localization Behavior

AbstractIt has been shown recently that the backscattering of wave propagation in one-dimensional disordered media can be entirely suppressed for normal incidence by adding sample-specific gain and loss components to the medium. Here, we study the Anderson localization behaviors of electromagnetic waves in such gain-loss balanced random non-Hermitian systems when the waves are obliquely incident on the random media. We also study the case of normal incidence when the sample-specific gain-loss profile is slightly altered so that the Anderson localization occurs. Our results show that the Anderson localization in the non-Hermitian system behaves differently from random Hermitian systems in which the backscattering is suppressed.

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Airglow Measurements of Gravity Wave Propagation and Damping over Kolhapur (16.5°N, 74.2°E)

International Journal of Geophysics ◽

10.1155/2014/514937 ◽

2014 ◽

Vol 2014 ◽

pp. 1-9 ◽

Cited By ~ 6

Author(s):

R. N. Ghodpage ◽

A. Taori ◽

P. T. Patil ◽

S. Gurubaran ◽

A. K. Sharma ◽

...

Keyword(s):

Wave Propagation ◽

Gravity Wave ◽

Meridional Wind ◽

Vertical Wavelength ◽

Emission Layer ◽

Positive Correlation ◽

Intensity Measurements ◽

Wind Shears ◽

The Waves ◽

Airglow Intensity

Simultaneous mesospheric OH and O (1S) night airglow intensity measurements from Kolhapur (16.8°N, 74.2°E) reveal unambiguous gravity wave signatures with periods varying from 01 hr to 9 hr with upward propagation. The amplitudes growth of these waves is found to vary from 0.4 to 2.2 while propagating from the OH layer (~87 km) to the O (1S) layer (~97 km). We find that vertical wavelength of the observed waves increases with the wave period. The damping factors calculated for the observed waves show large variations and that most of these waves were damped while traveling from the OH emission layer to the O (1S) emission layer. The damping factors for the waves show a positive correlation at vertical wavelengths shorter than 40 km, while a negative correlation at higher vertical wavelengths. We note that the damping factors have stronger positive correlation with meridional wind shears compared to the zonal wind shears.

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Near earthquakes in Central California*

Bulletin of the Seismological Society of America ◽

10.1785/bssa0290030427 ◽

1939 ◽

Vol 29 (3) ◽

pp. 427-462 ◽

Cited By ~ 3

Author(s):

Perry Byerly

Keyword(s):

Least Squares ◽

Travel Time ◽

Sierra Nevada ◽

Accurate Determination ◽

Depth Of Focus ◽

Surface Layers ◽

P Waves ◽

Central California ◽

The Waves

Summary Least-squares adjustments of observations of waves of the P groups at central and southern California stations are used to obtain the speeds of various waves. Only observations made to tenths of a second are used. It is assumed that the waves have a common velocity for all earthquakes. But the time intercepts of the travel-time curves are allowed to be different for different shocks. The speed of P̄ is found to be 5.61 km/sec.±0.05. The speed for S̄ (founded on fewer data) is 3.26 km/sec. ± 0.09. There are slight differences in the epicenters located by the use of P̄ and S̄ which may or may not be significant. It is suggested that P̄ and S̄ may be released from different foci. The speed of Pn, the wave in the top of the mantle, is 8.02 km/sec. ± 0.05. Intermediate P waves of speeds 6.72 km/sec. ± 0.02 and 7.24 km/sec. ± 0.04 are observed. Only the former has a time intercept which allows a consistent computation of structure when considered a layer wave. For the Berkeley earthquake of March 8, 1937, the accurate determination of depth of focus was possible. This enabled a determination of layering of the earth's crust. The result was about 9 km. of granite over 23 km. of a medium of speed 6.72 km/sec. Underneath these two layers is the mantle of speed 8.02 km/sec. The data from other shocks centering south of Berkeley would not fit this structure, but an assumption of the thickening of the granite southerly brought all into agreement. The earthquakes discussed show a lag of Pn as it passes under the Sierra Nevada. This has been observed before. A reconsideration of the Pn data of the Nevada earthquake of December 20, 1932, together with the data mentioned above, leads to the conclusion that the root of the mountain mass projects into the mantle beneath the surface layers by an amount between 6 and 41 km.

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Accelerating numerical wave propagation using wavefield adapted meshes. Part I: forward and adjoint modelling

Geophysical Journal International ◽

10.1093/gji/ggaa058 ◽

2020 ◽

Vol 221 (3) ◽

pp. 1580-1590 ◽

Cited By ~ 3

Author(s):

M van Driel ◽

C Boehm ◽

L Krischer ◽

M Afanasiev

Keyword(s):

Wave Propagation ◽

Adaptive Mesh Refinement ◽

Waveform Inversion ◽

Computational Cost ◽

Model Space ◽

Adaptive Mesh ◽

Order Of Magnitude ◽

Speed Up ◽

Adjoint Modelling ◽

The Waves

SUMMARY An order of magnitude speed-up in finite-element modelling of wave propagation can be achieved by adapting the mesh to the anticipated space-dependent complexity and smoothness of the waves. This can be achieved by designing the mesh not only to respect the local wavelengths, but also the propagation direction of the waves depending on the source location, hence by anisotropic adaptive mesh refinement. Discrete gradients with respect to material properties as needed in full waveform inversion can still be computed exactly, but at greatly reduced computational cost. In order to do this, we explicitly distinguish the discretization of the model space from the discretization of the wavefield and derive the necessary expressions to map the discrete gradient into the model space. While the idea is applicable to any wave propagation problem that retains predictable smoothness in the solution, we highlight the idea of this approach with instructive 2-D examples of forward as well as inverse elastic wave propagation. Furthermore, we apply the method to 3-D global seismic wave simulations and demonstrate how meshes can be constructed that take advantage of high-order mappings from the reference coordinates of the finite elements to physical coordinates. Error level and speed-ups are estimated based on convergence tests with 1-D and 3-D models.

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Demonstration and application of diffusive and ballistic wave propagation for drone-to-ground and drone-to-drone wireless communications

Scientific Reports ◽

10.1038/s41598-020-71733-0 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Peter J. Burke

Keyword(s):

Wave Propagation ◽

Electromagnetic Wave ◽

Path Loss ◽

Base Station ◽

Physical Models ◽

Mapping Technology ◽

Aerial Vehicle ◽

A Cell ◽

Independent Path ◽

The Waves

Abstract In order to determine how an electromagnetic wave propagates from a base station to a cell phone or a wirelessly connected device, we use a novel Unmanned Aerial Vehicle (UAV) mapping technology to map the cellular network coverage at various altitudes in various terrains (flat, hilly, mountainous). For the flat terrains, the waves are shown to propagate ballistically: They have an altitude independent path loss consistent with minimal scatter in the propagation from transmitter to (aerial) receiver. In mountainous terrain, the waves are shown to propagate in the diffuse regime, and demonstrate a 10 dB increase in received signal intensity per 100′ of altitude gain, up to 400′. In the intermediate case, evidence of coherent wave interference is clearly observed in altitude independent interference patterns. These general observations can be used to build a physical or empirical model for drone-to-ground and drone-to-drone propagation, for which existing models are shown to fail. While important for building physical models of wave propagation in wireless networks, this method can be used more generally to determine the magnitude and phase of an electromagnetic wave at every point in space, as well as usher in the era of drone-to-ground and drone-to-drone communications.

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YUKAWA COUPLINGS FOR BOSONIC ZN ORBIFOLDS: THEIR MODULI AND TWISTED SECTOR DEPENDENCE

Modern Physics Letters A ◽

10.1142/s0217732392002457 ◽

1992 ◽

Vol 07 (33) ◽

pp. 3059-3070 ◽

Cited By ~ 34

Author(s):

S. STIEBERGER ◽

D. JUNGNICKEL ◽

J. LAUER ◽

M. SPALIŃSKI

Keyword(s):

Correlation Functions ◽

Target Space ◽

Twisted Sector ◽

Yukawa Couplings ◽

Point Correlation ◽

Field Correlation ◽

Twist Fields

The three-point correlation functions with twist fields are determined for bosonic ZN orbifolds. Both the choice of the modular background (compatible with the twist) and of the (higher) twisted sectors involved are fully general. We point out a necessary restriction on the set of instantons contributing to twist field correlation functions not obtained in previous calculations. Our results show that the theory is target space duality invariant.

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Rayleigh surface waves along the boundary between a plasma and a metallic screen

Journal of Plasma Physics ◽

10.1017/s0022377800016949 ◽

1993 ◽

Vol 49 (2) ◽

pp. 227-235 ◽

Cited By ~ 6

Author(s):

S. T. Ivanov ◽

K. M. Ivanova ◽

E. G. Alexov

Keyword(s):

Wave Propagation ◽

Electromagnetic Wave ◽

Surface Waves ◽

Electromagnetic Waves ◽

Electromagnetic Wave Propagation ◽

Cyclotron Frequency ◽

Plasma Frequency ◽

Magnetoactive Plasma ◽

Rayleigh Surface Waves ◽

The Waves

Electromagnetic wave propagation along the interface between a magnetoactive plasma and a metallic screen is investigated analytically and numerically. It is shown that the waves have a Rayleigh character: they are superpositions of two partial waves. It is concluded that electromagnetic waves propagate only at frequencies lower than min (ωp, ωc), where ωpis the plasma frequency and ωcis the cyclotron frequency. The field topology is found, and the physical character of the waves is discussed.

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