Teleseismic tomography: Equation one is wrong

2022 ◽  
Author(s):  
B.R. Julian ◽  
G.R. Foulger
Keyword(s):  
Incident Wave ◽  
Seismic Tomography ◽  
Local Structure ◽  
Observation Point ◽  
Wave Direction ◽  
Unknown Parameters ◽  
Teleseismic Tomography ◽  
Local Earthquake ◽  
Unknown Structure ◽  
Order Change

ABSTRACT Seismic tomography methods that use waves originating outside the volume being studied are subject to bias caused by unknown structure outside this volume. The bias is of the same mathematical order and similar magnitude as the local-structure effects being studied; failure to account for it can significantly corrupt derived structural models. This bias can be eliminated by adding to the inverse problem three unknown parameters specifying the direction and time for each incident wave, a procedure analogous to solving for event locations in local-earthquake and whole-mantle tomography. The forward problem is particularly simple: The first-order change in the arrival time at an observation point resulting from a perturbation to the incident-wave direction and time equals the change in the time of the perturbed incident wave at the point where the unperturbed ray entered the study volume. This consequence of Fermat’s principle apparently has not previously been recognized. Published teleseismic tomography models probably contain significant artifacts and need to be recomputed using the more complete theory.

Magma system beneath Tengchong volcanic zone inferred from local earthquake seismic tomography

2019 ◽  
Vol 377 ◽  
pp. 1-16 ◽  
Author(s):  
Yujin Hua ◽  
Shuangxi Zhang ◽  
Mengkui Li ◽  
Tengfei Wu ◽  
Chenyang Zou ◽  
...  
Keyword(s):  
Seismic Tomography ◽  
Volcanic Zone ◽  
Local Earthquake ◽  
Magma System

Inferring earth structure from combined measurements of rotational and translational ground motions

Geophysics ◽  
2009 ◽  
Vol 74 (6) ◽  
pp. WCD41-WCD47 ◽  
Author(s):  
Moritz Bernauer ◽  
Andreas Fichtner ◽  
Heiner Igel
Keyword(s):  
Seismic Tomography ◽  
Wave Speed ◽  
Ground Motions ◽  
Regional Scale ◽  
S Wave ◽  
Tomographic Images ◽  
Teleseismic Tomography ◽  
Local Structures ◽  
Novel Variant ◽  
Definition Of

We introduce a novel variant of seismic tomography that is based on colocated measurements of rotational and translational ground motions. Our aim is to assess whether rotations may be incorporated successfully into seismic inverse problems to produce better resolved and more realistic tomographic images. Our methodology is based on the definition of apparent S-wave speed as the ratio of rms velocity and rotation amplitudes. The principal advantages of this definition are that (1) no traveltimes measurements are needed and (2) the apparent S-wave speed is independent of source magnitude and source timing. We derive finite-frequency kernels for apparent S-wave speed by using a combination of the adjoint method and ray approximation. The properties of these kernels as a function of frequency bandwidth can be illustrated along with their usefulness for seismic tomography. In multifrequency synthetic inversions, we consider local crosshole tomography and regional-scale earthquake tomography. Our results indicate that S-wave speed variations can be retrieved accurately from colocated rotation and translation measurements, suggesting that our methodology is a promising extension of conventional seismic tomography. Further, apparent S-wave speed can be used to increase vertical resolution in teleseismic tomography for local structures.

RESEARCH ON THE WAVE-INDUCED SHIP MOTIONS IN FRONT OF DIFFERENT TYPES OF WHARF

2005 ◽  
Vol 19 (28n29) ◽  
pp. 1731-1734
Author(s):  
YAN BAO LI ◽  
XUE LIAN JIANG
Keyword(s):  
Wave Height ◽  
Incident Wave ◽  
Ship Motions ◽  
Design Codes ◽  
Wave Direction ◽  
Green Function Method ◽  
Frequency Wave ◽  
Different Types ◽  
Current Design ◽  
Wave Induced

One important function of the port is to protect ship or some other facilities from wave attack so as to stably handle cargoes. In current design codes, there are mainly two expressions of the tranquility standard of harbor basin: one is the acceptable wave height in front of wharf; the other is the tolerable amplitude of ship motion. However, ship motions are affected by some more factors simultaneously, such as wave frequency, wave height, incident wave direction, ship properties and wharf type. This paper presents some computed results of the wave-induced ship motions on the basis of a port case in China. First, the Simple Green Function method is employed to solve and compare the 2-dimension hydrodynamic coefficients in front of open or bulkhead wharf. The results show a great difference between them. Then, this paper computes and discusses the ship motions in front of open wharf at different wave frequencies and incident wave directions.

Possible sources of hydrothermal activity and mud volcanism in southern Sakhalin inferred from local earthquake seismic tomography

2017 ◽  
Vol 18 (5) ◽  
pp. 1943-1958 ◽  
Author(s):  
Ivan Koulakov ◽  
Aleksander S. Serdyukov ◽  
Alexey V. Konovalov ◽  
Valentin I. Mikhailov ◽  
Dmitry A. Safonov ◽  
...  
Keyword(s):  
Seismic Tomography ◽  
Hydrothermal Activity ◽  
Southern Sakhalin ◽  
Mud Volcanism ◽  
Local Earthquake

Hydrodynamic Analysis of Oil Storage Vessels for National Strategic Petroleum Reserve

2011 ◽  
Vol 291-294 ◽  
pp. 2541-2551
Author(s):  
Gang Jun Zhai ◽  
Yong Cheng ◽  
Wen Hua Wang ◽  
Yi Huang
Keyword(s):  
Incident Wave ◽  
Vertical Direction ◽  
Time History ◽  
Wave Force ◽  
Mooring System ◽  
Wave Direction ◽  
Storage Vessel ◽  
Oil Storage ◽  
Motion Responses ◽  
Incident Wave Direction

This paper expatiates hydrodynamic time-domain analysis on strategic oil storage vessels in free floating condition or with dolphin-fender mooring system by means of AQWA numerical software. The results indicate that motion responses of the oil storage vessel with dolphin-fender mooring have improved significantly. The time-history of wave diffraction forces in incident wave direction are basically consistent between the free floating and moored condition. However, in vertical direction of incident wave, the diffraction wave force of the oil storage vessel in free floating condition is obviously different from that with mooring system, which is the result of the coupling interaction between dolphin and vessels. Mooring forces include fender reaction and cable tension, as for which dominate, it depend on evocable motion responses about incident wave direction.

Homogeneous near-perfect invisible ground and free space cloak

2017 ◽  
Vol 31 (09) ◽  
pp. 1750059 ◽  
Author(s):  
Mohamad Fazeli ◽  
Seyyed Hassan Sedighy ◽  
Hamid Reza Hassani
Keyword(s):  
Incident Wave ◽  
Free Space ◽  
Single Step ◽  
Wave Direction ◽  
Transformation Theory ◽  
Design Flexibility ◽  
Mapping Process ◽  
Optical Transformation ◽  
Constitutive Parameters ◽  
Incident Wave Direction

A general approach to design near perfect invisible ground and free space cloaks is introduced in this paper. The proposed method which is based on the optical transformation theory, leads to homogeneous constitutive parameters for the cloaks without any singularities. Moreover, the single-step mapping process with linear relations achieves an uncomplicated designing process. Invisibility performance obtained by using this approach does not depend on the incident wave direction, also. The simplicity and design flexibility of the introduced approach with the homogeneity of extracted parameters greatly facilitate the design and fabrication processes of the both proposed ground and free space invisible cloaks. The numerical simulations prove the capability and universality of the proposed design approach.

scholarly journals Conceptual-based design of an ultrabroadband microwave metamaterial absorber

2021 ◽  
Vol 118 (36) ◽  
pp. e2110490118
Author(s):  
Sichao Qu ◽  
Yuxiao Hou ◽  
Ping Sheng
Keyword(s):  
Incident Wave ◽  
Impedance Matching ◽  
Hierarchical Structures ◽  
Normal Incidence ◽  
Metamaterial Absorber ◽  
Wave Direction ◽  
Minimum Thickness ◽  
Lateral Plane ◽  
Metallic Ring ◽  
Microwave Regime

By introducing metallic ring structural dipole resonances in the microwave regime, we have designed and realized a metamaterial absorber with hierarchical structures that can display an averaged −19.4 dB reflection loss (∼99% absorption) from 3 to 40 GHz. The measured performance is independent of the polarizations of the incident wave at normal incidence, while absorption at oblique incidence remains considerably effective up to 45°. We provide a conceptual basis for our absorber design based on the capacitive-coupled electrical dipole resonances in the lateral plane, coupled to the standing wave along the incident wave direction. To realize broadband impedance matching, resistive dissipation of the metallic ring is optimally tuned by using the approach of dispersion engineering. To further extend the absorption spectrum to an ultrabroadband range, we employ a double-layer self-similar structure in conjunction with the absorption of the diffracted waves at the higher end of the frequency spectrum. The overall thickness of the final sample is 14.2 mm, only 5% over the theoretical minimum thickness dictated by the causality limit.

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