P- and S-wave energy flux density vectors

The cross-correlation imaging condition between source- and receiver-wavefields is often used in the elastic wave reverse-time migration (RTM) to utilize P- and S-waves. However, it cannot be applied in the absence of source information (e.g., source location, and source wavelet), which is quite common in passive source exploration. We employ a source-free P-SV converted-wave imaging condition, which only requires the back-propagating receiver-wavefield to utilize the P-SV converted waves in imaging the subsurface structures. The imaging condition is independent of source information, which can avoid the extrapolation and reconstruction of the source-wavefield. As a result, the computational cost is decreased to about one-third of conventional RTM that uses source-wavefield reconstruction strategies, e.g., random boundaries. The memory requirement could be also reduced by avoiding the calculation of source-wavefield. Because our imaging condition uses the vector P-wavefield and vector S-wavefield to utilize the P-SV waves, it is necessary to decouple P-wavefield and S-wavefield during the reverse-time extrapolation of receiver-wavefield. We use the first-order velocity-dilatation-rotation elastic wave equations to realize the reverse-time propagation of vector receiver-wavefield, where the vector P-wavefield and vector S-wavefield can be obtained directly. Based on the above methods, a source-free P-SV converted-wave RTM of multi-component seismic data is realized. The model tests show that this method can generate promising subsurface images and can be complementarily used when conventional cross-correlation imaging conditions are not suitable.

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“…The three-dimension first-order velocity-dilatation-rotation equations in an isotropic medium are (Tang et al, 2016):…”

Section: Reverse-time Extrapolation Of First-order Velocity-dilatation-rotation Elastic Wave Equationsmentioning

confidence: 99%

“…According to the definition of the Poynting vector in seismic wavefield (Yoon and Marfurt, 2006), the following equations can be used to calculate the Poynting vector of pure P-and S-waves in the wavefield extrapolation using Eq. 1 (Tang et al, 2016):…”

Section: Obtaining the Poynting Vector Of Pure Pand S-waves In The Reverse-time Extrapolationmentioning

confidence: 99%

Source-Free P-SV Converted-Wave Reverse-Time Migration Using First-Order Velocity-Dilatation-Rotation Equations

Yao

Shao

2022

Front. Earth Sci.

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“…The carbon-based solid contact electrodes appear to perform better than the metal ones. 67Metal NPs, (68) graphene,(69) carbon nanofibers (CNF), (70) and molybdenum disulfide (MoS 2 )(71) are some of the materials that have been used to enhance the sensitivity of these electrodes. Other materials like nanoporous Pt-Ru alloy (72) and molecularly imprinted polymers (MIP) (73) have also been used successfully.…”

Section: Electrodes and Customized Devicesmentioning

confidence: 99%

“…Electrode surface modification with functional groups (−SH, −NH 2 , −CN) can coordinate metallic nanoparticles immobilization to create a multilayered nanocomposite modified electrode. Amine or thiol linkers, such as cysteamine, (68) polytyramine, (199) and thiourea SAM (46) create the foundation for Au NPs or Ag NPs immobilization. It is worth highlighting that Loyprasert et al(46) and Dawan et al(178) developed nanomaterial-modified electrodes flow-through capacitive immunosensors with extremely low detection limits for the detection of MC-LR.…”

Section: Recent Advances and Future Trendsmentioning

confidence: 99%

A Comprehensive Review: Development of Electrochemical Biosensors for Detection of Cyanotoxins in Freshwater

et al. 2019

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Cyanobacteria harmful algal blooms are increasing in frequency and cyanotoxins have become an environmental and public concern in the U.S. and worldwide. In this Review, the majority of reported studies and developments of electrochemical affinity biosensors for cyanotoxins are critically reviewed and discussed. Essential background information about cyanobacterial toxins and electrochemical biosensors is combined with the rapidly moving development of electrochemical biosensors for these toxins. Current issues and future challenges for the development of useful electrochemical biosensors for cyanotoxin detection that meet the demands for applications in field freshwater samples are discussed. The major aspects of the entire review article in a prescribed sequence include (i) the state-of-the-art knowledge of the toxicity of cyanotoxins, (ii) important harmful algal bloom events, (iii) advisories, guidelines, and regulations, (iv) conventional analytical methods for determination of cyanotoxins, (v) electrochemical transduction, (vi) recognition receptors, (vii) reported electrochemical biosensors for cyanotoxins, (viii) summary of analytical performance, and (ix) recent advances and future trends. Discussion includes electrochemical techniques and devices, biomolecules with high affinity, numerous array designs, various detection approaches, and research strategies in tailoring the properties of the transducer-biomolecule interface. Scientific and engineering aspects are presented in depth. This review aims to serve as a valuable source to scientists and engineers entering the interdisciplinary field of electrochemical biosensors for detection of cyanotoxins in freshwaters.

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“…; Wang and McMechan ; Tang et al . ; Lu and Liu ) is easy to calculate. However, they are not clean everywhere, especially at the overlapped points.…”

Section: Synthetic Tests For Anisotropic Ertmmentioning

confidence: 99%

Poynting and polarization vectors based wavefield decomposition and their application on elastic reverse time migration in 2D transversely isotropic media

Liu

Zhang

et al. 2019

Geophysical Prospecting

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A B S T R A C TWith the progress in computational power and seismic acquisition, elastic reverse time migration is becoming increasingly feasible and helpful in characterizing the physical properties of subsurface structures. To achieve high-resolution seismic imaging using elastic reverse time migration, it is necessary to separate the compressional (P-wave) and shear (S-wave) waves for both isotropic and anisotropic media. In elastic isotropic media, the conventional method for wave-mode separation is to use the divergence and curl operators. However, in anisotropic media, the polarization direction of P waves is not exactly parallel to the direction of wave propagation. Also, the polarization direction of S-waves is not totally perpendicular to the direction of wave propagation. For this reason, the conventional divergence and curl operators show poor performance in anisotropic media. Moreover, conventional methods only perform well in the space domain of regular grids, and they are not suitable for elastic numerical simulation algorithms based on non-regular grids. Besides, these methods distort the original wavefield by taking spatial derivatives. In this case, a new anisotropic wave-mode separation scheme is developed using Poynting vectors. This scheme can be performed in the angle domain by constructing the relationship between group and polarization angles of different wave modes. Also, it is performed pointwise, independent of adjacent space points, suitable for parallel computing. Moreover, there is no need to correct the changes in phase and amplitude caused by the derivative operators. By using this scheme, the anisotropic elastic reverse time migration is more efficiently performed on the unstructured mesh. The effectiveness of our scheme is verified by several numerical examples.

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P- and S-wave energy flux density vectors

Cited by 11 publications

References 10 publications

Source-Free P-SV Converted-Wave Reverse-Time Migration Using First-Order Velocity-Dilatation-Rotation Equations

Source-Free P-SV Converted-Wave Reverse-Time Migration Using First-Order Velocity-Dilatation-Rotation Equations

A Comprehensive Review: Development of Electrochemical Biosensors for Detection of Cyanotoxins in Freshwater

Poynting and polarization vectors based wavefield decomposition and their application on elastic reverse time migration in 2D transversely isotropic media

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