scholarly journals A near-surface seismic scattered wave separation method

2014 ◽  
Vol 41 (6) ◽  
pp. 771-777 ◽  
Author(s):  
Jixiang XU ◽  
B F McLean ◽  
Xuejuan SONG
Keyword(s):  
Scattered Wave ◽  
Separation Method ◽  
Near Surface ◽  
Wave Separation

Tracking of velocity variations at depth in the presence of surface velocity fluctuations

Geophysics ◽  
2013 ◽  
Vol 78 (1) ◽  
pp. U1-U8 ◽  
Author(s):  
Benoit de Cacqueray ◽  
Philippe Roux ◽  
Michel Campillo ◽  
Stefan Catheline
Keyword(s):  
Surface Waves ◽  
Body Waves ◽  
Surface Velocity ◽  
Small Scale ◽  
Beam Forming ◽  
Near Surface ◽  
Velocity Fluctuations ◽  
Wave Separation ◽  
Double Beam ◽  
Velocity Variations

We tested a small-scale experiment that is dedicated to the study of the wave separation algorithm and to the velocity variations monitoring problem itself. It handles the case in which velocity variations at depth are hidden by near-surface velocity fluctuations. Using an acquisition system that combines an array of sources and an array of receivers, coupled with controlled velocity variations, we tested the ability of beam-forming techniques to track velocity variations separately for body waves and surface waves. After wave separation through double beam forming, the arrival time variations of the different waves were measured through the phase difference between the extracted wavelets. Finally, a method was tested to estimate near-surface velocity variations using surface waves or shallow reflection and compute a correction to isolate target velocity variations at depth.

scholarly journals Numerical and Experimental Research on Identifying a Delamination in Ballastless Slab Track

Materials ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 1788 ◽  
Author(s):  
Guopeng Fan ◽  
Haiyan Zhang ◽  
Wenfa Zhu ◽  
Hui Zhang ◽  
Xiaodong Chai
Keyword(s):  
Surface Wave ◽  
Linear Array ◽  
Point Contact ◽  
Scattered Wave ◽  
Lateral Resolution ◽  
Near Surface ◽  
Slab Track ◽  
Computational Performance ◽  
Significant Difference ◽  
Longitudinal Resolution

This paper aims to adopt the total focusing method (TFM) and wavenumber method for characterizing a delamination in ballastless slab track. Twelve dry point contact (DPC) transducers located at the upper surface of the slab track compose a linear array. These transducers are employed to actuate shear waves, which are suitable for identifying the delamination. The technique of removing the surface wave has been implemented for only retaining the scattered wave caused by the delamination and the reflected wave from the bottom of bed plate. Numerical and experimental results demonstrate that the delamination and bottom of the bed plate can be identified by the proposed methods. Furthermore, the near-surface pseudomorphism is distinctly restrained after removing the surface wave. Compared to TFM, the wavenumber method has the great advantages of improving computational performance and lateral resolution. However, they have no significant difference in the longitudinal resolution. Furthermore, it has been confirmed that the lateral resolution can be affected by the amount of transducers. This paper can provide valuable suggestions on improving the computational performance and the imaging accuracy when we identify a delamination in ballastless slab track.

The Suppression Technique of Near-surface Scattered Wave in Mountain Seismic Exploration

2016 ◽  
Author(s):  
Jixiang Xu* ◽  
Huajuan Cui ◽  
Shitai Dong ◽  
Xiping Sun ◽  
Shanglin Liang
Keyword(s):  
Scattered Wave ◽  
Seismic Exploration ◽  
Near Surface ◽  
Suppression Technique

Separation Research of Ultrasonic Wave in Transformer Partial Discharge Based on Improved Waveform Matching

2013 ◽  
Vol 291-294 ◽  
pp. 2325-2330
Author(s):  
Hong Ling Xie ◽  
Fei Wang ◽  
Yan Qing Li ◽  
Fei Long Wang
Keyword(s):  
Ultrasonic Wave ◽  
Attenuation Coefficient ◽  
Partial Discharge ◽  
Ultrasonic Sensor ◽  
Separation Method ◽  
Signal Frequency ◽  
Direct Wave ◽  
Wave Signal ◽  
Position Accuracy ◽  
Wave Separation

The use of direct wave to locate the position of the PD source is of better accuracy in transformer partial discharge ultrasound array positioning. For the signal received by ultrasonic sensor is consisted by direct wave, non-direct wave and a variety of noise, a direct wave separation method based on improved waveform matching is proposed in this paper. It is considered that the direct wave first reaches the ultrasonic sensor. A benchmarks triangle is built and then the attenuation coefficient and the signal frequency are both calculated. In order to search the matching wave, the benchmarks triangle is to pan and zoom. Finally, the best matching waveform is selected from a large number of matching waveforms as a direct wave signal. The result of simulation shows that the method can isolate the ultrasonic direct wave signal from the received signal, which provides some theoretical guidance to improve the position accuracy of the PD source.

Near-surface scattered waves enhancement with source-receiver interferometry

Geophysics ◽  
2018 ◽  
Vol 83 (6) ◽  
pp. Q49-Q69
Author(s):  
Jixiang Xu ◽  
Shitai Dong ◽  
Huajuan Cui ◽  
Yan Zhang ◽  
Ying Hu ◽  
...  
Keyword(s):  
Seismic Data ◽  
Seismic Waves ◽  
Scattered Wave ◽  
Receiver Functions ◽  
Surface Velocity ◽  
Seismic Exploration ◽  
Common Source ◽  
Constructive Interference ◽  
Near Surface ◽  
The Common

Near-surface scattered waves (NSWs) are the main noise in seismic data in areas with a complex near surface and can be divided into surface-to-surface scattered waves and body-to-surface scattered waves. We have developed a method for NSW enhancement that uses modified source-receiver interferometry. The method consists of two parts. First, deconvolutional intersource interferometry is used to cancel the common raypath of seismic waves from a near-surface scatterer to the common receiver and the receiver function. Second, convolutional interreceiver interferometry is used to compensate the common raypath of seismic waves from the common source to the near-surface scatterer and the source function. For an isotropic point scatterer near the earth’s surface in modified source-receiver interferometry, a body-to-surface scattered wave can be reconstructed by constructive interference not only among three body-to-surface scattered waves but also among a body-to-surface scattered wave and two surface-to-surface scattered waves; a surface-to-surface scattered wave can be reconstructed by constructive interference not only among three surface-to-surface scattered waves but also among a surface-to-surface scattered wave and two body-to-surface scattered waves. According to stationary phase analysis based on the superposition principle, we have developed a so-called dual-wheel driving configuration of modified source-receiver interferometry for enhancing NSWs in the data of conventional seismic exploration. The main advantages of the scheme are that (1) it can be used to enhance NSWs without the need for any a priori knowledge of topography and near-surface velocity, (2) it can be used to reconstruct NSWs from real sources to real receivers, including 3D near-surface side-scattered waves, and (3) it can be applied to conventional seismic data with finite-frequency bandwidth, spatially limited and sparse arrays, different source and receiver functions, and static correction. Numerically simulated data and field seismic data are used to demonstrate the feasibility and effectiveness of the scheme.

scholarly journals Suppressing near-receiver scattered waves from seismic land data

Geophysics ◽  
2006 ◽  
Vol 71 (4) ◽  
pp. S121-S128 ◽  
Author(s):  
Xander H. Campman ◽  
Gérard C. Herman ◽  
Everhard Muyzert
Keyword(s):  
Field Data ◽  
Surface Region ◽  
Scattered Wave ◽  
Surface Heterogeneity ◽  
Body Waves ◽  
Surface Scattering ◽  
Data Set ◽  
Processing Scheme ◽  
Near Surface ◽  
Data Record

Upgoing body waves that travel through a heterogeneous near-surface region can excite scattered waves. When the scattering takes place close to the receivers, secondary waves interfere with the upcoming reflections, diminishing the continuity of the wavefront. We estimate a near-surface scattering distribution from a subset of a data record and use this scattering distribution to predict the secondary waves of the entire data record with a wave-theoretical model for near-receiver scattering. We then subtract the predicted scattered waves from the record to obtain the wavefield that would have been measured in the absence of near-surface heterogeneities. We apply this method to part of a field data set acquired in an area with significant near-surface heterogeneity. The main result of our processing scheme is that we effectively remove near-surface scattered waves. This, in turn, increases trace-to-trace coherence of reflection events. Moreover, application of our method improves the results obtained from just an application of a dip filter because we remove parts of the scattered wave with apparent velocities that are typically accepted by the pass zone of the dip filter. Based on these results, we conclude that our method for suppressing near-receiver scattered waves works well on densely sampled land data collected in areas with strong near-surface heterogeneity.

Evaluation of Nonlinear Wave Separation Method to Assess Reflection Transit Time: A Virtual Patient Study

2021 ◽  
Author(s):  
Rahul Manoj ◽  
V Raj Kiran ◽  
P M Nabeel ◽  
Mohanasankar Sivaprakasam ◽  
Jayaraj Joseph
Keyword(s):  
Nonlinear Wave ◽  
Transit Time ◽  
Virtual Patient ◽  
Separation Method ◽  
Patient Study ◽  
Wave Separation

Backward wave separation method in a single transmitter and multi-receiver sensor array for improved damage identification of two-dimensional structures

2017 ◽  
Vol 26 (2) ◽  
pp. 229-250 ◽  
Author(s):  
Zijian Wang ◽  
Pizhong Qiao
Keyword(s):  
Sensor Array ◽  
Damage Identification ◽  
Signal To Noise Ratio ◽  
Metal Plate ◽  
Separation Method ◽  
High Signal ◽  
Localization Accuracy ◽  
Reflected Wave ◽  
Wave Separation ◽  
Backward Wave

In this paper, a backward wave separation method is proposed. Since the first backward wave can be considered as the damage reflection, the damage reflected wave peaks are artificially amplified by appropriately shifting and summing signals collected from a series of sensing points aligned along the wave propagating direction. This shifting and summing process aims to present the damage reflected wave peaks more distinctively while offsets randomly distributed environmental interferences. Due to the high signal-to-noise ratio of the treated signal, the application of backward wave separation is able to attain baseline-free damage detection. A circular single transmitter and multi-receiver sensor array is then deployed on a metal plate to identify the crack-like damage. Signals collected by the sensor array with and without the treatment of the backward wave separation method are, respectively, imported to the delay-and-sum imaging algorithm to yield individual damage contours. The comparisons between these contours demonstrate that the backward wave separation method is able to significantly improve the damage identification performance of the sensor array with respect to the damage localization accuracy, noise immunity, and damage sensitivity. Both the finite element modeling and laser measurement are conducted to validate the effectiveness of the proposed backward wave separation method.

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