scholarly journals ESTIMATION OF MODEL UNCERTAINTY OF S-WAVE VELOCITY PROFILE FROM INVERSION OF SURFACE-WAVE PHASE VELOCITY USING MCMC METHOD

2014 ◽  
Vol 79 (706) ◽  
pp. 1795-1803 ◽  
Author(s):  
Hiroaki YAMANAKA
Keyword(s):  
Surface Wave ◽  
Velocity Profile ◽  
Phase Velocity ◽  
Wave Velocity ◽  
Model Uncertainty ◽  
Mcmc Method ◽  
S Wave ◽  
Wave Phase ◽  
Wave Phase Velocity

Estimations of formation velocity, permeability, and shear‐wave anisotropy using acoustic logs

Geophysics ◽  
1996 ◽  
Vol 61 (2) ◽  
pp. 437-443 ◽  
Author(s):  
Ningya Cheng ◽  
Chuen Hon Cheng
Keyword(s):  
Phase Velocity ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Stoneley Wave ◽  
S Wave ◽  
Acoustic Logging ◽  
Wave Phase ◽  
Wave Phase Velocity ◽  
Logging Tool

Field data sets collected by an array monopole acoustic logging tool and a shear wave logging tool are processed and interpreted. The P‐ and S‐wave velocities of the formation are determined by threshold detection with cross‐correlation correction from the full waveform and the shear‐wave log, respectively. The array monopole acoustic logging data are also processed using the extended Prony’s method to estimate the borehole Stoneley wave phase velocity and attenuation as a function of frequency. The well formation between depths of 2950 and 3150 ft (899 and 960 m) can be described as an isotropic elastic medium. The inverted [Formula: see text] from the Stoneley wave phase velocity is in excellent agreement with the shear‐wave log results in this section. The well formation between the depths of 3715 and 3780 ft (1132 and 1152 m) can be described as a porous medium with shear‐wave velocity anisotropy about 10% to 20% and with the symmetry axis perpendicular to the borehole axis. The disagreement between the shear‐wave velocity from the Stoneley wave inversion and the direct shear‐wave log velocity in this section is beyond the errors in the measurements. Estimated permeabilities from low‐frequency Stoneley wave velocity and attenuation data are in good agreement with the core measurements. Also it is proven that the formation permeability is not the cause of the discrepancy. From the estimated “shear/pseudo‐Rayleigh” phase velocities in the array monopole log and the 3-D finite‐difference synthetics in the anisotropic formation, the discrepancy can best be explained as shear‐wave anisotropy.

Decoupled approximation and separate extrapolation of P- and SV-waves in transversely isotropic media

Geophysics ◽  
2021 ◽  
pp. 1-57
Author(s):  
Bowen Li ◽  
Alexey Stovas
Keyword(s):  
Phase Velocity ◽  
Wave Velocity ◽  
Transversely Isotropic ◽  
P Wave ◽  
S Wave ◽  
Wave Phase ◽  
Wave Phase Velocity ◽  
Tti Media ◽  
Vti Media ◽  
Acoustic Approximation

Characterizing the kinematics of seismic waves in elastic vertical transversely isotropic (VTI) media involves four independent parameters. To reduce the complexity, the acoustic approximation for P-waves reduces the number of required parameters to three by setting the vertical S-wave velocity to zero. However, since only the SV-wave phase velocities parallel or perpendicular to the symmetry axis are indirectly set to zero, the acoustic approximation leads to coupled P-wave components and SV-wave artifacts. The new acoustic approximation suggests setting the vertical S-wave velocity as a phase angle-dependent variable so that the SV-wave phase velocity is zero at all phase angles. We find that manipulating this parameter is a valid way for P-wave approximation, but doing so inevitably leads to zero- or non-zero-valued spurious SV-wave components. Thus, we have developed a novel approach to efficiently approximate and thoroughly separate the two wave modes in VTI media. First, the exact P- and SV-wave phase velocity expressions are rewritten by introducing an auxiliary function. After confirming the insensitivity of this function, we construct a new expression for it and obtain simplified P- and SV-wave phase velocity expressions, which are three- and four-parameter, respectively. This approximation process leads to the same reasonable error for both wave modes. Accuracy analysis indicates that for the P-wave, the overall accuracy performance of our approach is comparable to that of some existing three-parameter approximations. We then derive the corresponding P- and SV-wave equations in tilted transversely isotropic (TTI) media and provide two available solutions, the hybrid finite-difference/pseudo-spectral scheme and the low-rank approach. Numerical examples illustrate the separability and high accuracy of the proposed P- and SV-wave simulation methods in TTI media.

S-wave velocity structure of the North China from inversion of Rayleigh wave phase velocity

2014 ◽  
Vol 88 ◽  
pp. 178-191 ◽  
Author(s):  
Hao-peng Chen ◽  
Liang-bao Zhu ◽  
Qing-dong Wang ◽  
Pan Zhang ◽  
Ying-hang Yang
Keyword(s):  
Phase Velocity ◽  
Rayleigh Wave ◽  
Wave Velocity ◽  
North China ◽  
Velocity Structure ◽  
S Wave ◽  
Wave Phase ◽  
The North ◽  
Wave Phase Velocity ◽  
Rayleigh Wave Phase Velocity

Ground roll: A potential tool for constraining shallow shear‐wave structure

Geophysics ◽  
1993 ◽  
Vol 58 (5) ◽  
pp. 713-719 ◽  
Author(s):  
Ghassan I. Al‐Eqabi ◽  
Robert B. Herrmann
Keyword(s):  
Surface Wave ◽  
Phase Velocity ◽  
Wave Velocity ◽  
Wave Structure ◽  
S Wave ◽  
Data Set ◽  
Velocity Inversion ◽  
Ground Roll ◽  
Lateral Variations ◽  
Wave Arrival

The objective of this study is to demonstrate that a laterally varying shallow S‐wave structure, derived from the dispersion of the ground roll, can explain observed lateral variations in the direct S‐wave arrival. The data set consists of multichannel seismic refraction data from a USGS-GSC survey in the state of Maine and the province of Quebec. These data exhibit significant lateral changes in the moveout of the ground‐roll as well as the S‐wave first arrivals. A sequence of surface‐wave processing steps are used to obtain a final laterally varying S‐wave velocity model. These steps include visual examination of the data, stacking, waveform inversion of selected traces, phase velocity adjustment by crosscorrelation, and phase velocity inversion. These models are used to predict the S‐wave first arrivals by using two‐dimensional (2D) ray tracing techniques. Observed and calculated S‐wave arrivals match well over 30 km long data paths, where lateral variations in the S‐wave velocity in the upper 1–2 km are as much as ±8 percent. The modeled correlation between the lateral variations in the ground‐roll and S‐wave arrival demonstrates that a laterally varying structure can be constrained by using surface‐wave data. The application of this technique to data from shorter spreads and shallower depths is discussed.

Surface-Wave Tomography of Eastern and Central Tibet from Two-Plane-Wave Inversion: Rayleigh-Wave and Love-Wave Phase Velocity Maps

2020 ◽  
Vol 110 (3) ◽  
pp. 1359-1371
Author(s):  
Lun Li ◽  
Yuanyuan V. Fu
Keyword(s):  
Surface Wave ◽  
Tibetan Plateau ◽  
Phase Velocity ◽  
Rayleigh Wave ◽  
Love Wave ◽  
The Tibetan Plateau ◽  
Surface Wave Tomography ◽  
Wave Phase ◽  
Wave Phase Velocity ◽  
Wave Tomography

ABSTRACT An understanding of mantle dynamics occurring beneath the Tibetan plateau requires a detailed image of its seismic velocity and anisotropic structure. Surface waves at long periods (>50  s) could provide such critical information. Though Rayleigh-wave phase velocity maps have been constructed in the Tibetan regions using ambient-noise tomography (ANT) and regional earthquake surface-wave tomography, Love-wave phase velocity maps, especially those at longer periods (>50  s), are rare. In this study, two-plane-wave teleseismic surface-wave tomography is applied to develop 2D Rayleigh-wave and Love-wave phase velocity maps at periods between 20 and 143 s across eastern and central Tibet and its surroundings using four temporary broadband seismic experiments. These phase velocity maps share similar patterns and show high consistency with those previously obtained from ANT at overlapping periods (20–50 s), whereas our phase velocity maps carry useful information at longer periods (50–143 s). Prominent slow velocity is imaged at periods of 20–143 s beneath the interior of the Tibetan plateau (i.e., the Songpan–Ganzi terrane, the Qiangtang terrane, and the Lhasa terrane), implying the existence of thick Tibetan crust along with warm and weak Tibetan lithosphere. In contrast, the dispersal of fast velocity anomalies coincides with mechanically strong, cold tectonic blocks, such as the Sichuan basin and the Qaidam basin. These phase velocity maps could be used to construct 3D shear-wave velocity and radial seismic anisotropy models of the crust and upper mantle down to 250 km across the eastern and central Tibetan plateau.

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