The echo of a fault or fracture

Geophysics ◽  
2000 ◽  
Vol 65 (1) ◽  
pp. 176-189 ◽  
Author(s):  
Geir U. Haugen ◽  
Michael A. Schoenberg
Keyword(s):  
Acoustic Scattering ◽  
Seismic Energy ◽  
Scattering Data ◽  
Isotropic Case ◽  
Fracture Characterization ◽  
Isotropic Media ◽  
Single Well ◽  
Analytical Formulae ◽  
Scattering Response ◽  
Physical Features

The seismic response of single faults, joints, or fractures of large planar extent is analyzed. These are modeled as nonwelded interfaces. In spite of the large range of scale, all are assumed to behave according to linear slip theory. Such a model has been considered theoretically and experimentally before. The aim of this paper is to give a physical interpretation to such a linear slip interface; to provide simple analytical formulae for the scattering response, even when the fracture is embedded in an anisotropic background medium; and to relate the properties of this scattering response, in the isotropic case, to the physical features of the fracture. The analysis shows that the reflectivity and transmissivity of the fracture depend on slowness along the fracture and on frequency. The frequency dependence arises from the fact that, even though the fracture is assumed to be an interface of zero thickness, it still has at least two characteristic widths that provide the length scales necessary for scattering dependence on wavelength. For isotropic media, the PP and SS reflections generally decrease in amplitude with increasing slowness along the fracture. At certain slowness values, they reach minima before starting to increase for still larger slownesses. The slowness value of these minima reveals the fracture compliances, from which inferences about the physical properties of the fracture may be drawn. Both forward modeling of the acoustic response of a fracture and the estimation of fracture properties from acoustic scattering data can benefit from the type of analysis presented here. The range of such problems extends from the scattering of earthquake‐generated seismic energy by major faults in the earth, through reservoir fracture characterization from single‐well sonic imaging, to the characterization of flaws or poorly bonded surfaces in ultrasonic nondestructive testing.

Single-well S-wave imaging using multicomponent dipole acoustic-log data

Geophysics ◽  
2009 ◽  
Vol 74 (6) ◽  
pp. WCA211-WCA223 ◽  
Author(s):  
Xiao-Ming Tang ◽  
Douglas J. Patterson
Keyword(s):  
Field Data ◽  
Wave Radiation ◽  
Dipole Source ◽  
Directional Sensitivity ◽  
S Wave ◽  
Fracture Characterization ◽  
Processing Application ◽  
S Waves ◽  
Wave Imaging ◽  
Single Well

Single-well S-wave imaging has several attractive features because of its directional sensitivity and usefulness for fracture characterization. To provide a method for single-well acoustic imaging, we analyzed the effects of wave radiation, reflection, and borehole acoustic response on S-wave reflection measurements from a multicomponent dipole acoustic tool. A study of S-wave radiation from a dipole source and the wave’s reflection from a formation boundary shows that the S-waves generated by a dipole source in a borehole have a wide radiation pattern that allows imaging of reflectors at various dip angles crossing the borehole. More importantly, the azimuthal variation of the S-waves, in connection with the multicomponent nature of a cross-dipole tool, can determine the strike of the reflector. We used our theoretical foundation for borehole S-wave imaging to formulate an inversion procedure for field data processing. Application to field data validates the theoretical results and demonstrates the advantages of S-wave imaging. Application to near-borehole fracture imaging clearly demonstrates S-wave azimuthal sensitivity to fracture orientation.

Fracture characterization from scattered seismic energy: A case study

2006 ◽  
Author(s):  
Samantha Grandi K. ◽  
Sung Yuh ◽  
Mark E. Willis ◽  
M. Nafi Toksöz
Keyword(s):  
Seismic Energy ◽  
Fracture Characterization

scholarly journals Inference of biological and physical parameters in an internal wave using multiple-frequency, acoustic-scattering data

2003 ◽  
Vol 60 (5) ◽  
pp. 1033-1046 ◽  
Author(s):  
Joseph D. Warren ◽  
Timothy K. Stanton ◽  
Peter H. Wiebe ◽  
Harvey E. Seim
Keyword(s):  
Internal Wave ◽  
Field Experiments ◽  
Gulf Of Maine ◽  
Acoustic Scattering ◽  
Primary Source ◽  
Theoretical Work ◽  
Scattering Data ◽  
Physical Parameters ◽  
Multiple Frequency ◽  
Scattering Spectra

Abstract High-frequency sound (>10 kHz) is scattered in the ocean by many different processes. In the water column, marine organisms are often assumed to be the primary source of acoustic backscatter. Recent field experiments and theoretical work suggest that the temperature and salinity microstructure in some oceanic regions could cause acoustic scattering at levels comparable to that caused by marine life. Theoretical acoustic-scattering models predict that the scattering spectra for microstructure and organisms are distinguishable from each other over certain frequency ranges. A method that uses multiple-frequency acoustic data to exploit these differences has been developed, making it possible to discriminate between biological and physical sources of scattering under some conditions. This method has been applied to data collected in an internal wave in the Gulf of Maine. For regions of the internal wave in which the dominant source of scattering is either biological or physical in origin, it is possible to combine the acoustic-scattering data and temperature and salinity profiles with acoustic-scattering models to perform a least-squares inversion. Using this approach, it is possible to estimate the dissipation rate of turbulent kinetic energy for some regions of the internal wave, and the length and numerical abundance of the dominant biological scatterer, euphausiids, in others.

A Novel Classification Method of Fish Based on Multi-Feature Fusion

2015 ◽  
Vol 713-715 ◽  
pp. 1513-1519 ◽  
Author(s):  
Wei Dong Du ◽  
Bao Wei Chen ◽  
Hai Sen Li ◽  
Chao Xu
Keyword(s):  
Discrete Cosine Transform ◽  
Feature Fusion ◽  
Acoustic Scattering ◽  
Scattering Data ◽  
Support Vector ◽  
Svm Classifier ◽  
Correct Identification ◽  
Classification Problems ◽  
Cosine Transform ◽  
Identification Rate

In order to solve fish classification problems based on acoustic scattering data, temporal centroid (TC) features and discrete cosine transform (DCT) coefficients features used to analyze acoustic scattering characteristics of fish from different aspects are extracted. The extracted features of fish are reduced in dimension and fused, and support vector machine (SVM) classifier is used to classify and identify the fishes. Three kinds of different fishes are selected as research objects in this paper, the correct identification rates are given based on temporal centroid features and discrete cosine transform coefficients features and fused features. The processing results of actual experimental data show that multi-feature fusion method can improve the identification rate at about 5% effectively.

Characterization of a cylindrical rod by inversion of acoustic scattering data

Ultrasonics ◽  
2014 ◽  
Vol 54 (6) ◽  
pp. 1559-1567 ◽  
Author(s):  
Mohammadreza Kari ◽  
Farhang Honarvar
Keyword(s):  
Acoustic Scattering ◽  
Scattering Data

Measuring the acoustic scattering response of small groups of live fish in a laboratory tank

2015 ◽  
Vol 137 (4) ◽  
pp. 2362-2362
Author(s):  
Maria P. Raveau ◽  
Christopher Feuillade ◽  
Gabriel Venegas ◽  
Preston S. Wilson
Keyword(s):  
Small Groups ◽  
Acoustic Scattering ◽  
Live Fish ◽  
Scattering Response ◽  
Laboratory Tank

Efficient wave-mode separation in vertical transversely isotropic media

Geophysics ◽  
2017 ◽  
Vol 82 (2) ◽  
pp. C35-C47 ◽  
Author(s):  
Yang Zhou ◽  
Huazhong Wang
Keyword(s):  
Transversely Isotropic ◽  
Wave Mode ◽  
Phase Changes ◽  
Isotropic Case ◽  
Conservation Of Energy ◽  
Mode Separation ◽  
Isotropic Media ◽  
Curl Operators ◽  
Vti Media ◽  
Poynting Vectors

Wave-mode separation can be achieved by projecting elastic wavefields onto mutually orthogonal polarization directions. In isotropic media, because the P-wave’s polarization vectors are consistent with wave vectors, the isotropic separation operators are represented by divergence and curl operators, which are easy to realize. In anisotropic media, polarization vectors deviate from wave vectors based on local anisotropic strength and separation operators lose their simplicity. Conventionally, anisotropic wave-mode separation is implemented either by direct filtering in the wavenumber domain or nonstationary filtering in the space domain, which are computationally expensive. Moreover, in conventional anisotropic separation, correcting for amplitude and phase changes of waveforms by applying separation operators is also more difficult than in an isotropic case. We have developed new operators for efficient wave-mode separation in vertical transversely isotropic (VTI) media. Our separation operators are constructed by local rotation of wave vectors to directions where the quasi-P (qP) wave is polarized. The deviation angles between the wave vectors and the qP-wave’s polarization vectors are explicitly estimated using the Poynting vectors. Obtaining polarization directions by rotating wave vectors yields separation operators in VTI media with the same forms as divergence and curl operators, except that the spatial derivatives are now rotated to implement wavefield projections in accurate polarization directions. The main increase in computational cost relative to isotropic separation operators is the estimation of the Poynting vectors, which is relatively small within elastic-wave extrapolation. As a result, applying the proposed operators is efficient. In the meantime, the waveforms corrections for divergence and curl operators can be directly extended for our new operators due to the similarities between these operators. By numerical exercises, we have determined that wave modes can be well-separated with small numerical cost using the present separation operators. The conservation of energy in wave-mode separation by applying waveform corrections was also verified.

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