Cross Shot Line Surface Wave Tomography for Near-Surface Heterogeneity Detection
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Solution Overview
Problem
Current seismic mapping techniques struggle to accurately detect small near-surface heterogeneities, such as sinkholes, between receiver lines due to one-dimensional assumptions that ignore data violating these assumptions, resulting in incomplete surface wave analysis and inability to discern smaller heterogeneities.
Innovation Solution
The implementation of cross shot line surface wave tomography using 2D tomographic inversion to generate a shear wave velocity model, which incorporates data from multiple surface wave ray paths and produces a 3D dispersion volume representing spatial variations in seismic surface wave propagation, allowing for the detection of small heterogeneities and providing higher resolution compared to P-wave tomography.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If one-dimensional assumptions are used in seismic mapping, then the processing is simpler, but the detection of small near-surface heterogeneities between receiver lines is inaccurate
Solution Approach 1:
The patent transitions from one-dimensional surface wave analysis to two-dimensional tomographic inversion. By incorporating data from multiple ray paths including those between receiver lines, the method adds a spatial dimension to the analysis, enabling accurate detection of near-surface heterogeneities while maintaining computational efficiency through 2D rather than full 3D inversion.
2Measurement precision
If cross shot line surface wave tomography is used to detect small heterogeneities, then the detection accuracy improves, but the computational cost increases
Solution Approach 1:
The patent employs 2D tomographic inversion as a middle ground between simple 1D analysis and computationally intensive 3D tomography. This dimensional approach captures spatial variations in shear wave velocity including heterogeneities between receiver lines, while keeping computational requirements manageable by avoiding full 3D inversion.
Solution Approach 2:
The method substitutes P-wave tomography with S-wave (shear wave) tomography. Since surface waves are predominantly S-waves, this substitution provides higher resolution for near-surface heterogeneity detection while using the same 2D tomographic framework, optimizing the balance between detection accuracy and computational cost.
3Device complexity
If P-wave tomography is used, then the computational cost is lower, but the resolution for detecting near-surface heterogeneities is reduced
Solution Approach 1:
The patent replaces P-wave tomography with S-wave tomography based on surface wave data. Since surface waves are S-waves that travel along the ground surface and are more sensitive to near-surface conditions, this substitution provides higher resolution for detecting shallow heterogeneities while maintaining the computational efficiency of 2D tomographic inversion.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively maps near-surface conditions in subterranean formations, enabling the detection of small heterogeneities and providing a more accurate representation of subsurface velocity, improving the ability to identify features like karst and anomalous bodies, while being computationally cheaper than traditional 3D tomography.
Implementation Method 1
Seismic body waves travel into the ground, are reflected by subsurface formations, and return to the surface where they recorded by sensors called geophones
Implementation Method 2
Seismic surface waves travel along the ground surface and diminish as they get further from the surface. Seismic surface waves Rayleigh, Stoneley and Scholte surface waves are created at the interface between two media
Implementation Method 3
applying tomographic inversion to the filtered data to generate a dispersion map associated at the central frequency
Data Source
AI summary
Methods and systems for identifying near-surface heterogeneities in a subterranean formation using surface seismic arrays can include: recording raw seismic data using sensors at ground surface; applying a band bass filter to the raw seismic data using a central frequency; picking a phase arrival time for the filtered data; generating an initial starting phase velocity model for tomographic inversion from the raw seismic data; applying tomographic inversion to the filtered data to generate a dispersion map associated at the central frequency; repeating the applying a band bass filter, picking a phase arrival time, generating an initial starting velocity model, and applying tomographic inversion steps for each of a set of central frequencies; and generating a three-dimensional dispersion volume representing near-surface conditions in the subterranean formation by combining the dispersion maps.