Rayleigh Wave Tomography Sparse Grid Monitoring
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Solution Overview
Problem
Conventional seismic methods for monitoring near-surface structures are costly and impractical for continuous or long-term monitoring due to the need for dense grids of seismic sources and receivers, which limits their ability to detect thawing-induced compaction and deformation in frozen subsurface geological structures.
Innovation Solution
A method utilizing Rayleigh waves with a sparse acquisition grid, allowing for continuous monitoring with fewer seismic sources and receivers, which can be configured non-uniformly and used with low-frequency seismic sources to detect subsurface anomalies, enabling cost-effective long-term monitoring by analyzing travel times and phase delays to construct 3D models of subsurface structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dense grid of seismic sources and receivers is used for monitoring near-surface structures, then measurement precision and reliability are improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent extracts and utilizes only the Rayleigh wave component from the seismic signal, ignoring other wave types. By focusing specifically on surface waves and their dispersion characteristics, the method achieves reliable subsurface imaging without requiring the dense acquisition grids traditionally needed for full-waveform analysis
Solution Approach 2:
The patent employs inexpensive, temporary markers (such as colored flags or reflective targets) placed on the ground surface to assist in receiver positioning and orientation. These disposable markers eliminate the need for complex, permanent survey infrastructure while maintaining measurement precision during the monitoring period
2Reliability
If a dense grid of seismic sources and receivers is deployed for continuous monitoring, then detection reliability is improved, but loss of time and productivity worsen due to the weeks to months required for data acquisition
Solution Approach 1:
The patent enables continuous monitoring by deploying permanent or semi-permanent receiver arrays that remain in place over months or years. Once installed, these receivers continuously record Rayleigh wave signals from ambient sources (traffic, wind, etc.), eliminating the need for repeated time-consuming data acquisition campaigns while maintaining reliable detection capability
Solution Approach 2:
The system utilizes ambient seismic noise (traffic, wind, industrial activity) as the signal source, eliminating the need for active seismic sources. The environment itself provides the necessary vibrational energy, allowing receivers to continuously monitor subsurface changes without requiring external energy input or human intervention for signal generation
3Measurement precision
If classic seismic approaches are used for near-surface monitoring, then measurement precision is maintained, but cost increases make continuous monitoring impractical
Solution Approach 1:
The patent replaces expensive active seismic sources (vibrators, explosives) with passive ambient noise sources. By utilizing naturally occurring vibrations from traffic, wind, and industrial activity, the system eliminates the need for costly mechanical or chemical energy input while maintaining sufficient signal quality for accurate subsurface imaging through Rayleigh wave analysis
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 significantly reduces costs and enables continuous monitoring of subsurface structures over extended periods, providing effective detection of thawing-induced compaction and deformation, and can be applied to other underground anomalies, such as hydrocarbon reservoir depletion.
Implementation Method 1
Rayleigh waves are surface waves that can travel as ripples along or near the surface of the earth
Implementation Method 2
During a seismic survey, seismic sources generate Rayleigh waves along with other types of waves
Implementation Method 3
a method for monitoring near-surface structures using Rayleigh waves... analyzing travel times and phase delays to construct 3D models of subsurface structures
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
Method and system for ongoing monitoring for underground structure at or near a production wellpad is provided. The system includes a sparse acquisition grid and utilizes information obtained from Rayleigh waves to monitor subsurface structures.