The challenge
Identifying subtle faults
Modern underground coal mining requires specific information about geological faults, dykes and other structural features.
Even a fault with a ‘throw’ of a few metres can create safety issues and lead to costly delays in mine production.
Seismic (or vibration) data is a widely-used geophysical method to image subsurface environments.
To ensure there are no unwelcome surprises concerning coal seam conditions during mining, seismic-reflection surveys, due to their unprecedented ability to detect geological structures, have been widely used by Australian coal mines.
Locating faults with throws greater than 5-10 metres has been the generally accepted standard for seismic surveys.
However, the ability for exploration programs to locate the more subtle faults, shears and features is still a challenge in the coal mining industry.
Our response
The power of diffraction
Faults generate diffraction patterns in seismic waves i.e. changes in the wave pattern caused by an obstacle or opening.
Diffraction patterns have been used to detect faulting, especially for small faults.
Until recently, most data processing ignored these diffractions.
However, our research has shown diffractions in seismic data can provide a new way to detect small faults and other structures.
The most important step in diffraction imaging involves the extraction of relatively weak diffraction events from stronger seismic reflection signals.
We have developed a diffraction extraction approach which can be applied to both 2D and 3D seismic data.
The results
Small fault detection enhances mine safety and productivity
Using our refraction data analysis technique we have been able to detect small faults and other minor features undetectable using conventional reflection seismology.
The potential for a diffraction analysis to reveal the locations of small faults and dykes that can impact on underground coal mine operations has significant implication for mine safety and productivity.
For example, unexpected small geological structures within a longwall panel may damage cutting machines and stop mining.
We continue to develop advanced processing algorithms to utilise diffraction imaging for improved detection of small geological structures.