Seismic fault detectability: a view from numerical modelling

Summary

Modern underground coal mining requires certainty about geological faults 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. In this paper, we investigate the detectability of small faults by the seismic reflection method through numerical modelling in an ideal noise-free environment with homogeneous layering. We find that 1) the smallest faults that can be identified in a 2D survey have throws of 1/8 of the wavelength; 2) faults are more difficult to detect when they occur within other structures.

In typical seismic exploration for coal mining, the dominant seismic frequency is about 100 Hz and the seismic velocity of the overburden ranges from 3000m/s to 4000m/s. The corresponding wavelength is 30m to 40m. This suggests that the detectability limit for faults is about 4 – 5m. However, in the case of 3D seismic surveying we suggest that this can be redefined to 1/16 of wavelength (2 - 2.5m) because of the benefits offered by computer-aided horizon identification and the improved spatial coherence in 3D seismic surveys. In all cases, the actual fault detectability will depend on the quality of the seismic data and the geology of the area under investigation.

Key words::

• Fault detection
• seismic surveying
• seismic resolution
• coal mining.