Microseismic monitoring

Microseismic monitoring is the recording, analysis and interpretation of micro-earthquakes whenever rock or geological materials fracture and fail. This can happen on a variety of scales from the acoustic emission caused by the movement of single particles in a landslide, the fracturing of ice in glaciers, failure of strata above and around underground excavations such as longwall coal mines or natural underground cavities, up to felt earthquakes, both man-made and tectonic. Analysis of three-component microseismic data can give the location of failure and detailed information about the mechanisms and parameters of the fracturing process. The group have applied this technique to the monitoring and predictions of outbursts in coal mines in the UK and Australia, landslide monitoring, hydro-fracture in hydrocarbon reservoirs and monitoring a variety of mining processes including coal, potash, gypsum and salt. The expertise gained here has also been applied to the characterisation and monitoring of low-frequency noise using combined microseismology, infrasound and acoustics.

Coal mine monitoring

The nature of caving behaviour in the vicinity of longwall extraction can be critical to the financial success of a colliery. Face support, interaction effects, optimum pillar design, subsidence at surface and control of water all depend critically on the distribution of fractures and stress induced by mining. Until now, there has been no method by which these effects could be observed.

Recent work by the Applied & Environmental Geophysics research group in collaboration with IMC Geophysics Ltd has provided a unique solution. Seismic detectors (geophones) are cemented into a small number of surface or in-mine boreholes surrounding the mining district, and the micro-earthquakes caused by the creation of each caving fracture are recorded during mining.
Careful analysis of these recorded signals allows a map of the caving activity to be produced, leading to increased understanding of all aspects of caving.

Salt mine monitoring

Our projects have involved monitoring abandoned salt mines at Northwich and Preesall. The Northwich project involved monitoring of the abandoned mines under the town centre while remediation work was carried out. We have also undertaken work at several gypsum mines.