March/April 2009

For the love of terra firma

A Canadian company delivers hi-tech, integrated solutions to keep mine management on firm ground

By M. Kerawala

Diagrammatic representation of a typical ESG system installed at a mine

There is a deep, instinctive value accorded to the simple act of standing on firm ground. Perhaps because we derive such comfort from terra firma, human beings have been fascinated and terrified by the prospect of the ground beneath their feet being shaken. As far back as AD 132, the Chinese scientist, Chang Heng, invented an ingenious device to record and locate earthquakes. Comprised of a pendulum and metallic dragons and frogs, Heng’s contraption was beautiful and somewhat effective, but largely imprecise.

In the ensuing centuries, seismometry has come a long way. What has remained unchanged is our need to know when and where the ground will not be firm. Nowhere is this need more acute than in the mining industry, tied to the ground as its fortunes are.

Addressing this requirement is the core purpose of Engineering Seismology Group (ESG) Canada Inc. a Canadian company established in 1993 that provides passive seismic monitoring systems to the resources and geotechnical industries.

A one-stop shop

Seismic monitoring systems are not rare. Jamie Alexander, ESG’s director of North American mining, estimates that about 80 per cent of Canada’s deep mines have them, with greater concentrations in Sudbury and Val-d’Or. ESG microseismic instrumentation has been installed at over 300 sites worldwide. The state-of-the-art systems have ISO 9001:2000 and MSHA Intrinsically Safe certification.

ESG was born of a decade

of intensive industry-sponsored research into seismic hardware, software and interpretative processes. Employing top-flight seismologists, software professionals, geophysicists and technicians, the company remains true to its roots. ESG’s active research and development department seeks to improve products and develop new functionalities making the detection and recording of seismic-type ­activity more accurate and useful.

Better with age

A typical ESG system is made up of a series of finely tuned sensors distributed across strategic underground and surface locations. These are connected by copper cables to ESG Paladin seismic receivers that record and process the sensor data and transmit them by Ethernet cable to surface stations for archival or analysis. Other surface units generate geographic information system (GIS) and timing data, permitting every recorded event to be located precisely in space and time.

The entire system is set up, as Alexander put it metaphorically, “to make a video recording of seismic activity, instead of just taking a snapshot.” Continuous, real-time recording means that no seismic activity, however minute or fleeting, goes unnoticed. “Ethernet connectivity uploads the data to a web-like system, where you can log in remotely or at the surface,” Alexander added.

“Many mines put the ESG system into new developments, so that they can get background-level data on what they can expect seismologically,” Alexander explained. “Every mine will generate some seismic activity. It’s pretty normal. What you need to do is find out what’s not normal.”

It is in distinguishing normal seismic events from concerning ones that the ESG system ages really well. Continuously recording and archiving seismic activity, the system builds up a fund of high-definition data on the site with the passage of time. Voluminous archival data make it easier for analysts to interpret current data more meaningfully and integrate the information into decision-making processes more usefully.

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