A microseismic piezofilm sensor

Monitoring seismic activity in mines is an important issue for mine safety. This seismic activity is produced by high stress faults in the vicinity of the mining operations. To estimate the location of a radiating seismic source the acoustic pressure wave travelling through the rock must be recorded at a number of sensors throughout the mine. The arrival time estimates for a seismic event are then used to locate the source. This low-energy seismic activity in mines is typically referred to as microseismic events. This paper focuses on a alternative sensor for recording microseismic activity. This sensor uses piezofilm as the sensing element. Piezofilm is a piezoelectric polymer that generates a charge when it is mechanically deformed. It is a flexible, lightweight, tough plastic film, which is extremely sensitive to any mechanical deformation. The paper describes the sensor, which can be modelled as a second order system. Laboratory results characterizing the sensor are presented. Finally, some in-mine tests comparing the piezofilm sensor with a commercial geophone sensor are presented.