By Kari Williamson

The sondes will monitor seismic activity during the opening of the natural fractures in the rock at the geothermal site, which is done by injecting water.

The sondes, built and designed by DJB Instruments, can be deployed to depths of 400 m and do not need a clamping mechanism. Furthermore, the small diameter enables them to be deployed at smaller diameter boreholes.

Large accelerometers and low noise amplifiers give a high output, DJB Instruments says.

The Eden Project's geothermal development will consist of two boreholes drilled 4-5 km into the granite where temperatures reach 180-190°C.