The results of the geostatistical evaluation suggests the fracture system in the BK area is a complex multi-channel structure. Geophysical techniques were chosen for further characterisation of the site as they minimise disturbance to the hydraulic properties of the rock.

Seismic measurements were made using the BGR mini-sonic-probe. This probe uses a piezoelectric transducer as a seismic source and three piezoelectric transducers as receivers (at distances of 10, 20 and 30 cm from the source).

The BGR mini sonic probe. The distance between the receivers is 10 cm

The principal data acquisition system can be seen below. A single excitation point from the source (marked "S" results in the recorded signals at receivers 1, 2 and 3.)

The following figure was obtained from borehole EFP 98.019 the seismic traces for source-receiver distance of 30 cm. Fracture areas can be seen by the break in the pattern. If the rock had no fractures the signal would have minimal distortion throughout the profile as the signal passes through easily. The fractures cause a dampening of the signal as the signal from the transducers is affected by the changes in the rock.