BGK3/7 Borehole Geophone

The borehole geophone BGK3 is used to receive P- and S-waves in dry or water-filled boreholes. The borehole geophone BGK3 consists of a tri-axial sensor whereas the BGK7 consists of six horizontal sensors, separated by 30° intervals, and one vertical sensor. The geophone is coupled to the borehole wall by a pneumatic clamping system (inflatable bladder). Air is supplied to the BGK3/7 through an electro-pneumatic hybrid cable with a Kevlar tension string. A magnetic compass shows azimuthal deviation to the North and can be used to get the orientation of the geophone in the borehole. The cable is terminated by a connector to the seismograph.