DDS: Dual Downhole System

The Dual Downhole System (DDS) is used to receive P and S-waves in dry and water filled boreholes in order to determine interval velocities. The DDS consists of two stations each equipped with tri-axial sensors. The stations are mechanically connected to each other to ensure the alignment of all horizontal sensors. Both stations are coupled to the borehole wall by a pneumatic clamping system (inflatable bladder). Air is supplied to the DDS through an electro-pneumatic hybrid cable with a Kevlar tension string. A magnetic compass shows azimuthal deviation to North and can be used to get the orientation of the DDS in the borehole. The cable is terminated by a connector to the seismograph.