Tomography equipment

Source

BIS-SH | S-Wave Source

The borehole source BIS-SH generates horizontally polarized shear waves (SH) and compressional waves (P). The seismic signals are highly repeatable. The source works in dry or water filled boreholes and can be used in vertical or horizontal boreholes.

Energy released by the IPG5000 discharges through a system of electromagnetical coils adjacent to a copper plate. If the plate is rejected a mechanical impact to the borehole wall is generated. The borehole source is coupled to the borehole wall by a pneumatic clamping system (inflatable bladder). The orientation of the source is controlled from surface by a torsionally stiff hose.

The borehole source BIS-SV generates vertically polarized shear waves (SV) in dry or water filled boreholes. The BIS-SV source can be used with the impulse generators IPG800 or IPG5000. The coupling to the borehole wall is ensured by a pneumatic clamping system (infatable bladder). The source is designed for seismic crosshole applications. No special alignment of the source is required in the borehole. A switch box is provided to select one of the two SV shot directions „UP“ and „Down“ which improves the practicability of the S-wave source.

In combination with the P-wave sparker source (SBS42) and the SH-wave source (BIS-SH) P-, SH- and SV-waves can be measured and used for a comprehensive characterization of soil mechanical parameters. SV velocities together with SH velocities can be used to evaluate the soil stress history. Together with P-waves, a joint inversion can be done to analyse the anisotropic properties of soils.

Receiver

MBAS | Multistation Borehole Geophone

The Multistation Borehole Acquisition System (MBAS) is a digital three-component geophone string used to receive P- and S-waves in dry or water filled boreholes. Up to ten individual stations with tri-axial sensors can be connected. The stations are aligned to ensure that all horizontal sensors are oriented in same direction. The system can be oriented from the surface by a torsionally stiff hose. Each station is clamped to the borehole wall by two pneumatic cylinders. An external trigger can be plugged into the USB interface on surface which is connected to a laptop. The operation is entirely controlled by the acquisition software. A separate seismograph is not required.

Power supply

IPG5000 | Impulse Generator

The Impulse Generator IPG5000 (formerly named IPG1005) is the high voltage supply to the seismic borehole sources BIS-SH and SBS42. The energy is stored in a large capacitor bank which discharges through a mechanical switch.

The IPG5000 is controlled by a Remote Control Unit (RCU). The RCU allows the user to start the seismic survey by a single or continuous shot release. The repetition rate is freely selectable under continuous operation. The RCU is connected to the seismograph to send an accurate trigger signal.