Provides high spatial resolution images of P- and S-wave velocities to delineate geological structures
Seismic tomography provides high-resolution 2D or 3D images of seismic velocities between boreholes. The method is used to delineate geological structures, to map cavities and weak zones and to specify mechanical soil and rock properties.
Geophysicists and engineers apply this method to investigate the foundation and underlying rock of buildings and bridges in order to characterize the subsurface before infrastructure is built and to image time-dependent processes.
P-wave
P-wave tomography is a standard method for high-resolution geological structure exploration between boreholes. P-waves are generated in one borehole and being transmitted to the other. P-wave tomography measurements are easy to analyze due to the easy recognition of the first arriving seismic waves.
Source
SBS42 | P-Wave Source
The borehole source SBS42 generates compressional waves (P) in water filled boreholes. The seismic signals are highly repeatable. Energy released by the IPG5000 discharges through a coaxial cable terminated by two adjacent spark electrodes. The spark discharge vaporizes water by a high-pressure plasma. This generates vapour bubbles which expand and collapse, thereby generating high-frequency seismic waves.
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Receiver
BHC4 | Hydrophone String
The hydrophone string BHC4 is used to receive P-waves in water filled boreholes. The BHC4 consists of a downhole cable containing a Kevlar tension string and a number of moulded hydrophones at pre-defined intervals. Each hydrophone consists of a sensor with a pre-amplification board. The electronic boards are powered from the surface by a bank of rechargeable AA cells. The cable is terminated by a connector to the seismograph.
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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.
Download product sheet.pdf
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S-wave
S-wave tomography links high-resolution borehole geophysics to soil dynamic properties. S-waves need to be generated with different polarization in order to be easily recognized during data processing. Due to its shorter wavelength compared to P-waves the S-wave provides a much higher resolution.
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.
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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.
Download product sheet.pdf
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.
