MBAS- Multistation Borehole Geophone from Geotomagraphie
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.
Undertaking downhole and crosshole tomography shear wave inventions with a single 3 component borehole geophone are time consuming and costly. Much of the survey time is spent correctly orientating the borehole geophone or downhole source. As a result shear wave downhole and crosshole investigations for near surface ground investigations have been predominantly specified for large infrastructure projects. The MBAS is designed to increase downhole and crosshole tomography shear wave productivity by offering an array of up to 10 three component stations. With a station interval of 1 or 2m the stiff hose permits the operator to easily control the alignment of every station.
The system incorporates a 24bit A/D offering 256 to 32768Hz sampling and a maximum record length of 4s.