SEISMIC ACQUISITION IN HOLES
In this type of seismic prospecting, the source and/or geophones are located in a specially prepared hole in the ground. To guarantee high quality data, these holes must comply with the standards indicated in the relevant ASTM standards. Among the most common methods are downhole testing, where the source is on the surface while the sensor is instead made up of a 3D hole geophone (P & S waves) or a hydrophone chain (only P waves in a water-filled hole or drilling fluid). Downhole testing is aimed at determining the profiles of the seismic compression, P, and shear waves, S, with depth. It consists in producing a disturbance on the ground surface by a mechanical source and in measuring the arrival time of the direct waves, P and S, at the various depths within the appropriately prepared hole. This technique is also used for the calculation of Vs30 as an alternative to surface methods (i.e. MASW). Crosshole seismic testing instead involves the measurement of seismic wave velocities between two probing holes, one for the shot (normally carried out with a bore or explosive energiser) and the other for measurement (with a three-dimensional anchored geophone). For each acquisition, the position of the shot and the measurement in the two holes must be the same. In this case, therefore, two coated and well-cemented boreholes must be available, of which the mutual distance to all measurement dimensions is known. Crosshole results are fundamental also to improve seismic tomography surveys.
WHAT YOU NEED for DOWNHOLE survey
instrument
P.A.S.I. GEA24 complete with GEA-PC acquisition software + your laptop / tablet / PC
GEA24 is a compact-sized 24 channel seismograph (can be serialized for a total of 48 ch.) with a 24 bit data acquisition board and USB interface for external PC (not included in the standard supply). Suitable for all applications, GEA-24 is a reliable, affordable solution for all professional uses.
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accessories
GFA borehole 3D geophone (with 50 or 100 m of cable) +
Sledge hammer
Piezoelectric starter
Striking plate
Horizontal wave striking plate
GPS option
software (choice of one) +
INTERSISM
WIN_DOWNHOLE
RAYFRACT – SEISMIC TOMOGRAPHY
WHAT YOU NEED for CROSSHOLE survey - SEISMIC TOMOGRAPHY
instrument
P.A.S.I. GEA24 complete with GEA-PC acquisition software + your laptop / tablet / PC
GEA24 is a compact-sized 24 channel seismograph (can be serialised for a total of 48 chan.) with a 24 bit data acquisition board and USB interface for external PC (not included in the standard supply). Suitable for all applications, GEA-24 is a reliable, affordable solution also for crosshole surveys and seismic tomography.
FIND OUT MORE
REQUEST A QUOTATION
accessories
2x GFA borehole 3D geophone (with 50 or 100 m of cable) +
P/S CHE Crosshole energizer +
GPS option
software +
GEOTOM3D+TOMTIME
RAYFRACT – SEISMIC TOMOGRAPHY