Technical developments (sources & equipment)

The quality of a seismic survey is based upon the seismic source and acquisition technique that is applied to a geological target, as well as the recording conditions. Important points are e.g. strength and repeatability of the source, coupling to the surface, bandwidth and frequency content of the signal. Logistic requirements are also important, such as e.g. manageability in difficult terrains.

A source that especially considers the last aspect, is the seismic impulse source system (SISSY). It can be used where vehicles cannot. Its energy, enough for a survey depth to approximately 500 m, comes from a propellant cartridge of only 8 g. Due to its construction and electrical ignition, it is very safe and can be used without special permission.

Vibratory sources have the advantage of controllable frequency. Whereas vibrators used in the hydrocarbon industry weigh generally much more than 10 t, the hydraulic vibrators developed and realised by LIAG in cooperation with industrial partners for generation of P-waves (MHV 2.7) and S-waves (MHV 4.0) are significantly smaller and have a high frequency signal of 20 – 500 Hz. They can be used for reconnaissance depths from a few tens of meters up to 1 km. For shallower surveys we have constructed electrodynamic vibrators (ELVIS) for P-waves and S-waves. These systems, using a direct current, low tension supply, can be used very flexibly due to their low weight (95 kg).

The last decades have seen a continuous increase in channel count, also in the near surface seismic. At the present, LIAG has a 294 channel modular system. Due to the development of multicomponent seismic, new cable systems have had to be constructed.

In reconnaissance below sealed surfaces, e.g. densely covered with buildings, traffic areas, or large factory floors, is not possible to use traditional spike geophones. Therefore, we have developed land streamers for all components, that can be moved continuously.