Technical
Aquamap on Rob's Country, CTV
Aqua Tronic Solutions were featured on Rob's Country on CTV whose technology is exclusively available in New Zealand through Aquamap. Part One shows how electroseismic equipment is used to locate groundwater directly. In Part Two of the show this technology taken to an area reputed to be completely dry to show us just how amazing it is.
Aquamap on Rob's Country: Part One Aquamap on Rob's Country: Part Two
The Electro-Seismic Effect
Background
The electro-seismic effect describes the conversion from seismic to electromagnetic (EM) energy. Several mechanisms are likely to generate couplings between seismic and EM energy in the subsurface (Garambois et al. (2002)). The main effects of interest to geophysicists are electrokinetic and piezoelectric phenomena and variations in electrical resistivity.
The macroscopic governing equations were derived from first principals by Pride (1994) which coupled Biot’s theory and Maxwell equations via flux/force transport equations. In this theory the coupling mechanism is explained by electrokinetic effects taking place at pore level.
Wave Behaviour
A seismic wave propagating in a medium can induce an electrical field or cause radiation of an electromagnetic wave. There are two electro-seismic effects that are considered in this report (Oleg et al. (1997)).
The first effect is caused when a seismic wave crosses an interface between two media. When the spherical P-wave crosses the interface, it creates a dipole charge separation due to the imbalance of the streaming currents induced by the seismic wave on opposite sides of the interface. The electrical dipole radiates an EM wave which can be detected by remote antennas as shown in Figure 1.
Figure 1: Seismic wave crossing an interface generating an electromagnetic wave.
The second effect is caused when a seismic head wave travels along an interface between two media. It creates a charge separation across the interface, which induces an electrical field. This electric field moves along the interface with the head wave and can be detected by antennas when the head wave passes underneath as shown in Figure 2.
Figure 2: Head wave travelling along an interface generating an electric field.