Among the different four‐electrode arrays used in resistivity sounding and profiling, the dipole‐dipole array can provide, in some instances, advantages over the more conventional Schlumberger and Wenner configurations. Interpretation of data from Wenner and Schlumberger methods has been described by Compagnie Générale de Géophysique (1955), Mooney and Wetzel (1956), Zohdy (1964), and many others. The primary reason for using a dipole‐dipole array has been to minimize inductive coupling between the transmitting and receiving dipoles when performing frequency‐domain, induced‐polarization surveys (e.g., Marshall and Madden, 1959). This inductive coupling, as effected by the presence of the earth, produces spurious frequency‐dependent voltages in the measuring circuit. Such spurious voltages are small and only of importance when one wishes to calculate the percentage change in resistivity between two frequencies; they are usually much less than the 5 to 10 percent accuracy sought in most resistivity surveys. For this reason, and because the dipole‐dipole array leads to small measured potentials, it is seldom used in single‐frequency resistivity sounding or profiling. However, we shall demonstrate in this paper the manner in which the dipole‐dipole array may be used effectively for simultaneous sounding and profiling.
Electrical resistivity tomography and time-domain induced polarization field investigations of geothermal areas at Krafla, Iceland: comparison to borehole and laboratory frequency-domain electrical observations