Geoelectric Reference Technique, Efficient Tool to Eliminate External Noise in SIP Data

External noise disturbs measurements carried out with the method of Spectral Induced Polarization (SIP), and lessens its data quality. In densely populated areas the disturbance signals mostly originate from high voltage power lines and the electrical devices supplied by them. However, disturbances (tellurics, lightnings) also appear in remote areas. At frequencies up to 250 kHz, disturbances through VLF and LW transmitters are also be taken into account. Stacking techniques are very time-consuming. We have implemented and tested the novel Geoelectrical Reference Technique, which with reasonable additional hardware costs effectively reduces most noise types without loss of time. External noise is characterized through a high spatial coherence. The signals of disturbance source can be observed in a large area. The Geoelectrical Reference Technique uses this fact by recording the noise at one or more remote locations. In doing so, the technique predicts and eliminates the coherent noise components contained in the SIP records. In order to use the Geoelectric Reference Technique in a wide frequency band, we developed a completely new hardware (SIP-Fuchs-4). Field measurements show that the Geoelectric Reference Technique improves the data quality at medium frequencies by a factor of up to 40.