Data Quality Quantification for Time Domain IP Data Acquired along a Planned Tunnel near Oslo, Norway

Tests were done measuring resistivity and time domain induced polarisation using standard multi-core cable spreads and a special layout with separate cable spreads for transmitting current and measuring potentials. For both types of cables spreads both normal and reciprocal measurements were done in order to estimate the measurement errors. The tests were done along a planned tunnel stretch outside Olso in Norway. The electrode contact was variable with resistances in the range 0.6 - 25 kΩ. The results gave low
median error levels for both types of cable spreads, but the single cable spread showed a significantly larger variation with more scatter in the IP data. Data for both types of spreads gave models that are consistent and appear to delineate the complex geology in a useful way. It is concluded that the single cable spread gives surprisingly good IP data considering the large layouts at this site, which is adequate for inversion of the integrated full decay. If on the other hand the data were to be used for spectral IP inversion of the decay curves for recovering the Cole-Cole parameters the extra effort of measuring with separated cable spreads would probably be well motivated.