Doubling the Spectrum of Time-domain Induced Polarization by Harmonic De-noising, Drift/Spike Removal and Tapered Gating

The extraction of spectral information in the inversion process of time-domain (TD) induced polarization (IP) data is changing the use of the TDIP method. Data interpretation is evolving from a qualitative description of the subsurface, able only to discriminate the presence of contrasts in chargeability parameters, towards a quantitative analysis of the investigated media, which allows for detailed soil- and rock-type characterization. Two major limitations restrict the extraction of the spectral information of TDIP data in the field: i) the difficulty of acquiring reliable early-time measurements, and ii) the self-potential drift in the measured potentials distorting the shape of the late time. For measuring at early times, we developed a new method for removing harmonic noise from the data. Furthermore, a new scheme for spike removal was developed and tapered windows are used in the data gating. For measuring at late times, we developed a drift-removal scheme that model the polarization effect and allows for preserving the shape of the IP responses at late times. Overall, the removal of harmonic noise, spikes, self-potential drift, tapered windowing, and the uncertainty estimation allows for doubling the usable range of TDIP data to almost four decades in time.