TY - JOUR
T1 - Measuring time-domain spectral induced polarization in the on-time
T2 - Decreasing acquisition time and increasing signal-to-noise ratio
AU - Olsson, Per Ivar
AU - Dahlin, Torleif
AU - Fiandaca, Gianluca
AU - Auken, Esben
N1 - Publisher Copyright:
© 2015 Elsevier B.V.
PY - 2015/12/1
Y1 - 2015/12/1
N2 - Combined resistivity and time-domain direct current induced polarization (DCIP) measurements are traditionally carried out with a 50% duty cycle current waveform, taking the resistivity measurements during the on-time and the IP measurements during the off-time. One drawback with this method is that only half of the acquisition time is available for resistivity and IP measurements, respectively. In this paper, this limitation is solved by using a current injection with 100% duty cycle and also taking the IP measurements in the on-time. With numerical modelling of current waveforms with 50% and 100% duty cycles we show that the waveforms have comparable sensitivity for the spectral Cole-Cole parameters and that signal level is increased up to a factor of 2 if the 100% duty cycle waveform is used. The inversion of field data acquired with both waveforms confirms the modelling results and shows that it is possible to retrieve similar inversion models with either of the waveforms when inverting for the spectral Cole-Cole parameters with the waveform of the injected current included in the forward computations. Consequently, our results show that on-time measurements of IP can reduce the acquisition time by up to 50% and increase the signal-to-noise ratio by up to 100% almost without information loss. Our findings can contribute and have a large impact for DCIP surveys in general and especially for surveys where time and reliable data quality are important factors. Specifically, the findings are of value for DCIP surveys conducted in urban areas where anthropogenic noise is an issue and the heterogeneous subsurface demands time-consuming 3D acquisitions.
AB - Combined resistivity and time-domain direct current induced polarization (DCIP) measurements are traditionally carried out with a 50% duty cycle current waveform, taking the resistivity measurements during the on-time and the IP measurements during the off-time. One drawback with this method is that only half of the acquisition time is available for resistivity and IP measurements, respectively. In this paper, this limitation is solved by using a current injection with 100% duty cycle and also taking the IP measurements in the on-time. With numerical modelling of current waveforms with 50% and 100% duty cycles we show that the waveforms have comparable sensitivity for the spectral Cole-Cole parameters and that signal level is increased up to a factor of 2 if the 100% duty cycle waveform is used. The inversion of field data acquired with both waveforms confirms the modelling results and shows that it is possible to retrieve similar inversion models with either of the waveforms when inverting for the spectral Cole-Cole parameters with the waveform of the injected current included in the forward computations. Consequently, our results show that on-time measurements of IP can reduce the acquisition time by up to 50% and increase the signal-to-noise ratio by up to 100% almost without information loss. Our findings can contribute and have a large impact for DCIP surveys in general and especially for surveys where time and reliable data quality are important factors. Specifically, the findings are of value for DCIP surveys conducted in urban areas where anthropogenic noise is an issue and the heterogeneous subsurface demands time-consuming 3D acquisitions.
KW - Cole-Cole
KW - Duty cycle
KW - Induced polarization
KW - Signal-to-noise ratio
KW - SNR
KW - Spectral
KW - Waveform
UR - http://www.scopus.com/inward/record.url?scp=84947866498&partnerID=8YFLogxK
U2 - 10.1016/j.jappgeo.2015.08.009
DO - 10.1016/j.jappgeo.2015.08.009
M3 - Article
AN - SCOPUS:84947866498
SN - 0926-9851
VL - 123
SP - 316
EP - 321
JO - Journal of Applied Geophysics
JF - Journal of Applied Geophysics
ER -