Quantifying Changes in Time-Lapse TEM Data Due to Temperature-Induced Resistivity Variations

Monitoring studies based on the transient electromagnetic (TEM) method are promising. However, temperature effects are not well understood, compared to monitoring ERT studies. Thus, a detailed study of temperature effects on monitoring TEM data can provide valuable insights for future studies. In this study, nearly daily measurements collected over nearly 24 months with a semi-permanent monitoring TEM system show that temperature-induced changes in subsurface resistivity are reflected in the dB/dt signal and subsequently propagate into the model space. A Pearson correlation analysis between inverted resistivity and air temperature shows a maximum correlation coefficient of 0.92 with a 40-day time-lag. This work demonstrates how monitoring TEM data can be affected by temperature as observed in other geophysical methods. Thus, practitioners should be aware of the possible temperature effects in their data, particularly in conductive environments.