Tidal modulation of temperature oscillations monitored in borehole Yaxcopoil-1 (Yucatلn, Mexico)

For better understanding of temperature state in the subsurface, temperature-depth logs can be suitably completed by high-resolution long-run temperature-time monitoring at selected depths. The results of temperature monitoring at three depth levels in borehole Yaxcopoil-1, Chicxulub impact structure, Mexico (April/May 2006) proved that even when a borehole is in “fully” stabilized conditions, temperature may exhibit certain unrest resembling irregular oscillations in the order of hundredths or (in the extreme case) even first tenths of degree. Two novel methods for detection of the weak fingerprints of stable periodic components in long noisy records, namely the RQI (Recurrence Quantification Interval) analysis and the HiCum (Histograms Cumulation) were used to isolate the constituents with tidal periodicities from temperature oscillations measured in borehole Yaxcopoil-1. Both analyses revealed that temperature series contain perceptible tidal component. The field data were correlated with the simulated synthetic tides. The comparison of staked HiCum records for the theoretical gravity tide and monitored temperature shows significant positive linear correlation between both variables. There is a small lag between two signals corresponding to ~ 25 min phase difference.