2017 Volume 70 Pages 1-11
We derived an equation giving a relationship between the average depth of a stratum boundary and the power spectrum of theg gzz component of a gravity gradient tensor. It was found that the relationship was nonlinear to the wave number on a semi-logarithmic scale and that the average depth was estimated to be shallower than the actual one if a conventional linear approximation would be employed. We applied the equation obtained in this study to the gzz component of the gravity gradient tensor observed in the Kuju geothermal area of central Kyushu, Japan, and obtained results that are consistent with the average depth estimated by spectrum analysis of gravity anomaly. On the other hand, we found that the equation could not estimate the average depth of the stratum boundary at the lowest wave number range. In addition, it was shown that the wave number range giving the same average depth as that given by spectrum analysis of gravity anomaly shifts to the higher wave number range, and its range becomes broader.
