The response method applied to the analysis of superconducting gravimeter data

Abstract

The response method, a technique used in ocean tide analysis to separate linear and nonlinear components, is applied to the analysis of superconducting gravimeter data. A response analysis is shown to be capable of resolving small non-tidal signals of a few nanogal amplitude arbitrarily close in frequency to large amplitude tidal signals. A synthetic example, in which a small signal is injected into a spectrally rich tidal signal is used to demonstrate how the method is applied and its advantages compared to a conventional analysis. The technique is also applied to the analysis of degree 3 diurnal and semi-diurnal tides in short records. The degree 3 waves are easily separated and a reasonable ocean loading effect for these waves is recovered, despite the fact the open ocean tide is only a few mm in amplitude. Finally, a response analysis is used to separate gravitational tides from the radiation tides at coincident frequencies in both the diurnal and semi-diurnal bands.