Feasibility analysis of searching for the Slichter triplet in superconducting gravimeter records

Abstract

The search for the elusive Slichter triplet requires elaborate analysis of the elastic-gravitational mode characters and the non-stationary behavior of noisy time-series. A typical question is that it is difficult to characterize the excitations with attenuation by diffusion when their intensity is low compared to noise. Thus the theory for deriving the modes' frequencies is still controversial, and various scholars tried to search for the Slichter triplet in superconducting gravimeter (SG) records, but failed. One of the main causes might be due to the inappropriate use of datasets. We present in this paper synthetic experiments on the selection of record length, sampling rate and number of SG records under the Global Geodynamics Project (GGP) to detect the damped harmonic signals hidden in noises based on the optimal sequence estimation (OSE) method. Moreover, our results show that the existing observation conditions arouse restrictions and it might be impossible to detect the Slichter triplet excited by single excitation source based on Fourier spectrum analysis. Thus we suggest a stacking way of combining several seismic events in the case that the excitation mechanism has so far been unclear.