Least squares self-coherence for sub-nGal signal detection in the superconducting gravimeter records |
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| Institution: | 1. State Key Laboratory of Geodesy and Earth''s Dynamics, Institute of Geodesy and Geophsics, Chinese Academy of Sciences, Wuhan 430077, China;2. University of Chinese Academy of Sciences, Beijing 100049, China;1. Institute of Seismology, China Earthquake Administration, Wuhan 430071, China;2. Earthquake Research Institute, The University of Tokyo, Tokyo 1130032, Japan;3. State Key Laboratory of Geodesy and Earth''s Dynamics, Institute of Geodesy & Geophysics, Chinese Academy of Sciences, Wuhan 430077, China |
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| Abstract: | In this paper, we use superconducting gravimeter (SG) data recorded at three stations of the global geodynamics project (GGP) network, with good geographical distribution, to search for possible significant peaks in the gravity spectrum that are in the assumed period range of the Slichter triplet. Seven-year long series from Cantley (Canada), and four-year long series from both Canberra (Australia) and Moxa (Germany) stations are used. First, a solid Earth and ocean tide model is subtracted from the data, followed by a local atmospheric pressure correction based on a frequency-, and location-dependent admittance estimated by the least squares response method. Subsequently, the residual series are filtered with a Parzen-based bandpass filter with a passband (12 h–78 s). A sub-nGal detection level is confirmed by injecting an artificial sine wave of different amplitudes. The Least Squares Self-Coherency spectrum shows the existence of many apparently statistically significant peaks at the 95% confidence level in the band (3–8 h). Although a few peaks are close to the claimed Slichter periods in previous research, the large number of candidate peaks may be related to other mechanisms such as global pressure variations, or hydrology. |
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