Based upon seven superconducting gravimeter （SG） records of 20 000 h length after the 2004 Sumatra earthquake, four methods, namely the ensemble empirical mode decomposition （EEMD）, the multi-station experiment （...Based upon seven superconducting gravimeter （SG） records of 20 000 h length after the 2004 Sumatra earthquake, four methods, namely the ensemble empirical mode decomposition （EEMD）, the multi-station experiment （MSE） technique, the autoregressive （AR） method and the product spec- trum analysis （PSA） method, are chosen jointly together to detect the inner core translational modes （1S1）. After the conventional pretreatment, each of the seven simultaneous residual gravity series is di- vided into five segments with an 80% overlap, and then EEMD is applied to all the 35 residual SG se- ries as a dyadic filter bank to get 35 filtered series. After then, according to different stations and dif- ferent time windows, five new simultaneous gravity datasets are obtained. After using MSE for each of the five new datasets, the AR method is used to demodulate some known harmonic signals from the new sequences that obtained by using MSE, and three demodulated product spectra are obtained. Then, according to two criterions, two clear spectral peaks at periods of 4.548 9±2.3×10^-5 and 3.802 3±3.2×10^-5 h corresponding respectively to the singlets m=-1 and m=＋l are identified from various spectral peaks, and they are close to the predictions of the 1066A model given by Rieutord （2002）, but no spectral peak corresponding to the singlet m=0 is found. We conclude that the selected two peaks might be the ob- served singlets of the Slichter triplet.展开更多
基金supported by the National Natural Science Foundation of China(No.41174011)the National Natural Science Foundation of China(Nos.41128003,41021061,40974015)+2 种基金the National 973 Project of China(No.2013CB733305)the Fundamental Research Funds for the Central Universities(No.2012214020203)the Open Research Fund Program of the Key Laboratory of Geospace Environment and Geodesy,Ministry of Education,China(Nos.12-02-04,12-02-02)
文摘Based upon seven superconducting gravimeter （SG） records of 20 000 h length after the 2004 Sumatra earthquake, four methods, namely the ensemble empirical mode decomposition （EEMD）, the multi-station experiment （MSE） technique, the autoregressive （AR） method and the product spec- trum analysis （PSA） method, are chosen jointly together to detect the inner core translational modes （1S1）. After the conventional pretreatment, each of the seven simultaneous residual gravity series is di- vided into five segments with an 80% overlap, and then EEMD is applied to all the 35 residual SG se- ries as a dyadic filter bank to get 35 filtered series. After then, according to different stations and dif- ferent time windows, five new simultaneous gravity datasets are obtained. After using MSE for each of the five new datasets, the AR method is used to demodulate some known harmonic signals from the new sequences that obtained by using MSE, and three demodulated product spectra are obtained. Then, according to two criterions, two clear spectral peaks at periods of 4.548 9±2.3×10^-5 and 3.802 3±3.2×10^-5 h corresponding respectively to the singlets m=-1 and m=＋l are identified from various spectral peaks, and they are close to the predictions of the 1066A model given by Rieutord （2002）, but no spectral peak corresponding to the singlet m=0 is found. We conclude that the selected two peaks might be the ob- served singlets of the Slichter triplet.
