[MGI39-P01] 全地球地震活動ダイナミクスー沈み込み帯と海嶺の同期活動
キーワード：相関地震活動、同期活動、沈み込み帯と海嶺
Global Seismicity Dynamics – Synchronicity in Correlated Seismicity of Global Subduction and Ridge Zone.
Mitsuhiro TORIUMI
JAMSTEC
The global seismic data in the USGS catalogue are transformed to the seismic density of unit volume divided along global subduction zone and oceanic ridges between magnitude 4 to 5 from 1990 to 2018. The large data matrixes made by logarithmic transformation are decomposed into coefficient matrixes and orthogonal basis matrix by means of the deterministic PCA (Toriumi 2009, Toriumi 2010, Okada et al., 2017) and probabilistic PCA with LASSO. The results are shown by time series of correlated seismicity rates z1 to z3 for both global subduction zone and oceanic ridge and by intensity spectra of coefficients contributing to the z1 to z3.
The time series of the correlated seismicity rate z1 of the global subduction zone display the step – like increase from 1990 to 2018 with somewhat lowering before and after Tohoku-Oki earthquake but that of the z2 does periodic secular trend having 20 years cycle with Gaussian noise. On the other hand, the time series of the correlated seismicity rate z1 of the global oceanic ridge also appears as step like increase with some degree of undulation. The z2 time series display the weak periodic spike clusters with large noise.
The relationship of z1 between the global subduction zone and the global oceanic ridge clearly shows three clusters and general increase of them with advancing time in their diagram. It seems that three clusters of correlated seismicity rates z1 and z2 of subduction and ridge zones should be due to three times of the globally rapid change of plate motion during recent 30 years. Furthermore, the general trend of these clusters indicates clearly synchronous motion of the subduction and spreading of the plate.
References
Toriumi, M., (2009), Jour. Disaster Res., 4,2,209-213.
Toriumi, M., (2011), COE Lecture Note vol.39, Kyushu Univ., 116-131.
Okada, A., Toriumi, M., and Kaneda, T., 2017, Int. Jour. Geol., 1, 11, 26-34.
Mitsuhiro TORIUMI
JAMSTEC
The global seismic data in the USGS catalogue are transformed to the seismic density of unit volume divided along global subduction zone and oceanic ridges between magnitude 4 to 5 from 1990 to 2018. The large data matrixes made by logarithmic transformation are decomposed into coefficient matrixes and orthogonal basis matrix by means of the deterministic PCA (Toriumi 2009, Toriumi 2010, Okada et al., 2017) and probabilistic PCA with LASSO. The results are shown by time series of correlated seismicity rates z1 to z3 for both global subduction zone and oceanic ridge and by intensity spectra of coefficients contributing to the z1 to z3.
The time series of the correlated seismicity rate z1 of the global subduction zone display the step – like increase from 1990 to 2018 with somewhat lowering before and after Tohoku-Oki earthquake but that of the z2 does periodic secular trend having 20 years cycle with Gaussian noise. On the other hand, the time series of the correlated seismicity rate z1 of the global oceanic ridge also appears as step like increase with some degree of undulation. The z2 time series display the weak periodic spike clusters with large noise.
The relationship of z1 between the global subduction zone and the global oceanic ridge clearly shows three clusters and general increase of them with advancing time in their diagram. It seems that three clusters of correlated seismicity rates z1 and z2 of subduction and ridge zones should be due to three times of the globally rapid change of plate motion during recent 30 years. Furthermore, the general trend of these clusters indicates clearly synchronous motion of the subduction and spreading of the plate.
References
Toriumi, M., (2009), Jour. Disaster Res., 4,2,209-213.
Toriumi, M., (2011), COE Lecture Note vol.39, Kyushu Univ., 116-131.
Okada, A., Toriumi, M., and Kaneda, T., 2017, Int. Jour. Geol., 1, 11, 26-34.