Based on eight published plate motion models, we separately estimated the net area changes of tectonic plates and the area change of the solid Earth surface over geological time using the Euler vectors of plates with ...Based on eight published plate motion models, we separately estimated the net area changes of tectonic plates and the area change of the solid Earth surface over geological time using the Euler vectors of plates with determined boundaries. Then, under the context of a currently expanding Earth, we inferred the change rate of the Earth’s mean radius from the estimated net area changes. The results show that the total increases and decreases in the areas of different plates cannot be compensated. Specifically, the area of the Northern Hemisphere decreases while that of the Southern Hemisphere increases, but the net area of the solid Earth surface slightly increases in th computing period(0.01 Ma). For the latest NNRMORVEL56 plate motion model, the area of the Southern Hemisphere increases by 7802 km2 while the area of the Northern Hemisphere decreases by 7711 km^2. This indicates a net area increase of 91 km2 in the solid Earth surface corresponding to an expansion rate of 0.06 mm/a for the Earths mean radius.This result coincides with the slow rate of expansion derived from geodetic measurements and geophysical modeling.展开更多
Subduction zones can generally be classified into Mariana type and Chilean type depending on plate ages, plate thicknesses, subduction angles, back-arc deformation patterns, etc. The double seismic zones （DSZs） in s...Subduction zones can generally be classified into Mariana type and Chilean type depending on plate ages, plate thicknesses, subduction angles, back-arc deformation patterns, etc. The double seismic zones （DSZs） in sub- duction zones are mainly divided into type I and type II which, respectively, correspond to the Mariana type and Chilean type in most cases. Seismic anisotropy is an important parameter characterizing the geophysical fea- tures of the lithosphere, including the subduction zones, and can be described by the two parameters of delay time ~t and fast wave polarization direction ~b. We totally col- lected 524 seismic anisotropy data records from 24 DSZs and analyzed the statistical correlations between seismic anisotropy and the related physical parameters of DSZs. Our statistical analysis demonstrated that the fast wave polarization directions are parallel to the trench strike with no more than 30~ for most type I DSZs, while being nearlyperpendicular to the trench strike for type II DSZs. We also calculated roughly linear correlations that the delay time 6t increases with dip angles but decreases with subduction rates. A linear equation was summarized to describe the strong correlation between DSZ＇s subduction angle DSZ and seismic anisotropy in subduction zones. These results suggest that the anisotropic structure of the subducting lithosphere can be described as a possible equivalent crystal similar to the olivine crystal with three mutually orthogonal polarization axes, of which the longest and the second axes are nearly along the trench-perpendicular and trench-parallel directions, respectively.展开更多
A workshop on crustal structure and seismotectonics was held on the Chinese Teacher＇s Day, the September 10th of 2011, in the city Lanzhou, China. Scientists and graduate students from Chinese Academy of Sciences, Ch...A workshop on crustal structure and seismotectonics was held on the Chinese Teacher＇s Day, the September 10th of 2011, in the city Lanzhou, China. Scientists and graduate students from Chinese Academy of Sciences, China Earthquake Administration, Chinese Academy of Geological Sciences, and Japan Agency for Marine-Earth Science and Technology delivered over 20 oral presentations, with topics covering crustal and upper mantle structure, seismic anisotropy, recent earthquakes and seismotectonics,展开更多
基金supported by the National Natural Science Foundation of China(Grant No. 41474086 and 41704080)the Basic Research Project of Institute of Earthquake Forecasting of China Earthquake Administration (Grant No. 2018IES0402)supported by Academia Sinica
文摘Based on eight published plate motion models, we separately estimated the net area changes of tectonic plates and the area change of the solid Earth surface over geological time using the Euler vectors of plates with determined boundaries. Then, under the context of a currently expanding Earth, we inferred the change rate of the Earth’s mean radius from the estimated net area changes. The results show that the total increases and decreases in the areas of different plates cannot be compensated. Specifically, the area of the Northern Hemisphere decreases while that of the Southern Hemisphere increases, but the net area of the solid Earth surface slightly increases in th computing period(0.01 Ma). For the latest NNRMORVEL56 plate motion model, the area of the Southern Hemisphere increases by 7802 km2 while the area of the Northern Hemisphere decreases by 7711 km^2. This indicates a net area increase of 91 km2 in the solid Earth surface corresponding to an expansion rate of 0.06 mm/a for the Earths mean radius.This result coincides with the slow rate of expansion derived from geodetic measurements and geophysical modeling.
基金supported by the National Natural Science Foundation of China(41174084 and41474086)the CAS/CAFEA International Partnership Program for creative research teams(KZZD-EW-TZ-19)
文摘Subduction zones can generally be classified into Mariana type and Chilean type depending on plate ages, plate thicknesses, subduction angles, back-arc deformation patterns, etc. The double seismic zones （DSZs） in sub- duction zones are mainly divided into type I and type II which, respectively, correspond to the Mariana type and Chilean type in most cases. Seismic anisotropy is an important parameter characterizing the geophysical fea- tures of the lithosphere, including the subduction zones, and can be described by the two parameters of delay time ~t and fast wave polarization direction ~b. We totally col- lected 524 seismic anisotropy data records from 24 DSZs and analyzed the statistical correlations between seismic anisotropy and the related physical parameters of DSZs. Our statistical analysis demonstrated that the fast wave polarization directions are parallel to the trench strike with no more than 30~ for most type I DSZs, while being nearlyperpendicular to the trench strike for type II DSZs. We also calculated roughly linear correlations that the delay time 6t increases with dip angles but decreases with subduction rates. A linear equation was summarized to describe the strong correlation between DSZ＇s subduction angle DSZ and seismic anisotropy in subduction zones. These results suggest that the anisotropic structure of the subducting lithosphere can be described as a possible equivalent crystal similar to the olivine crystal with three mutually orthogonal polarization axes, of which the longest and the second axes are nearly along the trench-perpendicular and trench-parallel directions, respectively.
基金support by basic research project of Institute of Earthquake Science,China Earthquake Administration(No.2011IESLZ05 and No.2009-11&21)
文摘A workshop on crustal structure and seismotectonics was held on the Chinese Teacher＇s Day, the September 10th of 2011, in the city Lanzhou, China. Scientists and graduate students from Chinese Academy of Sciences, China Earthquake Administration, Chinese Academy of Geological Sciences, and Japan Agency for Marine-Earth Science and Technology delivered over 20 oral presentations, with topics covering crustal and upper mantle structure, seismic anisotropy, recent earthquakes and seismotectonics,
