The data of Bouguer gravity and topography are inverted to obtain the crust thickness of China. In order to reduce the effect of regional non-isostasy we corrected the reference Moho depth in the inversion with region...The data of Bouguer gravity and topography are inverted to obtain the crust thickness of China. In order to reduce the effect of regional non-isostasy we corrected the reference Moho depth in the inversion with regional topography relief, and performed multiple iterations to make the result more reliable. The obtained crust thickness of China is plotted on a map in cells of l°×1°. Then we analyzed the correlation between the Bouguer gravity anomaly and fluctuation of the Moho depth. A good linear correlation is found, with a correlation coefficient of -0.993. Different correlation coefficients, 0.96 and 0.91, are found for the data in land and ocean region, respectively. The correlation result also shows that the boundary between land and ocean is generally along the bathymetric line of -800 m. In order to examine the influence of the Earth＇s curvature on the calculated result, we tried two inversion models： the inversion for the whole region and the inversion for 4 sub-regions. The difference in the crust thickness deduced from the two models is less than 5 km. Possible explanation for the difference is discussed. After comparing our result with that of other studies, we suggest that with our method the Bouguer gravity and the topography data can be independently inverted to obtain the crust thickness of China and its adjacency.展开更多
By using the teleseismic receiver function method, this paper analyzes the crustal thickness and Vp/Vs ratios beneath the 4 National seismic stations （KMI, TNC, CD2 and PZH） in the Sichuan-Yunnan area. This study gi...By using the teleseismic receiver function method, this paper analyzes the crustal thickness and Vp/Vs ratios beneath the 4 National seismic stations （KMI, TNC, CD2 and PZH） in the Sichuan-Yunnan area. This study gives the variance of Moho depths and velocity ratios of the 4 stations in different directions. The results show that the Moho depth beneath the Kunming station is around 50km, and the vdocity ratio varies between 1.62 and 1.69. The thickness of crust and the velocity ratio do not change much with the direction. The crust beneath Tengchong station shows clear directivity, being 40.7km thick in the northeast and 49.7km thick in the southeast. The difference of the Vp/Vs values is remarkable between the two directions, reaching 0.2. The Chengdu station also has shallow Moho, about 40km, but is 8km deeper in the northeast and southwest and the vdocity ratio has a change of 0.13 between the two directions. The crust beneath the Panzhihua station is stable. In all directions, the Moho depth is around 60km and the Vp/Vs ratio doesn＇t change significantly.展开更多
We must persevere to drill through the intact ocean crust to fully address fundamental questions towards completion of the plate tectonics theory.The primary questions include:what is the ocean crust made up of,how th...We must persevere to drill through the intact ocean crust to fully address fundamental questions towards completion of the plate tectonics theory.The primary questions include:what is the ocean crust made up of,how thick is it and what is the petrological nature of the crust-mantle boundary(i.e.,Mohorovičićdiscontinuity or Moho)?These questions may sound naive because they are widely believed to be well-understood facts,but they are not.Correctly,our current knowledge remains incomplete,and some popular misperceptions come from interpretations based on convenient assumptions.One assumption is that the ocean crust inferred from seismic data is of magmatic origin.Testing this assumption is a principal motivation of Project Mohole(1957-1966),attempting to drill intact ocean crust across the Moho into the mantle.Project Mohole failed because of its high cost,engineering challenges and insufficient tries,but the technologies developed made subsequent ocean drilling successful.However,answers to the original questions remain unsatisfactory.For example,seismic crust interpreted to be of magmatic origin is shown to have globally uniform thickness of 6.0±1.0 km,but crust with such thickness at many slow-spreading ridge segments is dominated by serpentinized mantle peridotites exposed on seafloors.Therefore,the popular view on ocean ridge magmatism must be re-examined,which needs intact ocean crust drilling into the mantle.Drilling at geologically simple sites in the fast-spreading Pacific seafloor is most promising.The US-led D/V JOIDES Resolution that has well served the scientific ocean drilling since 1985 is to retire by the end of 2024,but timely the Chinese geoscience community wishes to continue this international endeavor using the purpose-built D/V Meng Xiang to be in service in 2025.The international community is to gather in November 24-27,2024,Guangzhou,China,to discuss strategies on where and how to successfully drill intact ocean crust across the Moho in coming years.展开更多
文摘The data of Bouguer gravity and topography are inverted to obtain the crust thickness of China. In order to reduce the effect of regional non-isostasy we corrected the reference Moho depth in the inversion with regional topography relief, and performed multiple iterations to make the result more reliable. The obtained crust thickness of China is plotted on a map in cells of l°×1°. Then we analyzed the correlation between the Bouguer gravity anomaly and fluctuation of the Moho depth. A good linear correlation is found, with a correlation coefficient of -0.993. Different correlation coefficients, 0.96 and 0.91, are found for the data in land and ocean region, respectively. The correlation result also shows that the boundary between land and ocean is generally along the bathymetric line of -800 m. In order to examine the influence of the Earth＇s curvature on the calculated result, we tried two inversion models： the inversion for the whole region and the inversion for 4 sub-regions. The difference in the crust thickness deduced from the two models is less than 5 km. Possible explanation for the difference is discussed. After comparing our result with that of other studies, we suggest that with our method the Bouguer gravity and the topography data can be independently inverted to obtain the crust thickness of China and its adjacency.
文摘By using the teleseismic receiver function method, this paper analyzes the crustal thickness and Vp/Vs ratios beneath the 4 National seismic stations （KMI, TNC, CD2 and PZH） in the Sichuan-Yunnan area. This study gives the variance of Moho depths and velocity ratios of the 4 stations in different directions. The results show that the Moho depth beneath the Kunming station is around 50km, and the vdocity ratio varies between 1.62 and 1.69. The thickness of crust and the velocity ratio do not change much with the direction. The crust beneath Tengchong station shows clear directivity, being 40.7km thick in the northeast and 49.7km thick in the southeast. The difference of the Vp/Vs values is remarkable between the two directions, reaching 0.2. The Chengdu station also has shallow Moho, about 40km, but is 8km deeper in the northeast and southwest and the vdocity ratio has a change of 0.13 between the two directions. The crust beneath the Panzhihua station is stable. In all directions, the Moho depth is around 60km and the Vp/Vs ratio doesn＇t change significantly.
基金supported by grants from NSFC(91958215)Shandong Basic Research Office(WSR2023018)the Ministry of Education 111 Project(B18048).
文摘We must persevere to drill through the intact ocean crust to fully address fundamental questions towards completion of the plate tectonics theory.The primary questions include:what is the ocean crust made up of,how thick is it and what is the petrological nature of the crust-mantle boundary(i.e.,Mohorovičićdiscontinuity or Moho)?These questions may sound naive because they are widely believed to be well-understood facts,but they are not.Correctly,our current knowledge remains incomplete,and some popular misperceptions come from interpretations based on convenient assumptions.One assumption is that the ocean crust inferred from seismic data is of magmatic origin.Testing this assumption is a principal motivation of Project Mohole(1957-1966),attempting to drill intact ocean crust across the Moho into the mantle.Project Mohole failed because of its high cost,engineering challenges and insufficient tries,but the technologies developed made subsequent ocean drilling successful.However,answers to the original questions remain unsatisfactory.For example,seismic crust interpreted to be of magmatic origin is shown to have globally uniform thickness of 6.0±1.0 km,but crust with such thickness at many slow-spreading ridge segments is dominated by serpentinized mantle peridotites exposed on seafloors.Therefore,the popular view on ocean ridge magmatism must be re-examined,which needs intact ocean crust drilling into the mantle.Drilling at geologically simple sites in the fast-spreading Pacific seafloor is most promising.The US-led D/V JOIDES Resolution that has well served the scientific ocean drilling since 1985 is to retire by the end of 2024,but timely the Chinese geoscience community wishes to continue this international endeavor using the purpose-built D/V Meng Xiang to be in service in 2025.The international community is to gather in November 24-27,2024,Guangzhou,China,to discuss strategies on where and how to successfully drill intact ocean crust across the Moho in coming years.
