Since the discovery of oceanic manganese nodules during the expedition of the British ocean-going ship Challenger from 1872 to 1876, research and development for seabed manganese nodules have never ceased owing to the...Since the discovery of oceanic manganese nodules during the expedition of the British ocean-going ship Challenger from 1872 to 1876, research and development for seabed manganese nodules have never ceased owing to the huge economic inducements. Manganese nodules are the black or dark brown, spherical or massive Mn-bearing ores, deposits of which are found on the sea bottom. The nodules are a mixture of silicate and insoluble potassium permanganates （also with sub-Ti, Fe and Na permanganates） that contain more than 30 kinds of metallic elements, among which those of greatest economic interest are Mn （27-30%）, Ni（1.25-1.5%）, Cu（1- 1.4%）, Co（0.2- 0.25 %）, Fe, Si, and AI, with minor amounts of Ca, Na, K, Ti, B, H and O.展开更多
On 21 May 2021(UTC),an MW 7.4 earthquake jolted the east Bayan Har block in the Tibetan Plateau.The earthquake received widespread attention as it is the largest event in the Tibetan Plateau and its surroundings since...On 21 May 2021(UTC),an MW 7.4 earthquake jolted the east Bayan Har block in the Tibetan Plateau.The earthquake received widespread attention as it is the largest event in the Tibetan Plateau and its surroundings since the 2008 Wenchuan earthquake,and especially in proximity to the seismic gaps on the east Kunlun fault.Here we use satellite interferometric synthetic aperture radar data and subpixel offset observations along the range directions to characterize the coseismic deformation of the earthquake.Range offset displacements depict clear surface ruptures with a total length of~170 km involving two possible activated fault segments in the earthquake.Coseismic modeling results indicate that the earthquake was dominated by left-lateral strike-slip motions of up to 7 m within the top 12 km of the crust.The well-resolved slip variations are characterized by five major slip patches along strike and 64%of shallow slip deficit,suggesting a young seismogenic structure.Spatial-temporal changes of the postseismic deformation are mapped from early 6-day and 24-day InSAR observations,and are well explained by time-dependent afterslip models.Analysis of Global Navigation Satellite System(GNSS)velocity profiles and strain rates suggests that the eastward extrusion of plateau is diffusely distributed across the east Bayan Har block,but exhibits significant lateral heterogeneities,as evidenced by magnetotelluric observations.The block-wide distributed deformation of the east Bayan Har block along with the significant co-and post-seismic stress loadings from the Madoi earthquake imply high seismic risks along regional faults,especially the Tuosuo Lake and Maqên-Maqu segments of the Kunlun fault that are known as seismic gaps.展开更多
为探究中国铜期货市场价格波动的变化规律并以此预测其风险值,以沪铜期货高频价格数据为样本,综合考虑其收益率波动的聚集性、偏峰厚尾性与长记忆性,将广义已实现测度引入偏t分布假设下的Realized GARCH模型与拓展的Realized HAR GARCH...为探究中国铜期货市场价格波动的变化规律并以此预测其风险值,以沪铜期货高频价格数据为样本,综合考虑其收益率波动的聚集性、偏峰厚尾性与长记忆性,将广义已实现测度引入偏t分布假设下的Realized GARCH模型与拓展的Realized HAR GARCH模型中,并通过样本内拟合与样本外滚动预测,结合似然函数、VaR后验测试与损失函数MCS检验法综合比较了采用不同已实现测度的Realized GARCH以及Realized HAR GARCH模型在沪铜期货收益波动率估计和VaR预测上的效果。实证结果显示:对于沪铜期货市场而言,无论是波动率估计还是风险预测,广义已实现测度的引入显著地提升了Realized GARCH与Realized HAR GARCH模型的拟合效果与预测能力,其中基于日内损失RMAD与RES测度下的Realized HAR GARCH模型分别拥有最优的估计与预测表现。展开更多
Little attention had been paid to the intracontinental strike-slip faults of the Tibetan Plateau. Since the discovery of the Longriba fault using re-measured GPS data in 2003, an increasing amount of attention has bee...Little attention had been paid to the intracontinental strike-slip faults of the Tibetan Plateau. Since the discovery of the Longriba fault using re-measured GPS data in 2003, an increasing amount of attention has been paid to this neglected fault. The local relief and transverse swath profile show that the Longriba fault is the boundary line that separates the high and flat tomography of the Tibet plateau from the high and precipitous tomography of Orogen. In addition, GPS data shows that the Longriba fault is the boundary line where the migratory direction of the Bayan Har block changed from eastward to southeastward. The GPS data shows that the Longriba fault is the boundary fault of the sub-blocks of the eastern Bayan Har block. We built three-dimensional models containing the Longriba fault and the middle segment of the Longmenshan fault, across the Bayan Har block and the Sichuan Basin. A nonlinear finite element method was used to simulate the fault behavior and the block deformation of the Eastern Tibetan Plateau. The results show that the low resistivity and low velocity layer acts as a detachment layer, which causes the overlying blocks to move southeastward. The detachment layer also controls the vertical and horizontal deformation of the rigid Bayan Har block and leads to accumulation strain on the edge of the layer where the Longmenshan thrust is located. After a sufficient amount of strain has been accumulated on the Longmenshan fault, a large earthquake occurs, such as the 2008 Wenchuan earthquake. The strike slip activity of the Longriba fault, which is above the low resistivity and low velocity layer, partitions the lateral displacements of the Bayan Har block and adjusts the direction of motion of the Bayan Har block, from the eastward moving Ahba sub-block in the west to southeastward moving Longmenshan sub-block in the east. Four models with different depths to the Longriba fault were constructed： （1） a shallow fault with a depth of only 4 km, （2） a deeper fault that is half as deep 展开更多
Three regions can easily be identified in the study area according to the Middle Permian palaeobiogeographic distribution of biota, they are the southern slope of East Kunlun, A’nyêmaqên and Bayan Har. Biot...Three regions can easily be identified in the study area according to the Middle Permian palaeobiogeographic distribution of biota, they are the southern slope of East Kunlun, A’nyêmaqên and Bayan Har. Biotic constitution and ecology in the southern slope of East Kunlun and Bayan Har are very similar. Both the diversity and abundance of organisms in these two areas are very high and reefs are widely developed. However, biotic diversity and abundance in A’nyêmaqên which is between the above two areas are obviously low. Differentiation of palaeo- biogeographic distribution in these areas should be due to the baring of A’nyêmaqên ocean in the time of Middle Permian. Middle Permian radiolarian chert and thick abyssal red ooze are widely spread in A’nyêmaqên, implying that the A’nyêmaqên ocean had a great scale in size. Vast scale of deep ocean basin became an impassable gulf for some of the benthos, and as a result, only part of the organisms could have the chance to get to the isolated islands situated in ocean basin. Small living space and hard conditions in the islands further limited the abundance and diversity of biota. Tectonic background reflected by the geochemical study of basalt in the three areas is coupling well enough with the palaeobiogeographic division.展开更多
基于高频数据视角,文章提出时变参数(TV)Realized HAR GARCH混合预测模型,同时考虑资产波动率的聚集性、长记忆以及由测量误差引起的参数衰减偏差效应.进一步,为充分利用价格信息并提升估计效率,本文基于日内“OHLC”数据构建赋权修正...基于高频数据视角,文章提出时变参数(TV)Realized HAR GARCH混合预测模型,同时考虑资产波动率的聚集性、长记忆以及由测量误差引起的参数衰减偏差效应.进一步,为充分利用价格信息并提升估计效率,本文基于日内“OHLC”数据构建赋权修正已实现信息波动率(WRIV),并将其用于驱动条件方差的动态变化.在偏t分布假设下,以沪深300指数为样本探究中国股票市场的波动性规律,并在实证中评估所提模型在收益率拟合、波动率预测以及风险度量上的能力.结果显示:中国股票市场的收益波动存在明显的异质性与长记忆特征,TV-Realized HAR GARCH能够充分捕捉指数波动率的动态变化,在样本内拟合效果和样本外波动率与风险预测准确性上均能显现出优势,且WRIV测度的引入能显著提升模型的预测精度,凸显出日内高频数据信息的充分利用对于波动率刻画与风险测度的重要性,综合而言,TV-Realized HAR GARCH(WRIV)模型具有最优的整体实证表现.展开更多
文摘Since the discovery of oceanic manganese nodules during the expedition of the British ocean-going ship Challenger from 1872 to 1876, research and development for seabed manganese nodules have never ceased owing to the huge economic inducements. Manganese nodules are the black or dark brown, spherical or massive Mn-bearing ores, deposits of which are found on the sea bottom. The nodules are a mixture of silicate and insoluble potassium permanganates （also with sub-Ti, Fe and Na permanganates） that contain more than 30 kinds of metallic elements, among which those of greatest economic interest are Mn （27-30%）, Ni（1.25-1.5%）, Cu（1- 1.4%）, Co（0.2- 0.25 %）, Fe, Si, and AI, with minor amounts of Ca, Na, K, Ti, B, H and O.
基金supported by the Natural Science Foundation of Jiangsu Province(Grant No.SBK2020043202)by Key Laboratory of Geospace Environment and Geodesy,Ministry of Education,Wuhan University(No.19-01-08).
文摘On 21 May 2021(UTC),an MW 7.4 earthquake jolted the east Bayan Har block in the Tibetan Plateau.The earthquake received widespread attention as it is the largest event in the Tibetan Plateau and its surroundings since the 2008 Wenchuan earthquake,and especially in proximity to the seismic gaps on the east Kunlun fault.Here we use satellite interferometric synthetic aperture radar data and subpixel offset observations along the range directions to characterize the coseismic deformation of the earthquake.Range offset displacements depict clear surface ruptures with a total length of~170 km involving two possible activated fault segments in the earthquake.Coseismic modeling results indicate that the earthquake was dominated by left-lateral strike-slip motions of up to 7 m within the top 12 km of the crust.The well-resolved slip variations are characterized by five major slip patches along strike and 64%of shallow slip deficit,suggesting a young seismogenic structure.Spatial-temporal changes of the postseismic deformation are mapped from early 6-day and 24-day InSAR observations,and are well explained by time-dependent afterslip models.Analysis of Global Navigation Satellite System(GNSS)velocity profiles and strain rates suggests that the eastward extrusion of plateau is diffusely distributed across the east Bayan Har block,but exhibits significant lateral heterogeneities,as evidenced by magnetotelluric observations.The block-wide distributed deformation of the east Bayan Har block along with the significant co-and post-seismic stress loadings from the Madoi earthquake imply high seismic risks along regional faults,especially the Tuosuo Lake and Maqên-Maqu segments of the Kunlun fault that are known as seismic gaps.
文摘为探究中国铜期货市场价格波动的变化规律并以此预测其风险值,以沪铜期货高频价格数据为样本,综合考虑其收益率波动的聚集性、偏峰厚尾性与长记忆性,将广义已实现测度引入偏t分布假设下的Realized GARCH模型与拓展的Realized HAR GARCH模型中,并通过样本内拟合与样本外滚动预测,结合似然函数、VaR后验测试与损失函数MCS检验法综合比较了采用不同已实现测度的Realized GARCH以及Realized HAR GARCH模型在沪铜期货收益波动率估计和VaR预测上的效果。实证结果显示:对于沪铜期货市场而言,无论是波动率估计还是风险预测,广义已实现测度的引入显著地提升了Realized GARCH与Realized HAR GARCH模型的拟合效果与预测能力,其中基于日内损失RMAD与RES测度下的Realized HAR GARCH模型分别拥有最优的估计与预测表现。
基金the project of National Natural Science Foundation of China (Grant No.41004037 and 41202235)
文摘Little attention had been paid to the intracontinental strike-slip faults of the Tibetan Plateau. Since the discovery of the Longriba fault using re-measured GPS data in 2003, an increasing amount of attention has been paid to this neglected fault. The local relief and transverse swath profile show that the Longriba fault is the boundary line that separates the high and flat tomography of the Tibet plateau from the high and precipitous tomography of Orogen. In addition, GPS data shows that the Longriba fault is the boundary line where the migratory direction of the Bayan Har block changed from eastward to southeastward. The GPS data shows that the Longriba fault is the boundary fault of the sub-blocks of the eastern Bayan Har block. We built three-dimensional models containing the Longriba fault and the middle segment of the Longmenshan fault, across the Bayan Har block and the Sichuan Basin. A nonlinear finite element method was used to simulate the fault behavior and the block deformation of the Eastern Tibetan Plateau. The results show that the low resistivity and low velocity layer acts as a detachment layer, which causes the overlying blocks to move southeastward. The detachment layer also controls the vertical and horizontal deformation of the rigid Bayan Har block and leads to accumulation strain on the edge of the layer where the Longmenshan thrust is located. After a sufficient amount of strain has been accumulated on the Longmenshan fault, a large earthquake occurs, such as the 2008 Wenchuan earthquake. The strike slip activity of the Longriba fault, which is above the low resistivity and low velocity layer, partitions the lateral displacements of the Bayan Har block and adjusts the direction of motion of the Bayan Har block, from the eastward moving Ahba sub-block in the west to southeastward moving Longmenshan sub-block in the east. Four models with different depths to the Longriba fault were constructed： （1） a shallow fault with a depth of only 4 km, （2） a deeper fault that is half as deep
基金supported by the National Natural Science Foundation of China(Grant No.40172013)
文摘Three regions can easily be identified in the study area according to the Middle Permian palaeobiogeographic distribution of biota, they are the southern slope of East Kunlun, A’nyêmaqên and Bayan Har. Biotic constitution and ecology in the southern slope of East Kunlun and Bayan Har are very similar. Both the diversity and abundance of organisms in these two areas are very high and reefs are widely developed. However, biotic diversity and abundance in A’nyêmaqên which is between the above two areas are obviously low. Differentiation of palaeo- biogeographic distribution in these areas should be due to the baring of A’nyêmaqên ocean in the time of Middle Permian. Middle Permian radiolarian chert and thick abyssal red ooze are widely spread in A’nyêmaqên, implying that the A’nyêmaqên ocean had a great scale in size. Vast scale of deep ocean basin became an impassable gulf for some of the benthos, and as a result, only part of the organisms could have the chance to get to the isolated islands situated in ocean basin. Small living space and hard conditions in the islands further limited the abundance and diversity of biota. Tectonic background reflected by the geochemical study of basalt in the three areas is coupling well enough with the palaeobiogeographic division.
文摘基于高频数据视角,文章提出时变参数(TV)Realized HAR GARCH混合预测模型,同时考虑资产波动率的聚集性、长记忆以及由测量误差引起的参数衰减偏差效应.进一步,为充分利用价格信息并提升估计效率,本文基于日内“OHLC”数据构建赋权修正已实现信息波动率(WRIV),并将其用于驱动条件方差的动态变化.在偏t分布假设下,以沪深300指数为样本探究中国股票市场的波动性规律,并在实证中评估所提模型在收益率拟合、波动率预测以及风险度量上的能力.结果显示:中国股票市场的收益波动存在明显的异质性与长记忆特征,TV-Realized HAR GARCH能够充分捕捉指数波动率的动态变化,在样本内拟合效果和样本外波动率与风险预测准确性上均能显现出优势,且WRIV测度的引入能显著提升模型的预测精度,凸显出日内高频数据信息的充分利用对于波动率刻画与风险测度的重要性,综合而言,TV-Realized HAR GARCH(WRIV)模型具有最优的整体实证表现.
