The Earth’s surface kinematics and deformation are fundamental to understanding crustal evolution.An effective research approach is to estimate regional motion field and deformation fields based on modern geodetic ne...The Earth’s surface kinematics and deformation are fundamental to understanding crustal evolution.An effective research approach is to estimate regional motion field and deformation fields based on modern geodetic networks.If the discrete observed velocity field is obtained,the velocity related fields,such as dilatation rate and maximum shear strain rate,can be estimated by applying varied mathematical approaches.This study applied Akaike's Bayesian Information Criterion(ABIC)method to calculate strain rate fields constrained by GPS observations in the southeast Tibetan Plateau.Comparison with results derived from other three methods revealed that our ABIC-derived strain rate fields were more precise.The maximum shear strain rate highlighted the Xianshuihe–Xiaojiang fault system as the main boundary for the outward migration of material in southeastern Tibet,indicating rotation of eastern Tibet material around the eastern Himalaya rather than whole extrusion along a fixed channel.Additionally,distinct dilatation rate patterns in the northeast and southwest regions of the fault system were observed.The northeast region,represented by the Longmenshan area,exhibited negative dilatational anomalies;while the southwest region,represented by the Jinsha River area north of 29°N,displayed positive dilatational anomalies.This indicates compression in the former and extension in the latter.Combined with deep geophysical observations,we believe that the upper and lower crusts of the Jinsha River area north of 29°N are in an entire expanding state,probably caused by the escape-drag effect of material.The presence of a large,low-viscosity region south of 29°N may not enable the entire escape of the crust,but instead result in a differential escape of the lower crust faster than the upper crust.展开更多
太阳黑子变化是太阳强磁扰动的表征。结合长短期记忆单元神经网络和一维卷积神经网络预测太阳黑子变化,使用3种不同的数据集,分别为1700—2020年年均太阳黑子数(yearly mean sunspot number,YSSN)、1749—2021年月均太阳黑子数(monthly ...太阳黑子变化是太阳强磁扰动的表征。结合长短期记忆单元神经网络和一维卷积神经网络预测太阳黑子变化,使用3种不同的数据集,分别为1700—2020年年均太阳黑子数(yearly mean sunspot number,YSSN)、1749—2021年月均太阳黑子数(monthly mean sunspot number,MSSN)和1874—2021年月均太阳黑子面积(monthly mean sunspot area,MSSA)。首先,基于YSSN数据集,预测得到2021年YSSN以及第25太阳周YSSN,2025年预测值达到最大,其值为163.4;其次,基于MSSN数据集,预测得到2021年6月MSSN以及第25太阳周MSSN,2024年10月预测值达到最大,其值为245.9;接着,基于MSSA数据集,预测得到2021年6月MSSA,其值为73.1;最后,基于MSSA数据集,将纬度划分为13个分区,发现可以重建太阳黑子蝴蝶图。以上均表明神经网络方法为探测太阳黑子变化提供了新的解决思路。展开更多
The relationship between the strain rate field observed by GPS and global distribution of strong earthquakes is analyzed in this work. How do we recognize the characteristics of global seismic activities with space ob...The relationship between the strain rate field observed by GPS and global distribution of strong earthquakes is analyzed in this work. How do we recognize the characteristics of global seismic activities with space observation technology? A preliminary model of Cellular Automata that could simulate the global seismic activities both in time and space has been established based on the results of global strain rate field provided by the GSRM Program. The grid of the model is evenly divided,which is consistent with that of GSRM.The status of each cell is its strain state,and is adjusted according to the evolution rules.Maximum shear strain criterion is adopted in the evolution of the Cellular Automata. The threshold for cells in surface expansion is 80% of that for those in compression. The preliminary model could in general simulate the main characteristics of the distribution of the global seismic activities. It could exhibit in general the global distribution of weak and active tectonic activities. Although the preliminary Cellular Automata model needs to be improved in many aspects,the result suggests the possibility of modeling the general features of rather complicated global seismic activities based on the strain rates obtained by GPS and other observations.展开更多
In order to explore the abnormal variations before and after the Wen'an M5. 1 earthquake on July 4,2006,the gravity data observed by the Wenba Gravity Observation Network before and after the earthquake was analyz...In order to explore the abnormal variations before and after the Wen'an M5. 1 earthquake on July 4,2006,the gravity data observed by the Wenba Gravity Observation Network before and after the earthquake was analyzed. The relationships between gravity change and vertical displacement and shallow groundwater level were discussed,and elevation correction of the gravity was preliminarily performed. The results show that there were abnormal gravity changes before the M5. 1 earthquake,which appeared as gravity rising in the whole observation network,especially in the south part. A high gradient of gravity variation appeared around the epicenter before the M5. 1 earthquake,especially during the short period between October 2005 to April 2006. The boundary of the positive and negative gravity variations gradually deflected and began to recover from October 2007.展开更多
The November 14,2001 M_S8.1 Kunlun Mountains earthquake in northern Tibet is the largest earthquake occurring on the Chinese mainland since 1950.We apply a three-dimensional(3-D)finite element numerical procedure to m...The November 14,2001 M_S8.1 Kunlun Mountains earthquake in northern Tibet is the largest earthquake occurring on the Chinese mainland since 1950.We apply a three-dimensional(3-D)finite element numerical procedure to model the coseismic displacement and stress fields of the earthquake based on field investigations.We then further investigate the stress interaction between the M_S8.1 earthquake and the intensive aftershocks.Our primary calculation shows that the coseismic displacement field is centralized around the east Kunlun fault zone.And the attenuation of coseismic displacements on the south side of Kunlun fault zone is larger than that on the north side.The calculated coseismic stress field also indicates that the calculated maximal shear stress field is centralized around the east Kunlun fault zone;the directions of the coseismic major principal stress are opposite to that of the background crustal stress field of the Qinghai-Xizang(Tibet)Plateau.It indicates that the earthquake relaxes the crustal stress state in the Qinghai-Xizang(Tibet)Plateau.Finally,we study the stress interaction between M_S8.1 earthquake and its intensive aftershocks.The calculated Coulomb stress changes of the M_S8.1 great earthquake are in favor of triggering 4 aftershocks.展开更多
From Global Position System(GPS) measurements,there is a clockwise rotation around the eastern Himalayan syntax in the Tibetan Plateau.This phenomenon is difficult to be interpreted by simple two-dimensional modeling ...From Global Position System(GPS) measurements,there is a clockwise rotation around the eastern Himalayan syntax in the Tibetan Plateau.This phenomenon is difficult to be interpreted by simple two-dimensional modeling from a geodynamic point of view.Because of the extremely thick crust and the lower crust with relatively high temperature in the Tibetan Plateau,the lithospheric rheology in Tibet and surrounding areas present a complex structure.In general,the tectonic structure of the Tibetan Plateau consists of brittle upper crust,ductile lower crust,high viscosity lithospheric upper mantle,and low viscosity asthenosphere,the same as the case in many other continental regions.However,the lower crust in the Tibetan Plateau is much more ductile with a lower viscosity than those of its sur-roundings at the same depth,and the effective viscosity is low along the collision fault zone.In this study,we construct a three-dimensional Maxwell visco-elastic model in spherical coordinate system,and simulate the deformation process of the Tibetan Plateau driven by a continuous push from the Indian plate.The results show that the existence of the soft lower crust under the plateau makes the entire plateau uplift as a whole,and the Himalayas and the eastern Himalayan syntax uplift faster.Since the lower crust of surrounding blocks is harder except in the southeastern corner where the high-temperature material is much softer and forms an exit channel for material transfer,after the whole plateau reaches a certain height,the lower crustal and upper mantle material begins to move eastward or southeastward and drag the upper crust to behave same way.Thus,from the macroscopic point of view,a relative rigid motion of the plateau with a clockwise rotation around the eastern Himalayan syntax is developed.展开更多
基金supported by grants from the Ministry of Science and Technology(Grant Nos.2021FY100101,2019QZKK0901)the National Natural Science Foundation of China(Grant Nos.41941016,42230312,42020104007)China Geological Survey(Grant No.DD20221630).
文摘The Earth’s surface kinematics and deformation are fundamental to understanding crustal evolution.An effective research approach is to estimate regional motion field and deformation fields based on modern geodetic networks.If the discrete observed velocity field is obtained,the velocity related fields,such as dilatation rate and maximum shear strain rate,can be estimated by applying varied mathematical approaches.This study applied Akaike's Bayesian Information Criterion(ABIC)method to calculate strain rate fields constrained by GPS observations in the southeast Tibetan Plateau.Comparison with results derived from other three methods revealed that our ABIC-derived strain rate fields were more precise.The maximum shear strain rate highlighted the Xianshuihe–Xiaojiang fault system as the main boundary for the outward migration of material in southeastern Tibet,indicating rotation of eastern Tibet material around the eastern Himalaya rather than whole extrusion along a fixed channel.Additionally,distinct dilatation rate patterns in the northeast and southwest regions of the fault system were observed.The northeast region,represented by the Longmenshan area,exhibited negative dilatational anomalies;while the southwest region,represented by the Jinsha River area north of 29°N,displayed positive dilatational anomalies.This indicates compression in the former and extension in the latter.Combined with deep geophysical observations,we believe that the upper and lower crusts of the Jinsha River area north of 29°N are in an entire expanding state,probably caused by the escape-drag effect of material.The presence of a large,low-viscosity region south of 29°N may not enable the entire escape of the crust,but instead result in a differential escape of the lower crust faster than the upper crust.
基金supported by National Basic Research Program of China(2008cb425701)National Science Foundation of China under grants number(40774049)Knowledge Innovation Project of Chinese Academyof Sciences(kzcx2-yw-123)
文摘太阳黑子变化是太阳强磁扰动的表征。结合长短期记忆单元神经网络和一维卷积神经网络预测太阳黑子变化,使用3种不同的数据集,分别为1700—2020年年均太阳黑子数(yearly mean sunspot number,YSSN)、1749—2021年月均太阳黑子数(monthly mean sunspot number,MSSN)和1874—2021年月均太阳黑子面积(monthly mean sunspot area,MSSA)。首先,基于YSSN数据集,预测得到2021年YSSN以及第25太阳周YSSN,2025年预测值达到最大,其值为163.4;其次,基于MSSN数据集,预测得到2021年6月MSSN以及第25太阳周MSSN,2024年10月预测值达到最大,其值为245.9;接着,基于MSSA数据集,预测得到2021年6月MSSA,其值为73.1;最后,基于MSSA数据集,将纬度划分为13个分区,发现可以重建太阳黑子蝴蝶图。以上均表明神经网络方法为探测太阳黑子变化提供了新的解决思路。
基金sponsored by the National Key Techonology R&D Program(2012BAK19B01)the National Natural Foundation of China(41274098)
文摘The relationship between the strain rate field observed by GPS and global distribution of strong earthquakes is analyzed in this work. How do we recognize the characteristics of global seismic activities with space observation technology? A preliminary model of Cellular Automata that could simulate the global seismic activities both in time and space has been established based on the results of global strain rate field provided by the GSRM Program. The grid of the model is evenly divided,which is consistent with that of GSRM.The status of each cell is its strain state,and is adjusted according to the evolution rules.Maximum shear strain criterion is adopted in the evolution of the Cellular Automata. The threshold for cells in surface expansion is 80% of that for those in compression. The preliminary model could in general simulate the main characteristics of the distribution of the global seismic activities. It could exhibit in general the global distribution of weak and active tectonic activities. Although the preliminary Cellular Automata model needs to be improved in many aspects,the result suggests the possibility of modeling the general features of rather complicated global seismic activities based on the strain rates obtained by GPS and other observations.
基金Supported by the Technology Research and Development Program of Institute of Earthquake Science, CEAthe National Key Technology R&D Program(2006BAC01B02-02),China
文摘In order to explore the abnormal variations before and after the Wen'an M5. 1 earthquake on July 4,2006,the gravity data observed by the Wenba Gravity Observation Network before and after the earthquake was analyzed. The relationships between gravity change and vertical displacement and shallow groundwater level were discussed,and elevation correction of the gravity was preliminarily performed. The results show that there were abnormal gravity changes before the M5. 1 earthquake,which appeared as gravity rising in the whole observation network,especially in the south part. A high gradient of gravity variation appeared around the epicenter before the M5. 1 earthquake,especially during the short period between October 2005 to April 2006. The boundary of the positive and negative gravity variations gradually deflected and began to recover from October 2007.
基金The research was sponsored by the"Basic Scientific Research Plan"(02076902-03) of Institute of Earthquake Science, China Earthquake Administrationby grants from the Chinese Ministry of Science and Technology (2004CB418406, 2005DKA64000).
文摘The November 14,2001 M_S8.1 Kunlun Mountains earthquake in northern Tibet is the largest earthquake occurring on the Chinese mainland since 1950.We apply a three-dimensional(3-D)finite element numerical procedure to model the coseismic displacement and stress fields of the earthquake based on field investigations.We then further investigate the stress interaction between the M_S8.1 earthquake and the intensive aftershocks.Our primary calculation shows that the coseismic displacement field is centralized around the east Kunlun fault zone.And the attenuation of coseismic displacements on the south side of Kunlun fault zone is larger than that on the north side.The calculated coseismic stress field also indicates that the calculated maximal shear stress field is centralized around the east Kunlun fault zone;the directions of the coseismic major principal stress are opposite to that of the background crustal stress field of the Qinghai-Xizang(Tibet)Plateau.It indicates that the earthquake relaxes the crustal stress state in the Qinghai-Xizang(Tibet)Plateau.Finally,we study the stress interaction between M_S8.1 earthquake and its intensive aftershocks.The calculated Coulomb stress changes of the M_S8.1 great earthquake are in favor of triggering 4 aftershocks.
基金Supported by Knowledge Innovation Project of the Chinese Academy of Sciences (Grant No.KZCX2-YW-123)National Natural Science Foundation of China (Grant Nos.40774048 and 90814014)
文摘From Global Position System(GPS) measurements,there is a clockwise rotation around the eastern Himalayan syntax in the Tibetan Plateau.This phenomenon is difficult to be interpreted by simple two-dimensional modeling from a geodynamic point of view.Because of the extremely thick crust and the lower crust with relatively high temperature in the Tibetan Plateau,the lithospheric rheology in Tibet and surrounding areas present a complex structure.In general,the tectonic structure of the Tibetan Plateau consists of brittle upper crust,ductile lower crust,high viscosity lithospheric upper mantle,and low viscosity asthenosphere,the same as the case in many other continental regions.However,the lower crust in the Tibetan Plateau is much more ductile with a lower viscosity than those of its sur-roundings at the same depth,and the effective viscosity is low along the collision fault zone.In this study,we construct a three-dimensional Maxwell visco-elastic model in spherical coordinate system,and simulate the deformation process of the Tibetan Plateau driven by a continuous push from the Indian plate.The results show that the existence of the soft lower crust under the plateau makes the entire plateau uplift as a whole,and the Himalayas and the eastern Himalayan syntax uplift faster.Since the lower crust of surrounding blocks is harder except in the southeastern corner where the high-temperature material is much softer and forms an exit channel for material transfer,after the whole plateau reaches a certain height,the lower crustal and upper mantle material begins to move eastward or southeastward and drag the upper crust to behave same way.Thus,from the macroscopic point of view,a relative rigid motion of the plateau with a clockwise rotation around the eastern Himalayan syntax is developed.
