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中国大陆西部GNSS变形特征及其与M≥7.0强震孕育的关系
武艳强1, 江在森2, 朱爽1, 赵静旸1
1.中国地震局第一监测中心, 天津 300180;2.中国地震局地震预测研究所, 北京 100036
摘要:
基于中国大陆地壳运动观测网络GNSS速度场结果,通过最小二乘配置建模、速度残差检验、应变率场分析等,研究了西部地区地壳变形特征及其与M≥7.0强震孕育的关系。主要认识包括:①GNSS应变率场结果显示青藏高原西部地区(92.5°E以西)呈现明显的EW向拉张变形特征,青藏高原东部(92.5°E~100°E)则表现为显著的EW向挤压应变积累。②GNSS旋转率场显示中国大陆西部呈现由南向北逐渐衰减的交替旋转变形现象,藏南地区为大范围顺时针旋转变形特征,旋转率极值达4.5×10-8rad/a;柴达木地块表现为逆时针旋转变形特征,极值达-1.0×10-8rad/a;塔里木地块表现为顺时针旋转变形特征,极值达1.0×10-8rad/a。③2001~2018年中国大陆西部的7次M≥7.0强震均发生在与其构造背景一致的应变积累高值区边缘,呈现一定的孕震晚期特征。因此,最大剪应变率高值区边缘和大型走滑断裂交界部位、张应变率高值区边缘与大型正断层的交界部位、压应变率高值区边缘与大型逆断层交界部位是未来强震需要关注的地点。④2001年昆仑山口西地震导致了青藏高原东部地区较大尺度EW向挤压应变增强现象,在一定程度上反映了巴颜喀拉地块东向运动增强引起的变形调整过程,有利于汶川地震、芦山地震的孕育发生。
关键词:  地壳变形  青藏高原  GNSS应变率场  最小二乘配置  强震孕育晚期
DOI:
分类号:P315
基金项目:国家重点研发计划(2018YFC1503606)、国家自然科学基金(41974011)共同资助
GNSS Deformation Characteristics and Its Relationship with M≥7.0 Strong Earthquakes in Western China
Wu Yanqiang1, Jiang Zaisen2, Zhu Shuang1, Zhao Jingyang1
1.The First Monitoring and Application Center, CEA, Tianjin 300180, China;2.Institute of Earthquake Forecasting, CEA, Beijing 100036, China
Abstract:
Based on the velocity fields obtained from the Crust Movement Observation Network of China,we analyzed crustal deformation characteristics and its relationship with the M≥7.0 earthquakes in western China by the least squares colocation modeling,velocity residual analysis and strain rate field calculation. The principal results include that: ①the GNSS strain rate field shows clear EW extension in western region of the Tibetan Plateau(west of 92.5°E)and E-W compression in eastern region(92.5°E~100°E). ②the GNSS rotation rate field shows gradually attenuating rotation deformation from the south to the north in western China. Specifically,an extensive clockwise rotation with the maximum value of 4.5×10-8rad/a is dominate in southern Tibet;the Qaidam block is characterized with counterclockwise rotation with the extremum of -1.0×10-8rad/a;the Tarim block is featured with clockwise rotation with the maximum of 1.0×10-8rad/a. ③ all of the seven strong M≥7.0 earthquakes during the period of 2001~2018 in western China occurred at the edge of the high-value zone of strain accumulation consistent with the tectonic background,suggesting the late period characteristics of strong earthquake preparation. Therefore,the junctions of the edge of the high maximum shear strain zone and the large strike slip faulting zone,the edge of the high extension strain zone and the large normal faulting zone,and the edge of the high pressure strain zone and the large reverse faulting zone are the potential places for future strong earthquakes. ④ the 2001 Kunlun earthquake has caused extensive EW compression in the eastern Tibetan Plateau,which reflects a certain extent of the deformation adjustment process caused by the eastward movement of the Bayan Har block,resulting in conducting to the occurrence of Wenchuan and Lushan earthquakes.
Key words:  Crustal deformation  Tibetan Plateau  GNSS strain rate field  Least squares colocation  Late preparation period of strong earthquakes