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利用强震震源机制解资料反演中国大陆及其邻区的形变场模型
李长军1),任金卫2),周琳1),秦姗兰1),柴旭超1)
1)中国地震局第二监测中心,西安 710054;2)中国地震局地震预测研究所,北京 100036
摘要:
搜集了1900-2013年间发生在中国大陆及其邻区的震源机制解资料,详细整理了其中的70个7级及以上大震的震源参数、地表破裂带和地表位移资料。根据资料的完整程度将地震分成三类:A类存在地表破裂和地表位移观测资料;B类存在地表破裂资料,但缺少地表位移观测数据;C类缺少地表破裂带和地表位移观测资料。对B类和C类缺少地表位移观测数据的地震,利用三角形模型模拟其位移分布。再根据地表位移分布及地震破裂带与本文使用网格模型之间的位置关系将地震分段。最后,利用分段前、后的地震数据和改进的双三次样条方法反演研究区域的形变场模型。结果表明:①大震资料的分段处理改进了地震数据的反演结果,提高了反演模型的合理性和空间一致性;在喜马拉雅断裂带,形变场具有更好的连续性,其变形特征与地质等数据的反演结果基本吻合;塔里木盆地和阿尔金断裂的形变量减小,与该区域较低的地震活动性一致;戈壁—阿尔泰的变形从SE的挤压和NE的拉张调整到NE的挤压和NW的拉张;鄂尔多斯西缘的拉张分量明显减小。②113年的地震资料解释了印度板块向欧亚板块运动总速率的30~50%,存在20mm/a左右的速度亏损,该亏损量可能包括断层蠕动、褶皱等非震形变,未监测到或者缺失的地震,及以弹性应变能形式存在通过潜在地震释放的应变。
关键词:  形变场模型  震源机制解  双三次样条函数  大震分段  应变率场  中国大陆
DOI:
分类号:
基金项目:
Deformation Model Inferred from Focal Mechanisms in the Chinese Mainland and Its Adjacent Areas1
Li Zhangjun1,2),Ren Jinwei2),Zhou Lin1),Qin Shanlan1),and Chai Xuchao1)
1) Second Monitoring and Application Center,CEA,Xian 710054,China;2) Institute of Earthquake Science,CEA,Beijing 100036,China
Abstract:
We collect seismic moment tensors of the earthquakes occurring from 1900 to 2013 in and around the Chinese mainland and summarize the surface ruptures and displacements of 70 earthquakes with MS≥7. 0. We divide these large earthquakes into three types. Type A contains earthquakes with surface ruptures and displacements. Type B is earthquakes without displacements and Type C is those without any of this data. We simulate a triangular distribution of displacements for Type B and C. Then,we segment these large earthquakes by using their displacements and surface ruptures. Finally,kinematic models are determined from earthquake data and Bicubic Bessel spline functions. The results show that,first of all,the reasonability and spatial consistency of defined models are advanced. Strain rates have better continuity and are comparable with geologic and geodetic results in Himalaya thrust fault zones. The strain rates decrease in the Tarim basin and the Altun Tagh fault zones because of their low seismicity. The direction of compressional deformation in Gobi-Altay is changed from SE to NE and its extensional direction is changed from NE to NW. The extensional deformation in the Ordos block is diminished obviously. Secondly,earthquakes account for 30-50% of expected motion of India relative to Eurasia determined from the NUVEL-1A model,with a missing component of 20mm/a which may contain aseismic deformation such as fault creep and folds,the missing parts of earthquake data and elastic strain energy released by potential earthquakes.
Key words:  Bicubic  Bessel spline function  Earthquake segmentation  Kinematic model  Surface rupture