摘要
北京时间2021年5月22日02时04分,在青海省果洛藏族自治州玛多县发生M_(W)7.3地震.本文利用震中及邻区2009—2021年GNSS观测资料,研究了此次地震的区域孕震环境、同震和震后初期的变形特征.首先,给出了较高空间分辨率的GNSS速度场,表明震中及其邻区的构造活动以左旋剪切为主,巴颜喀拉块体南北两侧的相对运动是块体边界断裂和块体内部级次断层的综合响应,其中边界断裂的相对运动占到了整个块体相对运动的57%,块体内部相对运动占到43%.其次,利用顾及抗差性的多尺度球面小波方法解算了GNSS应变率场,结果表明主要的应变积累区域沿着巴颜喀拉块体的主边界断裂分布,震中位于应变高值区向低值区的过渡带.最后,利用GNSS连续观测站资料给出了此次地震的同震和QHMD连续观测站的震后初期位移,采用两种策略解算了同震位移,对比研究表明,利用震后4 h时长数据的策略获得了更为准确的同震位移,而单日解的结果中更多地包含了快速变化的震后变形.青海玛多(QHMD)测站观测到了25 cm的同震位移和明显的震后位移,利用表征震后余滑的对数衰减模型能够准确拟合震后变形观测值,发现震后初期5天内的变形量占到了初期20天内的72%.
The Madoi M_(W)7.3 earthquake occurred at 02∶04 local standard time on May 22,2021,in Madoi County,Tibetan Autonomous Prefecture of Golog,Qinghai Province.In this paper,the regional seismogenic environment,coseismic displacements,and early postseismic deformation evolution are studied by using the long term accumulated GNSS observations of the epicenter and its surrounding areas.Firstly,we obtained the horizontal GNSS velocity field,which indicated the seismogenic environment of the epicenter and its surrounding areas is mainly sinistral shear.The relative crustal deformation of the main boundary fault accounts for 57%of the relative movement of the whole Bayan Har block,while the internal one accounts for 43%.Secondly,we calculated the GNSS strain rate field by using multi-scale spherical wavelet method considering robustness.The result shows that the significant strain accumulation areas are distributed along the main boundary fault of the block,and the epicenter is located on the transition zone from the great strain rate values to the low one.Finally,the coseismic and early postseismic deformation was calculated by continuous GNSS observations.Two strategies were adopted to calculate the coseismic displacements,the difference between them indicated the coseismic displacements can be obtained more accurately by using the strategy of 4 hours observations after the mainshock,and the results of single day strategy have included the early postseismic deformation.The significant postseismic deformation was obtained at station QHMD,and its direction is consistent with the coseismic one.The logarithmic attenuation model which characterizes mainly after-slip deformation can accurately model the observed values.The postseismic deformation in the first 5 days accounts for 72%of the first 20 days.
作者
苏小宁
熊仁伟
孟国杰
郭楠
杨维芳
李毓照
吴伟伟
赵国强
SU XiaoNing;XIONG RenWei;MENG GuoJie;GUO Nan;YANG WeiFang;LI YuZhao;WU WeiWei;ZHAO GuoQiang(Faculty of Geomatics,Lanzhou Jiaotong University,Lanzhou 730070,China;Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100036,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2022年第3期1032-1043,共12页
Chinese Journal of Geophysics
基金
国家自然科学基金(42174003、41874024)
甘肃省青年人才托举工程(GXH20210611-06)
兰州交通大学青年科学基金(2021003)联合资助。
