2022年青海门源M_(S)6.9地震地表破裂带宽度调查与启示  

Investigation and implication of the surface rupture width of Menyuan M_(S)6.9 Earthquake in Qinghai Province,2022

作　　者：牛鹏飞 韩竹军[1] 郭鹏[1] 李科长 吕丽星 NIU PengFei;HAN ZhuJun;GUO Peng;LI KeChang;LÜLiXing(Institute of Geology,China Earthquake Administration,Beijing 100029,China)

机构地区：[1]中国地震局地质研究所,北京100029

出　　处：《地球物理学报》2024年第2期548-570,共23页Chinese Journal of Geophysics

基　　金：中国地震局地质研究所基本科研业务专项(IGCEA2206);国家自然科学基金(42002231)资助.

摘　　要：地震地表破裂带是地震破裂在地表的直接表现,其宽度是活断层"避让带"和工程抗震设防重要的指示参数.无人机等测量手段的发展为获取地表破裂带的高分辨率影像数据、精细测量破裂带宽度、分析破裂带宽度空间分布特征以及限定合理的活断层"避让带"提供了有利条件.2022年门源M_(S)6.9地震在青藏高原东北缘冷龙岭与托莱山断裂阶区部位产生了显著的左旋走滑型地表破裂带.基于震后获取的高精度无人机正射影像和数字高程模型,文中在门源地震地表破裂带全段精细解译的基础上,沿走向间隔100 m测量了251个宽度数据,R1破裂带最大宽度为209.78±14 m,平均宽度为42 m,R2破裂带最大宽度为115.31±15.72 m,平均宽度为26.14 m.宽度沿走向具有差异性,这主要受控于同震变形强度、破裂带几何结构以及地表第四系松散层发育状况;具体表现为同震位移量大、阶区等复杂几何结构以及穿过第四系松散层区段的破裂带比同震位移量小、平直段以及基岩区段的破裂带要宽.通过对去除离散值后的破裂带宽度数据统计分析,计算出95.4%和68.2%置信区间的有效宽度分别是70或50 m.在工程抗震设防中,若走滑型活断层评估的最大潜在震级与此次门源地震震级相近(~M 7.0),根据建(构)筑物类别,建议确定"避让带"宽度时参考本文获得的破裂带有效宽度(70或50 m).对于单一走滑型错动面发育地段,按建(构)筑物类别向两侧各扩展35或25 m即可;而对于活断层斜列阶区、平行断层围限区、走向弯曲区和双陡倾角错动面发育地段,在这些复杂几何结构分布范围的基础上需要各向两侧扩展35或25 m.本文研究结果可为建(构)筑物选址避让走滑型断层提供参考依据.The surface rupture zone is the direct manifestation of an earthquake on the Earth's surface,and its width is an important parameter for the active fault's"avoidance zone"and seismic engineering design.The development of remote sensing technology such as unmanned aerial vehicle detection has promoted the research of surface rupture zone,including obtaining high-resolution image data,accurately measuring their width,analyzing their spatial distribution,and defining a reasonable"avoidance zone"for the active fault.The 2022 Menyuan M_(S)6.9 earthquake created a significant left-lateral surface rupture zone in the stepover of the Lenglongling and Tuolaishan faults along the northeastern margin of the Tibetan Plateau.In this study,we conducted a detailed interpretation of the earthquake's surface rupture zone based on high-resolution unmanned aerial vehicle orthoimages and digital elevation models obtained after the earthquake.We measured the rupture zone's width every 100 m along the fault strike and got 251 width data points.The maximum and average width of the R1 rupture zone are 209.78±14 m and 42 m respectively and are 115.31±15.72 m and 26.14 m at the R2 rupture zone respectively.According to the spatial distribution of the above data,we believe that the surface rupture zone's width shows significant variations along the fault strike,which is mainly controlled by the distribution of Quaternary loose deposits,the geometric structure of the faults,and their coseismic deformation.Specifically,the surface rupture zone is wider in the areas with Quaternary loose deposits,complex fault structures,and larger coseismic displacement,while it is narrower in the areas with the fault cut through bedrock,relatively straight fault segments,and smaller coseismic displacement.Based on the statistics of the rupture zones'width after removing the data's outliers,we conclude that the effective widths at 95.4%and 68.2%confidence intervals are approximately 70 or 50 m,respectively.For this reason,we suggest that the"avoidance zone

关 键 词：走滑型地震 地震地表破裂带 活断层"避让带"宽度 门源M_(S)6.9地震 工程抗震设防 

分 类 号：P315[天文地球—地震学] P313[天文地球—固体地球物理学]