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Title:: Fine Geomorphic Interpretation and Quantitative-parameter Extraction of the Active Structure of Mengjiawan of the Tianjingshan Fault Based on UAV Photogrammetric Technique

Author(s):: LIU Chao; DU Peng; LEI Qiyun; WU Zhiqun; LYU Junqiang; YU Sihan; (Earthquake Agency of Ningxia Hui Autonomous Region,Yinchuan 750001,Ningxia,China)

Keywords:: UAV photoqrammetric technique; the Tianjingshan Fault; tectonic landforms; fine interpretation; quantitative parameters

摘要:: 利用无人机摄影测量技术航测天景山断裂孟家湾的地表地形地貌数据,以获取的数字高程模型为基础,通过构造地貌精细解译进一步提取地震断层的水平位移量及垂直位错量,计算断层的平均水平滑动速率,并分析判识了古地震事件。结果表明:①研究区发育3期河流阶地T₃、T₂、T₁,且均被断错,最新的冲沟T₀未见错动; ②在T₁阶地面上提取水平位移量为(7.77±0.98)m,计算得到全新世中期以来的平均水平滑动速率为0.86～0.91 mm/a; ③在T₁阶地面上跨陡坎提取垂直位错量为(0.61±0.11)m,其坡度存在2个明显拐点,代表2次地表破裂型地震事件,推测在12 000 a前,即晚更新世末期或全新世初期以来至少发生过2次地表破裂型地震。

Abstract:: The Unmanned Aerial Vehicle(UAV)photogrammetric technique was used to collect the topographic and geomorphic data of Mengjiawan observatory site in the Tianjingshan Fault in order to get the digital elevation model.Then,through fine interpretation of tectonic geomorphology,the horizontal displacement and vertical dislocation of seismic faults were extracted.The average horizontal slip rate of the fault was calculated,and the paleoseismic events were analyzed and identified.The results show that:①Three stages of river terraces T₃,T₂ and T₁ developed in the study area,and all of them were interrupted,but the latest gully T₀ was not disturbed.②The average,horizontal,slip-rate since the middle of Holocene was 0.86-0.91 mm/a,which was calculated on the basis of the horizontal displacement of(7.77±0.98)m on the T₁ terrace.③The vertical dislocation across the steep ridge on terrace T₁ was(0.61±0.11)m,and the terrace's slope had two obvious inflection points,which represented two seismic events in the form of surface rupture.It was presumed that there had been at least two seismic events in the form of surface rupture since the end of the Late Pleistocene or the beginning of the Holocene,namely 12 000 years ago.