冷龙岭断裂带全新世破裂模式、大震复发周期研究及其区域构造含义

Lenglongling fault zone (LLLFZ) which is adjacent to the “Silk Road Economic Belt” of the “Belt and Road” plays an important role in accommodating tectonic deformation of the northeast Tibetan plateau combining with surrounding active faults of the Qilian-Haiyuan tectonic zone. Nevertheless, there is still a controversy about the Holocene slip rate of the LLLFZ and also we know little about fault rupture pattern and seismic recurrence intervals for a lack of investigation compared with the surrounding faults. A series of offset landforms have been identified from high-resolution remote sensing (HRRS) images, as well as in the fields, which indicate that large earthquakes had ever struck the LLLFZ during the Holocene..This proposal focuses on morphotectonic investigation and determination employing the high-precision terrestrial LiDAR and Unmanned Aerial Vehicle (UAV) photogrammetry methods to resolve the above scientific questions. First of all, detailed structures of landforms across the LLLFZ will be measured to construct the 3D models of the offset landforms, and the pre-earthquake morphologic markers will be matched to constrain fault rupture history. Next, single-event slip and multi-event cumulative will be measured and the relationships between which will be analyzed based on the method of cumulative offset probability density (COPD) to determine potential paleoearthquakes and rupture patterns of the different subsections of the LLLFZ. Meanwhile, the average slip rate will be estimated on base of offset geomorphologic markers and dating results of different segmentations. Finally, seismic recurrence intervals of the different fault segments will be estimated according to the single event slip amounts and the average slip rates of the different parts. All above results will shed light on the investigation of behavior pattern of the LLLFZ..On basis of these studies, we will discuss the tectonic regulating mechanism and its regional tectonic implications of the LLLFZ for the northeast Tibetan plateau by comprehensive analysis of geological, geodesic and geophysical data of previous research. The seismic structural model and tectonic dynamics will be discussed as well. This proposal will be significant for earthquake disaster prevention for the “Belt and Road” of China, and it also will be an important supplement for traditional investigation method of the paleoearthquake.

冷龙岭断裂带的构造变形与地震活动反映了祁连-海原构造带对青藏高原东北缘构造变形的调整作用。目前对冷龙岭断裂带全新世滑动速率仍有争议，对其破裂模式及大震复发周期的认识不足。本申请拟联合地基激光雷达与无人机低空遥感技术，发展基于构造地貌高精度测量的活动断层定量研究方法，进而对以上地震地质问题进行研究。具体研究内容包括构建断层错断地貌三维精细模型，匹配震前地貌标志并恢复断层破裂历史过程；估算错断地貌位移，采用累计位移概率密度法研究地震位移分布关系及断层破裂模式；结合地质样品新年代学测试，估算断层不同部位滑动速率；厘定不同分段单次地震事件位移，明确其全新世大震复发特征。最后综合区域地震地质、大地测量及地球物理资料，分析冷龙岭断裂带在青藏高原东北缘构造变形的调节机制及区域构造含义，探讨该区构造动力学特征。相关研究成果可以为该区“一带一路”的震害防御提供重要依据，也是对古地震传统研究方法的有益补充。

本项目利用多源遥感技术，包括高分辨率光学数据、雷达卫星数据、地基LiDAR点云资料等，对冷龙岭断裂带全新世破裂特征以及2016年门源6.4级地震、2022年门源6.9级地震发震构造与地震地表破裂进行了研究，解析了冷龙岭断裂带大震破裂模式及区域构造模型等科学问题。相关研究成果为2022年门源地震应急调查提供了重要应急支撑，同时为该区域地震灾害风险普查提供重要了参考。.基于地基LiDAR与高分辨率遥感影像，以及累计位移概率密度分布函数法，对沿冷龙岭断裂带不同分段的累计位移进行统计分析，识别出断裂带全新世期间发生的数次古地震事件，其东段单次地震位错规模约8m，全新世期间的平均滑动速率达到6.6±0.3 mm/yr，大震复发间隔约1218 ± 132 yr，冷龙岭断裂带上发生的大震震级约M8.0级，破裂模式符合准周期特征模式。利用哨兵雷达数据处理得到了2016年和2022年门源两次级地震同震形变场，并进行了构造解析。研究表明，2016年地震发生在冷龙岭断裂带北侧分支断层上，地震造成分支断层两侧发生背斜式褶曲隆升。基于国产高分数据对2022年门源6.9级地震地表破裂进行了应急调查，通过进一步解析发现，门源6.9级地震在地表形成了南北两条破裂带，北支沿冷龙岭断裂带主断层西段发育，影像可识别长度约19km；南支沿托莱山断裂东段分布，影像可识别长度约2.3km，最大左旋位移约2.2m。同时反演得到门源6.9级地震震源破裂参数。相关应急产品及信息为地震应急响应与现场调查提供了重要参考。.沿冷龙岭断裂带分布的错断地貌以及两次门源地震事件皆反映了冷龙岭断裂带整体表现为左旋走滑运动特征，该构造变形机制也体现了祁连-海原构造带对青藏高原东北缘的构造调节作用，即来自于青藏板块的构造运动在受到北部戈壁-阿拉善块体及东部华北克拉通块体的阻挡后，在青藏高原东北缘通过一系列左旋走滑断裂的调节，构造运动方向逐渐发生顺时针旋转。最后构建了该区域三维地震构造模型。.本项目建立了基于多源遥感技术的活动断层与构造地貌学定量研究方法，发展了综合遥感、重力与航磁多源信息的活动断层探测与地壳结构反演技术方法与思路，逐步构建了综合多源遥感、重力与航磁资料与方法的活动构造地表地形地貌－浅部结构特征－深部地震构造环境三维研究的技术流程，为开展活动构造探测及震害防御工作提供了思路。