龙门山中段三维构造建模与恢复及其对隆升机制的浅层响应

The Longmen Shan is a region of steep relief between the eastern Qinghai-Tibet Plateau and the Sichuan basin, which is one of the key areas for the International Continental Dynamics study. After the Wenchuan Ms8.0 earthquake occurred on May 12, 2008, the uplift mechanism and mode of the Longmen Shan inspired a vigorous debate. .The central segment of Longmen Shan is an ideal window to reveal its structure and evolution. In our study, by integrated with the field geological survey, drilling data, the DEM elevation and the seismic data, we will interpret the seismic profiles at the central segment of Longmen Shan and make some quantitative calculation and research for the shallow structures. We use the method of complex structure modeling and balanced section restoration, in order to construct the two-dimensional structural models accurately. .Base on the two-dimensional structural models, many 2D and 3D seismic profiles at the central segment of Longmen Shan will be interpreted. And then the major faults, the folds and the main formations will be constructed as a three-dimensional block model. Based on the Gocad software modeling platform, combined with the rock mechanics parameters and the regional tectonic stress field, we plan to achieve restoration and inspection of the three-dimensional structure model, to make sure the three-dimensional structural model is more reasonable..According to the fault-related fold theory, we will pay more attention to the geometry and kinematics of major faults and focus on the relationship between the co-seismic surface ruptures and the active faults. Reference to the latest deep geophysical research of the Longmen Shan area, our researches intend to analyze the coupling relationship between the deep movement and shallow response, which may provide some important constraints on the dynamical mechanism of uplifting and earthquake in the eastern margin of Qinghai-Tibet Plateau.

龙门山构造带作为青藏高原的东缘，是国际大陆动力学重点研究地区之一。2008年汶川Ms8.0地震发生后，其隆升机制和模式倍受争议和关注。龙门山中段则是揭示龙门山结构和演化比较理想的窗口。本申请将浅表地质、DEM高程、钻井资料结合人工地震数据，对中段地震反射剖面展开精细解释，对浅表构造定量化分析和计算；采用复杂构造建模、平衡剖面等方法，建立适合龙门山中段的二维构造模型。在此基础上，通过大量二维和三维地震解释，建立包括主要断裂、褶皱和岩石地层的三维实体模型。基于Gocad建模平台，综合岩石力学参数、区域构造应力场等，实现龙门山中段的三维构造力学恢复与检验，使三维构造模型更具合理性与科学性。根据断层相关褶皱理论，重点研究主要断裂三维几何学、运动学与同震地表破裂之间的关系；研究龙门山地区深部地球物理探测成果，进一步探讨其深部过程及其浅层响应之间的耦合关系，为研究青藏高原东缘隆升机制提供重要约束。

研究通过区域地质、人工地震反射剖面和钻井资料等，紧紧围绕5.12汶川8级地震发震构造背景为主线，开展地下构造解析，揭示了龙门山中段浅层叠瓦构造变形的特点；分析了龙门山中央断裂带（北川-映秀断裂带）的发震断层及其几何结构；计算了龙门山中段岩层的缩短量约为30% -37%，并解释了彭灌杂岩体（推覆体）下盘构造与地震活动的相关性。在龙门山中段前山带，甄别出彭灌断裂带在汶川地震中的同震破裂断层，建立了较为精细的三维断层模型；运用断层相关褶皱理论，进一步分析了活动断层的几何学、运动学。研究通过龙门山中段前缘单斜带的抬升和变形，揭示基底构造卷入变形；结合深部地球物理资料，分析了深部速度结构与多套滑脱层的控制作用，从深浅耦合的关系提供了龙门山中段隆升的浅层响应以及构造楔入模型。研究分析了龙门山中段新生代的两期构造变形与特征，研究为青藏高原东缘深部动力学和隆升机制提供有力的约束。