摘要
使用布设在龙门山断裂带的宽频台阵记录的P波和S波到时资料和双差走时地震层析成像方法,联合反演龙门山断裂带24 km以上深度的P波和S波三维精细速度结构和地震重新定位。结果显示:(1)龙门山断裂带在北川-映秀断裂和茂县-汶川断裂带之间有一个高速区,0~8 km深度范围内,高速区局限在龙门山断裂带之下;8~20 km深度范围内,高速区与茂县-汶川韧性剪切带高速区相连;20~24 km深度范围内,高速区集中到龙门山断裂带中段。安县-灌县断裂东南侧的川西前陆扩展变形带始终速度较低。(2)龙门山断裂带的地震集中在北川-映秀断裂带之下的4~16 km范围内。地震波速高低转换区和波速比高的区域地震比较集中。地震分布和速度异常的倾斜角度在南段、中段、北段不同,在龙门山断裂带北段,高速体和地震在0~15 km深度范围,倾向几乎垂直。(3)层析速度结构与反射剖面破碎特征联合分析,芦山地震发震区域有一“Y”字形隐伏断裂,上覆10~15 km厚的无震盖层。
Seismic arrival time data from broadband arrays deployed along the Longmenshan fault zone were used to invert three-dimensional fine structure models of VP,VS,and VP/VS at depths less than 24km and earthquake relocation in the Longmenshan fault zone using the consistency-constrained double-difference tomography method.The results are as follows:(1)The Longmen Shan fault zone exhibits a high-velocity zone between the Beichuan-Yingxiu fault and the Maoxian-Wenchuan fault zone.Within the depth range of 0-8km,this high-velocity zone is confined beneath the Longmen Shan fault zone.Between depths of 8-20 km,the high-velocity zone merges with the high-velocity zone associated with the Maoxian-Wenchuan ductile shear zone.At depths ranging from 20-24km,the high-velocity zone becomes concentrated in the central segment of the Longmen Shan fault zone.The Western Sichuan foreland extensional deformation belt on the southeastern side of the Anxian-Guanxian fault maintains consistently low velocities.(2)Earth-quakes within the Longmenshan fault zone are predominantly concentrated at depths ranging from 4 to 16km beneath the Beichuan-Yingxiu fault zone.Seismic activity shows a significant correlation with transitional zones,which signifies shifts between high and low seismic wave velocities as well as regions characterized by elevated velocity ratios.The dip angles of the seismic distribution and velocity anomalies vary across the southern,central,and northern segments of the Longmenshan fault zone.In the northern segment of the Longmenshan fault zone,both high-velocity bodies and earthquakes are concentrated within a depth range of 0-15km,with an almost vertical dip orientation.(3)The combined analysis of tomographic velocity structures and fracture characteristics in the reflection profiles reveals a Y-shaped hidden fault within the seismogenic zone of the Lushan earthquake.The seismogenic area of the Lushan earthquake is overlain by an aseismic zone layer measuring 10-15km thick.
作者
瞿辰
于常青
钱辉
曾祥芝
QU Chen;YU ChangQing;QIAN Hui;ZENG XiangZhi(Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China)
出处
《CT理论与应用研究(中英文)》
2025年第5期775-789,共15页
Computerized Tomography Theory and Applications
基金
地球深部探测与矿产资源勘查国家科技重大专项(郯庐断裂带深井多参数观测井群系统工程建设(2024-ZD1000401))
国家自然科学基金(龙门山断裂带深部结构与断裂剪切带变化特征(4217040898))。
关键词
龙门山断裂带
双差地震层析成像
地壳速度结构
Longmenshan fault zone
double-difference seismic tomography
Crustal Velocity Structure
