基于密集台阵的海原——六盘山断裂带微震检测与速度结构成像  

Microseismic detection and velocity structure tomography in Haiyuan-Liupanshan fault zone based on a dense array

作　　者：侯郁 汪龙潭 周仕勇[1] HOU Yu;WANG LongTan;ZHOU ShiYong(School of Earth and Space Sciences,Peking University,Beijing 100871,China)

机构地区：[1]北京大学地球与空间科学学院,北京100871

出　　处：《地球物理学报》2025年第3期912-924,共13页Chinese Journal of Geophysics

基　　金：国家重点研发计划(2023YFC3012002);国家自然科学基金(U2039204)资助。

摘　　要：本研究基于布设在青藏高原东北缘海原—六盘山断裂带区域的密集台阵数据记录,应用背景噪声层析成像方法反演得到了2~25 km深度范围内的三维S波速度结构模型.反演结果给出了6个不同深度的水平向速度剖面图和4条横跨断层的垂直向速度剖面图,显示在海原地震震源附近、宁夏固原以北和六盘山断裂带北段分别存在明显低速区.另一方面,利用PALM微震检测程序获得了研究区域自2018年10月至2020年10月的小震目录,在断裂带低速区内部检测到大量小震事件.结合小震震源机制解反演结果,推测在海原断裂带主断层附近存在一系列与主断层正交的小尺度断层结构,小震事件还揭示了断层活动从海原断裂带至六盘山断裂带的空间变化特征,南部区域小震活动空间分布集中,震源深度较浅,北部区域小震活动性更强,震源深度较深.In this study,based on the data recorded by a dense array in the Haiyuan-Liupanshan fault zone on the northeastern margin of the Tibetan Plateau,a three-dimensional S-wave velocity structure model for the depth range of 2~25 km was directly inverted.The inversion results reveal six horizontal velocity profiles at different depths and four vertical velocity profiles across the faults.These profiles highlight the presence of prominent low-velocity zones near the epicenter of the Haiyuan earthquake,to the north of Guyuan,Ningxia,and along the northern segment of the Liupanshan fault zone.Additionally,using the PALM microseismic detection algorithm,a catalog for the study area spanning October 2018 to October 2020 was obtained,identifying numerous microseismic events within the low-velocity zones of the fault system.Combined with the focal mechanism inversion results,it is suggested that a series of small-scale fault structures,orthogonal to the main faults,exist near the Haiyuan fault zone.The microseismic events further reveal the spatial variations in fault activity between the Haiyuan fault zone and the Liupanshan fault zone.In the southern region,the microseismic events are spatially concentrated with shallower focal depths,whereas the northern region exhibits higher seismicity with deeper focal depths.

关 键 词：海原—六盘山断裂带 微震检测 背景噪声成像 密集台阵 

分 类 号：P315[天文地球—地震学]