摘要
地处青藏高原东南缘的红河断裂及其邻区,地震活动频繁,历史上曾发生过多次地震.2021年发生的漾濞M_(S)6.4级地震就位于该区内.利用红河断裂及邻区的252个台站记录的地震数据以及前人研究得到的面波频散资料,采用面波和接收函数联合扫描方法、经典H-k扫描方法、面波扫描方法,得到研究区的地壳厚度和泊松比,重新构建了红河断裂及邻区的地壳精细结构.研究结果表明,研究区的地壳厚度大致为33~60 km,整体呈现出北高南低的分布特征.地壳最厚在滇中块体北部,达到60 km;最薄的景谷地区仅有28 km.红河断裂带两侧的地壳厚度差异显著,推断与复杂的地质构造活动相关.研究区的泊松比在0.22~0.34之间,呈现出块体分布特征.滇东块体的泊松比总体小于0.26,这与该区的长英质组分较一致.滇中块体北部由于峨眉山大火成岩省的地质活动,使得铁镁质和超铁镁质存在于地壳之中,进而呈现出高泊松比.楚雄地区的泊松比为0.29,地壳厚度为38 km,认为较高的泊松比和地壳“隆起”可能与地下存在熔融物质有关.滇西南地区表现出明显的高泊松比,综合该区的低S波速度结构,推断地下的熔融物质造就了较高的泊松比.地壳厚度和泊松比的变化与板块构造活动和地壳变形相关,这些构造变形也影响着地震的活动性.在地形起伏较大、断层众多的地区,面波和接收函数联合扫描方法具有更高的可靠性.
The Honghe Fault and its adjacent areas are located on the southeastern edge of the Qinghai-Ti-bet Plateau,where earthquake activity is frequent and multiple earthquakes have occurred in history,including the M_(S)6.4 earthquake in Yangbi in 2021.This article utilizes seismic data recorded by 252 stations in the Honghe fault and its neighboring areas,as well as surface wave dispersion data obtained from previous studies,to obtain the crustal thickness and Poisson's ratio of the study area.By using a combination of surface wave and receiver function scanning methods,classical H-k scanning methods,and surface wave scanning methods,a refined structure of the crust in the Honghe fault and its neighboring areas has been reconstructed.The results show that the crustal thickness in the study area is generally between 33-60 km,with a distribution pattern of higher thickness in the north and lower thickness in the south.The thickest crust is found in the northern part of the Dianzhong Block,reaching 60 km,while the thinnest crust is only 28 km thick in the Jinggu area.There is a significant difference in crustal thickness on both sides of the Honghe fault,which is inferred to be related to complex geological tectonic activities.The Poisson's ratio in the study area ranges from 0.22 to 0.34,showing a distribution pattern of different blocks.The Poisson's ratio of the Diandong Block is generally less than 0.26,consistent with the characteristics of the Changning-Menglian terrane.The geological activity of the Emeishan large igneous province in the northern part of the Dianzhong Block has resulted in the existence of ferromagnesian and ultraferromagnesian materials in the crust,leading to a high Poisson's ratio.The Poisson's ratio in the Chuxiong area is 0.29,and the crustal thickness is 38 km.The high Poisson's ratio and“uplift”of the crust are thought to be related to the existence of molten materials underground.The southwestern part of Yunnan Province shows a significant high Poisson's ratio,and the low S-wave velocity structure in the area suggests the existence of molten materials underground.The changes in crustal thickness and Poisson's ratio are related to tectonic activity and crustal deformation,which also affect seismic activity.In areas with significant topographic fluctuations and numerous faults,the combination of surface wave and receiver function scanning methods has higher reliability.
作者
谢夏君
杨海燕
彭恒初
XIE Xia-jun;YANG Hai-yan;PENG Heng-chu(Department of Geophysics,School of Earth Sciences,Yunnan University,Kunming 650500,Yunnan,China)
出处
《云南大学学报（自然科学版）》
CAS
CSCD
北大核心
2023年第S01期367-378,共12页
Journal of Yunnan University(Natural Sciences Edition)
基金
国家自然科学基金(41964002)
云南省教育厅科学研究基金(2022Y012).
关键词
接收函数
面波频散
联合扫描
地壳厚度
泊松比
红河断裂
receiver function
surface wave dispersion
joint scanning
crustal thickness
Poisson's ratio
Honghe fault
