摘要
本研究利用中国国家地震台网336个固定地震台站记录的远震波形资料,通过P波接收函数H-κ分析估算了中国华南地区的地壳厚度和地壳平均波速比.研究结果显示,地壳厚度约为25~46 km,整体表现西深东浅的变化特点.研究区地壳厚度变化分别与布格重力异常和地形呈现负相关和正相关.扬子块体东部显示较低地壳波速比(<1.7)可能与地表沉积岩的存在相关.四川盆地内部的平均地壳波速比(约1.71~1.8)与全球大陆地盾/克拉通地区相当.但其周围地区地壳平均波速比明显增高(1.81~1.95),推测可能是克拉通形成过程中岩浆的底侵引起下地壳组分以铁镁质麻粒岩为主.华夏块体西部表现为薄的地壳厚度和低的地壳平均波速比(1.65~1.75),暗示该区基性下地壳物质的缺失可能与增厚的地壳发生拆沉有关.华夏块体东南段呈现出较高的地壳平均波速比(约1.77~1.86),地壳组成以中基性铁镁质为主,推断可能与晚中生代铁镁质岩浆底侵作用密切相关.
Crustal thicknesses and averaged VP/VS ratios in South China were estimated using the receiver function H-κstacking method.In this process,high-quality telesiesmic P-wave receiver functions were calculated from data recorded at 336 permanent stations.Results show that the crustal thicknesses,ranging from about 25 to about 46 km,are deeper in the west and shallower in the east of the study region.They have negative and positive correlations with Bouguer gravity anomalies and elevations,respectively.Low average crustal VP/VS ratios(<1.7)beneath the eastern Yangtze block could be related with the presence of surface sedimentary rocks.In the Sichuan basin,the mean crustal VP/VS ratios(about 1.71~1.8)are generally consistent with those in global shields/cratons.The distinct increasing of V P/V S ratios(1.81~1.95)near the Sichuan basin and surrounding areas,however,is consistent with geological observation of mafic granulite in the lower crust,which is associated with magmatic underplating during the formation of craton.The western Cathaysia block is characterized with thinner crustal thicknesses and lower average VP/VS ratios(1.65~1.75),implying that the absence of the mafic lower crust may be associated with delamination of the lower crust.The higher values of VP/VS ratios(about 1.77~1.86)beneath the southeastern Cathaysia block is indicative of the predominantly intermediate-to-mafic crust,which may be related to mafic magmatic underplating during the Late Mesozoic.
作者
杨晓瑜
李永华
YANG XiaoYu;LI YongHua(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Key Laboratory of Earthquake Source Physics,China Earthquake Administration,Beijing 100081,China)
出处
《地球物理学报》
SCIE
EI
CAS
CSCD
北大核心
2021年第1期146-156,共11页
Chinese Journal of Geophysics
基金
国家自然科学基金地震科学联合基金(U1839210)资助.
关键词
接收函数
H-κ叠加
地壳厚度
波速比
华南地区
Receiver functions
H-κstacking
Crustal thicknesses
VP/VS ratios
South China
