巽他大陆及其邻区的地壳结构及其构造意义:来自远震接收函数的约束  

Crustal structure and its tectonic implications in Sundaland and adjacent areas:Constraints from tele-seismic receiver functions

作　　者：冯铭业 陈凌[1,2] 王旭 韦生吉[3] 王新 FENG MingYe;CHEN Ling;WANG Xu;WEI ShengJi;WANG Xin(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049,China;Earth Observatory of Singapore,Nanyang Technological University,Singapore 639798,Singapore;Key Laboratory of Earth and Planetary Physics,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China)

机构地区：[1]岩石圈演化国家重点实验室,中国科学院地质与地球物理研究所,北京100029 [2]中国科学院大学地球与行星科学学院,北京100049 [3]Earth Observatory of Singapore,Nanyang Technological University,Singapore 639798,Singapore [4]中国科学院地球与行星物理重点实验室,中国科学院地质与地球物理研究所,北京100029

出　　处：《地球物理学报》2021年第12期4364-4377,共14页Chinese Journal of Geophysics

基　　金：国家自然科学基金基础科学中心项目(41688103);中国科学院战略性先导科技专项(A类)项目子课题(XDA20070302)资助.

摘　　要：巽他大陆位于欧亚板块、印度—澳大利亚板块和太平洋板块俯冲汇聚区域,其地壳结构特征是揭示洋陆过渡带演化及物质能量交换机制的重要依据.本文对巽他大陆及其周缘19个宽频带地震台站记录的远震波形进行P波接收函数分析和H-κ叠加处理,获取了每个台站下方的地壳厚度和平均地壳波速比信息.为了减少参数的主观选择对结果带来的不确定性,研究采用了多种参数组合、综合约束策略.将本文结果与前人146个宽频带台站接收函数的研究结果进行整合,我们获得了巽他大陆地区地壳厚度和平均地壳波速比分布,并统计分析了两者的相关性.结果显示:巽他大陆地壳总体较薄,平均地壳厚度约为32 km,远低于全球造山带平均值,而与全球拉张型地壳平均厚度较为接近,可能反映研究区地壳整体处于拉张应力状态;而呵叻高原盆地地区地壳相对较厚,平均约38 km,与周缘地区明显不同.火山弧地区平均地壳波速比普遍大于1.81,甚至达1.87以上,并且壳内广泛分布低速层,可能受到了火山弧地区熔融物质的影响;非火山弧地区平均地壳波速比则普遍小于1.76,反映地壳组分以长英质成分为主;局部地区高于1.81,甚至高达1.99,表明地壳以铁镁质成分为主或存在部分熔融,可能与铁镁质岩浆底侵作用或地幔热物质上涌有关.中南半岛中西部、婆罗洲西北部和马来半岛中部莫霍面Ps转换波和多次波不明显而且具有多峰特征,可能表明该区域经历了复杂的壳幔相互作用.巽他大陆地区地壳厚度和平均地壳波速比总体无明显相关性,说明上地壳和下地壳结构和成分横向变化复杂;但中南半岛内部呵叻高原附近和东南部火山区两者均呈负相关性,与周围地区明显不同.综合区域构造背景和其他多种地球物理观测,推测稳定的呵叻高原盆地阻挡了印支地块的侧向挤出,处于挤压应力环境并发生上�The crustal structure in Sundaland,where the Eurasian,Indo-Australian and Pacific plates are converged,is of great importance to understanding the tectonic evolution of continent-ocean transitions and associated material recycling and energy exchange.In this study,we analyze the P-wave receiver function waveforms of 19 broadband seismic stations in Sundaland and apply the H-κstacking technique to estimate both crustal thickness and average V P/V S ratio.Different processing parameters are jointly employed to reduce the uncertainty of H-κestimation.We then combine previous results from 146 broadband stations to obtain the spatial variation of crustal thickness and V P/V S ratio,as well as their correlations.The results show that the average crustal thickness is about 32 km in Sundaland,obviously less than the global average beneath orogenic belts but close to that beneath extensional areas,suggesting that the crust in the region has been extended and thinned.A thicker crust with an average of 38 km,however,can be found beneath the Khorat plateau basin.In the volcanic arcs,the V P/V S ratio is significantly high(>1.81 and even>1.87),spatially corresponding to the regions where low velocity layers appear within the crust,probably indicating the existence of partially molten materials.In non-volcanic areas,the crustal V P/V S ratios are generally less than 1.76,although relatively high V P/V S ratios(>1.81 and even reach up to 1.99)appear in some local areas.Therefore,we infer that the crust is dominantly felsic in composition in Sundaland,but in some local areas,the crust is dominated by mafic composition or partial melting due to the underplating and upwelling of basaltic magma.P-wave receiver function waveforms present double or multiple peaks at the arrivals around the Ps and PpPs phases in midwestern Indochina,northwestern Borneo and middle Malay peninsula,where we speculate that the crust and mantle have interacted strongly with each other.We do not observe a clear correlation between the crustal thickness an

关 键 词：巽他大陆 接收函数 地壳厚度 地壳波速比 洋陆过渡带 

分 类 号：P541[天文地球—构造地质学] P315[天文地球—地质学]