四川盆地及邻区地壳分层结构研究——基于接收函数改进的序贯H-κ叠加方法的约束  

Crustal layering in Sichuan basin and surrounding regions:Constraint from improved sequential H-κstacking of receiver functions

作　　者：张笑晗 张瑞青[1] 朱敏 ZHANG XiaoHan;ZHANG RuiQing;ZHU Min(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China)

机构地区：[1]中国地震局地球物理研究所,北京100081

出　　处：《地球物理学报》2024年第8期2946-2962,共17页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41874073);中国地震局地球物理研究所基本科研业务专项(DQJB20R35)共同资助。

摘　　要：接收函数H-κ叠加方法已被广泛应用于单个台站下方地壳结构的研究中.为探测盆地的沉积层和结晶地壳结构,一些研究提出了序贯H-κ叠加方法.但在实际应用中,往往需要人工区分存在沉积层的台站和基岩台站,分别应用序贯H-κ叠加和常规H-κ叠加方法.这种处理方式效率相对要低.为了克服这一局限性,本文对序贯H-κ叠加方法进行了一些改进,理论测试分析表明,该方法能够同时适用于单层和双层地壳模型,易于对大批量数据进行快速分析.其次,本文利用四川盆地及邻区近7年来的区域固定台站资料,以及威远地区布设的流动台网数据,基于改进的序贯H-κ叠加方法,对研究区地壳内部分层结构进行了研究.结果显示,盆地中北部地区沉积层厚度为4.6~6.7 km,平均V_(P)/V_(S)值约1.9~2.9.盆地南部一些台站下方观测到了康拉德界面,埋深约21~25 km,进而估算上地壳占整个地壳厚度的比例约56%.研究还发现,龙门山断裂带两侧地壳厚度变化明显,且断裂带南段地壳平均V_(P)/V_(S)值略高.此外,华蓥山断裂带局部地区下方呈现双Moho结构.H-κ stacking with receiver functions has been widely adopted in extracting crustal structure beneath a single station.To constrain sediment and basement crustal structure beneath basins,a sequential H-κ stacking has been proposed.In application,for stations located above unconsolidated sediments and hard-rock sites which could be identified manually,the sequential H-κ stacking and single-layer H-κ stacking have been applied,respectively.This processing is relatively inefficient.To overcome the limitation,we extend the sequential H-κ stacking.Synthetic tests show that the improved sequential H-κ stacking can be used for both single-layer and two-layer crust models,and is applied for large datasets efficiently.Moreover,crustal layering has been investigated with the improved sequential H-κ stacking by using seismic data recorded from the regional permanent stations of the Sichuan basin and adjacent regions for 7 years,as well as from temporary stations deployed in the Weiyuan area.Our result shows that some stations in the central and northern Sichuan basin have a sediment thickness of 4.6~6.7 km,with average V_(P)/V_(S) ratios of about 1.9~2.9.The Conrad discontinuity is obvious beneath some stations in the southern Sichuan basin,with depths of 21~25 km.Thus it is estimated the upper crust thickness accounts for~56% of the entire crust.Crustal thickness varies across the two sides of the Longmenshan fault,and relatively high V_(P)/V_(S) ratios being located in the southern segment of this fault.

关 键 词：四川盆地 康拉德界面 改进的序贯H-κ叠加 接收函数 

分 类 号：P315[天文地球—地震学] P313[天文地球—固体地球物理学]