利用接收函数研究河套裂谷系西段及周边区域地壳结构  

Crustal structure around the western Hetao rift and adjacent area revealed by receiver functions

作　　者：刘嘉栋 吴庆举[1,2] 朱敏 LIU Jiadong;WU Qingju;ZHU Min(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Key Laboratory of Earthquake Source Physics,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 [2]中国地震局震源物理实验室,北京100081

出　　处：《地质学报》2025年第1期293-305,共13页Acta Geologica Sinica

基　　金：国家自然科学基金重点项目(编号42030310);国家自然科学基金青年基金项目(编号42404116)联合资助的成果。

摘　　要：位于河套裂谷系西段的临河坳陷和狼山隆起,是环鄂尔多斯裂谷系和阴山造山带的重要组成部分,其地壳结构对于认识河套裂谷系和阴山造山带的形成机制具有重要意义。目前对于该区域地壳结构已有一些认识,但仍然存在争议,较为重要的是临河坳陷地壳是否增厚。本文基于临河坳陷和狼山隆起及周边布设的118个宽频带地震观测台阵数据,提取远震P波接收函数,探究了研究区的地壳结构信息。利用沉积层基底转换波时间延时获得了研究区沉积层厚度,结果显示临河坳陷规模较大,新生界地层平均厚约5.3 km,查干德勒苏坳陷规模较小,沉积层平均厚度2.7 km。H-κ叠加得到的狼山山前断裂带以北区域波速比相对较低,平均值约1.75,推断该区域地壳岩石组分以长英质为主。H-κ叠加得到的地壳厚度和共转换点(CCP)叠加成像得到的莫霍面埋深较为一致,表现为狼山隆起莫霍面较深西北侧较浅的特征。结合狼山隆起相对较低的波速比,本文推断狼山隆起受南北向挤压导致上地壳增厚是隆起造山的主要原因。本文得到的临河坳陷莫霍面轻微上隆,推断临河坳陷地壳在拉张环境下受地幔物质上涌影响发生减薄。本研究的结果对探索河套裂谷系和阴山造山带的形成机制提供了一定的约束。The Linhe rift and Langshan uplift,located in the western section of the Hetao rift system,are important parts of both the Ordos rift system and the Yinshan orogenic belt.The crustal structure in this region is of great importance for unraveling the geodynamic processes responsible for the formation of both the Hetao rift system and the Yinshan orogenic belt.However,aspects of this crustal structure,such as the crustal thickness of the Linhe rift,remain a subject of debate.This study analyzes teleseismic waveforms from 118 broadband seismic stations deployed across the western Hetao rift and adjacent areas.P-wave receiver functions are calculated to obtain information about the crustal structure.Time delays of the sediment-converted Ps phase are employed to determine the thickness of Cenozoic and overlying sedimentary layers.Our results indicate an average sedimentary thickness of approximately 5.3 km in the Linhe rift,compared to about 2.7 km in the Chagandelesu rift.H-κstacking reveals a relatively low crustal VP/VS ratio of 1.75,suggesting a predominantly felsic composition in the crust northwest of the Langshan piedmont fault.Besides,crustal thickness obtained from H-κstacking is consistent with Moho depths derived from CCP stacking,showing a deeper Moho beneath the Langshan uplift and a shallower one on the northwest side.Combined with the relatively low VP/VS ratio beneath the Langshan uplift,it is inferred that the uplift is primarily caused by upper crustal thickening under north-south compression.In contrast to previous findings,this study identifies a slight Moho uplift beneath the Linhe rift,suggesting crustal thinning occurred under extensional conditions and may be influenced by mantle upwelling.These new insights constrain the formation mechanisms of the Hetao rift system and the Yinshan orogenic belt.

关 键 词：临河坳陷 狼山隆起 接收函数 地壳厚度 波速比 

分 类 号：P548[天文地球—构造地质学]