摘要
大同火山区是华北克拉通最大的第四纪板内火山群,自中生代以来经历了强烈的构造变形和岩浆活动,多期次的喷发活动造成地表火山锥分布广泛,然而火山区浅部的岩浆通道分布特征却尚不清楚.本研究利用部署于大同火山区123个短周期地震仪台站的波形资料,采用背景噪声层析成像方法得到火山区浅部(<2 km)精细的三维S波速度模型;进一步,基于水平与垂直谱比法(Horizontal-to-Vertical Spectral Ratio,HVSR)和远震相对走时残差获得火山区沉积层的整体分布特征.研究结果表明,火山区浅部速度结构存在明显的横向不均匀性,低速异常被相对高速的物质分割为三个主要区域,且在火山锥分布较为密集的区域其S波速度表现为低速异常;同时,三维速度模型显示在不同火山锥下方低速异常的幅值及延伸范围差异明显,暗示了不同的岩浆喷发通道;另外,基于HVSR曲线的峰值频率也揭示出火山区下方隆起的结构特征.为此,本文提出大同火山区存在西侧、中间和东侧三个火山喷发通道,结合前人上地幔和地壳的速度结构,以及不同位置火山的喷发时间,本研究构建了大同火山区从深部至浅地表更为精细的结构模型,其中幔源熔体向上侵入在中地壳形成低熔融度的岩浆房,而多期次阶段性的喷发活动则在浅地表形成了三个岩浆运移通道.
The Datong Volcanic Zone(DVZ),the largest Quaternary intraplate volcanic cluster in the North China Craton,has undergone significant tectonic deformation and episodic magmatism since the Mesozoic,resulting in widespread volcanic cone distribution across multiple eruption phases.However,the distribution of shallow magma channels in the DVZ remains poorly understood.This study utilizes waveform data from 123 short-period seismometers deployed across the DVZ and employs ambient noise tomography to construct a highresolution three-dimensional S-wave velocity model of the shallow crust(<2 km).Furthermore,the Horizontalto-Vertical Spectral Ratio(HVSR)method and teleseismic relative travel-time residuals were used to characterize the sedimentary layer's distribution.The results indicate significant lateral heterogeneity in the shallow velocity structure,with low-velocity anomalies segmented into three primary zones by relatively highvelocity materials.Notably,regions with densely distributed volcanic cones exhibit pronounced low S-wave velocities.The three-dimensional velocity model reveals distinct variations in the amplitude and spatial extent of low-velocity anomalies beneath different volcanic cones,suggesting the presence of separate magma eruption channels.Additionally,the peak frequencies of the HVSR curves provide insights into the structural characteristics of the uplifted basement beneath the DVZ.Based on these findings,this study proposes the existence of three volcanic eruption channels in the DVZ:western,central,and eastern.By integrating previous research on upper mantle and crustal velocity structures,as well as the eruption chronology of volcanoes at different locations,a refined structural model of the DVZ is constructed,spanning from depth to the surface.This model suggests that mantle-derived melts intrude upward to form a magma chamber with a low degree of melting in the middle crust,while multi-phase episodic eruptions have established three magma migration channels in the shallow subsurface.
作者
王肖薇
张广伟
何静
吉宇
任俊杰
胡幸平
WANG XiaoWei;ZHANG GuangWei;HE Jing;JI Yu;REN JunJie;Hu XingPing(National Institute of Nature Hazards,Ministry of Emergency Management of China,Beijing 100085,China;School of Safety Engineering,China University of Mining and Technology,Xuzhou Jiangsu 221116,China;State Key Laboratory of Deep Eath Exploration and lmaging,School of Earth Science and Resources,China University of Geosciences,Beijing 100083,China)
出处
《地球物理学报》
北大核心
2025年第12期4652-4668,共17页
Chinese Journal of Geophysics
基金
国家自然科学基金项目(U2139201,42474095,42004042)
大同市区活动断层探测与地震危险性评价项目共同资助。
关键词
大同火山
背景噪声成像
HVSR
三维速度模型
岩浆通道
Datong volcano
Ambient noise tomography
HVSR
Three-dimensional velocity structure
Magma channel
