海南琼北火山区上地壳岩浆囊的地震背景噪声成像研究  

Crustal magma chamber beneath the Qiongbei volcano field in Hainan Island unveiled by seismic ambient noise tomography

作　　者：陈凯琪 李志伟 林建民 包丰 夏鑫 夏少红[6] 蔺文静[7] 甘浩男 王嘹亮[8] 涂广红 王鹤 CHEN KaiQi;LI ZhiWei;LIN JianMin;BAO Feng;XIA Xin;XIA ShaoHong;LIN WenJing;GAN HaoNan;WANG LiaoLiang;TU GuangHong;WANG He(School of Marine Science and Technology,Zhejiang Ocean University,Zhoushan 316022,China;Beijing Institute of Spacecraft Environment Engineering,Beijing 100094,China;Ocean College,Zhejiang University,Zhoushan 316021,China;Innovation Academy for Precision Measurement Science and Technology,Chinese Academy of Sciences,Wuhan 430077,China;Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou 510301,China;Institute of Hydrogeology and Environmental Geology,Chinese Academy of Geological Sciences,Shijiazhuang 050061,China;Guangzhou Marine Geological Survey,China Geological Survey,Guangzhou 510301,China;Heilongjiang Hydrogeology Engineering Geological Survey Institute,Harbin 150030,China)

机构地区：[1]浙江海洋大学海洋科学与技术学院,舟山316022 [2]北京卫星环境工程研究所,北京100094 [3]浙江大学海洋学院,舟山316021 [4]中国科学院精密测量科学与技术创新研究院,武汉430077 [5]中国科学院地质与地球物理研究所,北京100029 [6]中国科学院南海海洋研究所,广州510301 [7]中国地质科学院水文地质环境地质研究所,石家庄050061 [8]中国地质调查局广州海洋地质调查局,广州510301 [9]黑龙江水文地质工程地质勘察院,哈尔滨150030

出　　处：《地球物理学进展》2022年第4期1379-1391,共13页Progress in Geophysics

基　　金：国家重点研发计划(2018YFC1504202);国家自然科学基金(41874046,41674065,41741018,41974064);中国-东盟海洋地学研究与减灾计划(121201002000150022);中国地调局地质调查项目(DD20160191)联合资助。

摘　　要：本文利用位于海南、广西、广东等地区32个固定地震台站的背景噪声连续波形数据,基于波形互相关提取得到了Rayleigh波5~22 s的群速度频散曲线和6~11 s的相速度频散曲线,采用0.25°×0.25°的网格划分完成了面波层析成像.利用群速度和相速度频散曲线联合反演获得了海南岛及周边区域至25 km深度的三维S波速度结构.基于反演获得的三维S波速度结构模型,正演计算得到了不同周期的Rayleigh波群速度、相速度异常分布,并与面波层析成像的结果进行对比.结果表明:不同周期面波成像结果比较一致,大部分地区的差值小于0.04 km/s(约1%),表明本文反演得到的三维S波速度结构模型可以解释观测数据.本文研究发现:海南琼北地区地表至15 km深度存在显著的低速异常;5 km以上深度的低速异常可能是火山喷发后的裂隙内流体填充造成的;至于5~15 km深度,存在更加显著的低速异常,低值异常幅度低于-10%甚至更低,推测可能存在部分熔融的上地壳岩浆囊.基于S波速度低值异常与岩浆囊熔融百分比定量关系的研究结果,使用6~16 km深度的S波低速异常模型,本文计算得到的最大熔融百分比约为25%,岩浆囊熔融部分的体积约为340 km^(3).限于本文缺乏更长周期的面波数据,尚无法对更大深度的S波速度结构进行良好约束,因此对于海南琼北火山区20 km以下深度是否存在更大尺度岩浆囊尚需进一步研究。We collected the continuous seismic ambient noise data of 32 permanent stations located in the Hainan Island,Guangxi Province,and Guangdong Province.The data are recorded about two years from 2014.We extracted the Rayleigh wave dispersion curves with the group velocity from 5 s to 22 s period and the phase velocity from 6 s to 11 s period based on the crosscorrelation functions,then obtained the ambient noise tomography on a 0.25°×0.25°grid.At the same time,the 3D Swave velocity structure up to the depth of 25 km was derived based on the joint inversion of group and phase velocity dispersion data.Then we estimated the anomaly distribution of Rayleigh wave group velocity and phase velocity in different periods based on 3D Swave velocity structure model and compared it with the results of the surface wave tomography.The results show that the imaging results of different periodic surface waves have little change.In most regions,the difference is less than 0.04 km/s(about 1%),indicating the 3D Swave velocity structure model could explain the observed data well.In addition,we found that there is a significant low velocity anomaly from the surface to a depth of 15 km in the region of Qiongbei.We speculate that the low velocity anomaly at a depth above 5 km may be caused by fluid filling in the fissure after volcanic eruption.As for the depth of 5~15 km,there is a more significant low velocity anomaly,and the low value anomaly is less than-10%or even lower.We propose that there may be a partially melted upper crust magma chamber.Based on the results of the quantitative relationship between the low velocity Swave anomaly and the melting percentage of magma chamber,we calculated the maximum percentage is about 25%and the molten volume is about 340 km^(3) using the low velocity anomaly model whit a depth of 6 to 16 km.Due to the lack of longer period surface wave data,it is not yet possible to constrain the Swave velocity structure of a larger depth.Therefore,whether there is a larger scale magma chamb

关 键 词：地震背景噪声 层析成像 低速异常 火山岩浆囊 

分 类 号：P315[天文地球—地震学]