长白山火山区地壳S波速度结构的背景噪声成像

摘要

利用探测深俯冲的中国东北地震台阵NECsaids的60个流动台与固定地震台2010年7月至2014年12月的垂向连续波形数据,采用地震背景噪声成像方法获得了研究区6～40 s周期的瑞雷波相速度分布,并通过相速度频散反演得到了研究区下方0～50 krn的三维S波速度结构.结果表明:研究区下方地壳S波速度结构存在明显的横向和纵向不均匀性,浅部速度结构与浅表地质构造单元有较好的对应,深部速度结构较好地反映了区域火山活动及深部热物质作用的结构特征;在长白山火山下方9～30 km深度范围内存在明显低速区并有向下延伸的趋势,推测可能为长白山火山地壳岩浆囊;在龙岗火山下方12～30 km深度范围内发现较弱的低速区,可能代表火山喷发后的残留物,而在镜泊湖火山下方没有明显的低速异常,说明镜泊湖火山地壳内可能不存在部分熔融的岩浆物质.%The vertical component of continuous data recorded by the temporary NECsaids array and regional permanent broadband seismic stations from July 2010 to December 2014 in the deep subduction zone in northeast China are used to obtain the Rayleigh wave phase velocity maps at periods 6～40 s in the study area,then the Rayleigh wave phase velocity dispersions are inverted to determine 1-D shear wave velocity and assembled into a 3-D model of depth 0～50 km.The results show that the S wave velocity structure of the crust has lateral and vertical heterogeneity,the velocity structure of shallow crust is well related with the tectonic units on the surface,and the deep structure reveals the volcanism and regional deep thermal erosion effect.The low velocity anomaly bodies are found at depth of 9 ～ 30 km beneath the Changbaishan volcano and have a tendency to extend deeper,which may be the magma chamber in crust of the Changbaishan volcano.There is also a weak low velocity anomaly body at depth of 12～30 km beneath the Longgang volcano,which may be the remains after eruption,and no obvious low velocity anomaly body beneath the Jingpohu volcano,which means that there is no partial melting magma in the crust below it.