【摘要】 利用华北地区大型流动地震台阵的记录资料,采用近震和远震联合成像方法,得到了水平分辨率0.5°×0.5°、深至600km的S波速度结构.研究结果表明,上地壳S波速度结构与地表地质构造基本一致,燕山—太行山山脉均呈现高速异常,延庆—怀来盆地、大同盆地表现为低速异常,华北盆地内部的拗陷和隆起分别呈现低速和高速.唐山地区中地壳、山西裂陷盆地中下地壳存在明显的低速异常,可能分别与流体和热物质作用有关,有利于形成孕育强震的地质构造环境.90km的速度结构图像依然与地表的构造特征有较大的相关性,可能说明深部结构对地表构造有一定的控制作用.燕山隆起区岩石圈的厚度可达120～150km左右,华北盆地的岩石圈厚度可能在80km左右,太行山地区的岩石圈厚度介于两者之间.山西裂陷盆地上地幔低速层较厚,反映了该区不稳定的构造环境造成了地幔热物质的上涌.华北盆地下方220～320km出现的高速异常体,可能揭示了华北盆地上地幔仍然存在拆沉后残留的难熔、高密度的古老岩石圈地幔.研究区东部地幔转换带呈低速异常,推测可能与太平洋板块俯冲至该区下方地幔转换带前缘120°E左右的俯冲板块相变脱水有关.更多还原

【Abstract】 We obtained 3-D S-wave velocity structure with the horizontal resolution of 0.5°×0.5° and down to 600km depth by jointly inverting local and teleseismic events recorded by the North China Seismic Array.Our results show that S-wave velocity anomalies in the upper crust agree well with surface geological features.High S-wave velocity anomalies are shown in Yanshan and Taihangshan uplift,while low S-wave velocity anomalies are shown in Yanqing-Huailai basin and Datong basin.Besides,low and high S-wave velocity anomalies are imaged in Depression and uplift of North China basin,respectively.Distinct low S-wave velocity anomalies are shown in Tangshan region and the surrounding areas in the middle crust,which may be caused by fluids,and low velocity anomalies are shown in Shanxi rift basin in the middle and lower crust,which may be caused by hot materials,thus easily to form the seimogenic environment.S-wave velocity structure at 90km depth still shares the similarity with surface geological features,indicating that deep structures have influence on the velocity structure.The thickness of lithosphere beneath Yanshan uplift is thicker than that of Taihangshan uplift,which may reach the depth of 120～150km,while in North China basin may reach the depth of 80km.A wide range of low velocity anomalies are imaged in the upper mantle beneath Shanxi rift basin,which may be related to the upwelling materials from mantle.High velocity anomalies beneath North China in the depth of 220～320km may due to the detached Archaean continental lithosphere.Low velocity anomalies in the mantle transition zone of eastside of the study area may be related to dehydration of the subduction of the Pacific slab in the mantle transition zone at the edge of 120°E.更多还原