应用层析成像技术研究华北地壳速度结构

Application of tomography to the studies of crustal structure in North China

利用华北地区１６９ 个地震台站记录的１９８４～１９９５ 年的１ ６９６ 个地震的Ｐ波到时资料，重建了华北地区地壳三维速度图像。不同深度的速度图像表明： 地壳中地震波速度的横向不均匀性显著， 上地壳的速度分布与地表已知构造特征相联系； 太行山山前断裂带是切割到地壳底部的深断裂带； ２５ ｋｍ 深度普遍存在速度间断面； 地壳底部起伏明显； 强震孕育发生与其周围介质的不均匀性和上地幔的隆起或凹陷密切相关。

In this paper,the three dimensional velocity images beneath the North China are reconstructed by using P wave travel time data of regional earthquake recorded by the North China seismic network.The main results are as follows:(1)The velocity images display clearly the lateral heterogeneity in siesmic velocity in North China and The velocity distribution of upper crust are correlated to the surficial geological features.(2)The Taihang Mt.Piedmont fault zone can be traced down to the bottom of crust.(3)The velocity discontinuity surface generally exist at the depth of 25 km.(4)The crust mantle boundary is obviously undulated.(5)Development and occurrence of strong earthquakes have close relationship to the lateral heterogeneity in wave velocity and the upheaval or hollow of uppermost mantle.