天津—北京高分辨地震折射剖面初至波走时成像

Tomography of High Resolution Seismic Refraction Traveltimes in Tianjin-Beijing Profile

利用走时成像中的正则化反演方法对天津—北京的高分辨地震折射剖面获得的初至波资料进行成像。分析了不同的初始模型和参数变化对反演结果的影响,并采用检测板方法对最终模型的分辨进行评估,得到了天津-北京剖面的上地壳精细速度结构,给出了该地区的隐伏断层。结果显示,最终模型分辨达到5km×1km,部分地区更加细致;研究区域坳陷区与隆起区相间,大坳陷内部有小坳陷;结晶基底的深度变化约2～8km,其起伏形态符合地质构造情况;断裂活动和第三系以来的壳内运动对速度结构影响较大。

The traveltimes tomography of first arrive waves along Tianjin-Beijing profile with high resolution is done using regularization inversion method.The impacts on the inversion results from very different starting models and inversion parameters are analyzed,the resolution of the final model is assessed by the checkboard method,and the upper crust fine structure with blind faults in the study area is obtained finally.The results show that the resolution of the final model is up to 5 km×1 km with some are more fine.The study region is alternate by depressed areas with upheaval areas,and small sags are within big ones.The depths of crystalline basement change in the range of 2-8 km and its fluctuant pattern complies with the geological tectonic characteristics.The fault activity and crustal moment since Tertiary have greater impact on the velocity structure of this region.