唐海—商都地震台阵剖面下方岩石圈结构

2006年10月到2009年9月,中国地震局地球物理研究所在华北地区布设了250个流动地震台站,本文选取其中一条从唐海经过唐山、三河、北京、张家口到商都的宽频带地震台阵剖面作为研究对象.利用该剖面49个宽频带台站记录的191个远震数据进行了S波接收函数的计算,通过共转换点叠加成像对剖面下方的岩石圈结构进行研究,获得了剖面下方的岩石圈精细结构.Moho界面和岩石圈-软流圈界面清晰可见,剖面下方地壳厚度从西到东逐渐减薄,从42 km逐渐减薄至30 km左右,西部陆块岩石圈厚度从100 km逐渐减薄至70 km,中部和东部陆块岩石圈厚度变化相对平稳,介于60~80 km,表明剖面下方岩石圈遭受了大规模的明显减薄.结合其他地球物理方法研究结果,我们认为剖面下方华北克拉通东部陆块岩石圈减薄主要是由于热侵蚀作用引起的.

Lithospheric structure beneath Tanghai-Shangdu seismic profile

A temporary seismic array was established by Institute of Geophysics, China Earthquake Administration in North China from Oct. 2006 to Sep. 2009 using 250 portable broadband instruments. We chose a profile inside the array, from Tanghai through Sanhe, Beijing, Zhangjiakou to Shangdu, to study the lithospheric structure beneath North China. We used 191 teleseismic events recorded by 49 stations to calculate S receiver functions, and then used the common conversion point stacking method to obtain a detailed lithospheric structure beneath the profile. The Moho and lithosphere-asthenosphere boundary (LAB) were imaged clearly. The crustal thickness decreases from west to east along the profile, it decreases from 42 km to 30 km. The lithospheric thickness decreases from 100 km to 70 km in the western part of North China Craton and varies from 60 km to 80 km beneath the central part and eastern part of North China Craton. The results show that the lithosphere experienced significant amount of thinning. Combined with the other geophysical results, we suggest that the thermal erosion caused the thinning of the lithosphere beneath the eastern part of North China Craton.