大陆地壳岩石结构重建：方法与实例

The composition of the continental crust has long been a subject of interest to earth scientists as it can provide key information about the crustal growth and evolution of the continents. In this paper we make a comparative study on the lithological discrimination schemes featuring with the use of different seismic attributes, such as P-wave velocity, P- to S-wave velocity ratio, acoustic or elastic impedances, Lame impedances and high-sensitive identification factors. The results demonstrate that Lame impedances have more powerful constrains than other seismic attributes. In order to fully take the advantage of make the best of the different seismic response of crustal rock, we firstly use seismic attribute that have weak distinguish power to construct loose constrained lithological model, then use seismic attributes that have stronger distinguish power to tighten the constrains of lithological discrimination. We propose a joint scheme (chain constrain technique) by combing all available constrains to reduce the non-uniqueness in mapping rock distribution. We adopt chain constrain technique to construct lithological model beneath Tunxi-Wenzhou transect, Southeastern China, Manzhouli-Suifenhe transect, Northeastern China, and geophysical profile in Bohai Bay Basin, North China. The results can be suumarized as the follows: (1) We compare the sensitivity of different seismic factor constraints on rock types, and conclude that Lame impedances have tighter constrains than seismic velocity, Vp/Vs, density. (2) We propose chain constrains to construct lithological model from integrated geophysical data, and reduce the non-uniqueness in mapping rock distribution. (3) We reconstruct crustal lithological model beneath Tunxi-Wenzhou transect, Southeastern China. The results suggested that Jiangshan-Shaoxing fault is a crust-scale, and it is the boundary between Cathaysia and Yanthze blocks. (4) We construct crustal lithological model beneath Manzhouli-Suifenhe transect, Northeastern China. (5) We map the petrologic distribution along a geophysical profile in Bohai Bay Basin, North China, and construct a three-layered petrology model from the depth 2 km to about 10 km, consisted of basalt (the first layer), pelitic siltstone (the second layer), and silty mudstone and fine sandstone (the third layer).