A DETACHMENT REVEALED BY DEEP SEISMIC-REFLECTION PROFILING IN JIZHONGDEPRESSION

North China basin is a large-scale Cenozoic rifted basin in eastern Ch ina. It was a stable continental block before Mesozoic, and experience d several significant stages of faulting and subsiding during Cenozoic . Many studies[1, 2] have shown that the extensional structures of Nor th China basin are similar to those of Basin and Range in the U.S.: Th e basin consists of a series of grabens and horsts; most of the faulte d basins are half-graben with a high or low angle planar normal fault (or a listric fault) on one side, and a sedimentary overlap on the oth er. This important conclusion comes from the seismic reflection profil ing for oil exploration. However, the reflection profile in this area just displays the processed results within TWT 4 s, and gives little d eterministic evidence for the important structure (e.g. the detachment ) below 4 s in North China. Thus, the analysis of the bottom of the up per crust and of the mid-lower crust only resorts to other deep geophy sical methods. But they are inferior to the reflection profiling metho d in the way of resolution; thus further probing to some key problems is hindered. Based on the deep seismic reflection profile completed re cently, the detachment in Jizhong depression is emphatically discussed in this note.