The Development Characteristics Of Exensional-shear Fault System Of Linnan Area

Shear structure is very common crust horizontal movement, in the east of China lots of shear structure have been accomopanied with continental fauled basins because of Tanlu fault and other large-scale shear faults, and the typical extensional-shear fault system develop regularly in Linnan area of Shengli. Owing to the multi-episodic tectonism, Linnan area has complicated structure, strong activities of fault, diversified structural pattern. The oil and gas exploration have been restricted to a great extent in this area, as a result of lacking higher precision and dynamic analysis to fault development, and clear study of genetic mechanism.The paper base on identifying and explaining extensional-shear fault systerm, and combine the seismic cross-section with horizontal section, which identify precisely the extensional-shear fault in Linnan area; and in order to know the feature of externsional-shear fault, we take advantage of data of earthquake, logging, well drilling and areal geology, and analyse characteristics of geometric tectonic as follow: sinngle fault–fault systerm–sturcture unit; through the analysis of the motiliny of faults and recovering equilibrium profile, the tectonics of the development to externsional-shear fault will be studied quantitatively and dynamically; the feature of the stress field and the its time-space distributing disciplines have been conformed by the analysis of geology and the dinite element method numerical simulating technology. What's more , the mechanism of externsional-shear fault systerm has been studied which base on the background of area geology.The major pattern combination of faults in Linnan area is"broom-type"in the plane, and"double break","multistep Y","negative flower"in section, which appear the feature of externsional-shear fault, and the domaining structural pattern are externsional and shear pattern; the externsional-shear fault in Linnan area formed in the third member of Shahejie Period, the two reversed broom-type fault zone of Linshang and Xiaokou determine the tectonic pattern of the whole area, and the activity reach a pinnacle in the third member of Shahejie Period, Dongying Period and Minghuazhen Period; The tectonic development in Huiming sag experienced the formation of the half garben in the north side and an overlop in the south side in Kongdian period; then the shinking of the half graben in the fourth member of Shahejie Period; then the formation of graben or horst in Dongying Period and the third member of Shahejie Period, the forming of depression in Guantao Period and Minghuazhen period; From the third member of Shahejie Period to Minghuazhen Period, tensile stress and shearing stress decrease gradually, and the derection of tensile stress change NNW to NNE, and the shearing stress lager than the tensile stress in these times; Earth's mantle upwell in Paleogene, and the horizontal intensive stretching induce the regional faults, at the same time, the NNE-SSE tensile stress and the NEE-SWW dextral shear stress is formed by the dextral strike-slip activtiy of Tanlun faults, and Linnan area pivots on Luxi uplift, which form the"broom-type"tectonic systerm.