Study on Seismite Features and Its Time-Space Distribution Law of Paleogene in Liaodong Bay Depression

Key words: 
• Liaodong Bay depression /
• Paleogene /
• Tan-Lu fault /
• paleoseismic /
• seismites

Abstract: Many earthquake-related seismites were discovered in Paleogene in Liaodong Bay depression. According to the observation of well core, we identified 11 indicators of seismites of Paleogene in Liaodong Bay depression, including micro-fold, step micro-fault, seismic fall-masses, liquefied breccias, liquefied fold, pinch and swell structure, ball and pillow structure, flamy structure, liquefaction sandy-silty dyke, seismic-related fracture and seismic breccias. They all distribute in delt-front or the slope toe near prodelta. We establish the seismite succession through the degree of deformation. The seismites succession has been divided into I, II and III three units from weak to strong which reflect the intensity of Paleoseismic. Through the analysis of the seismites space-time distribution and its reflection on ancient earthquake intensity by geostatistical methods, we assume Tan-Lu Fault of Paleogene in Liaodong Bay depression was in the orientation of NNE. The tectonic activity can be divided into three stages. The first stage is E₂s³. The tectonic activity mainly distribute in the northern of Liaoxi Low salient. The second stage is E₃s²-E₃s¹. The tectonic activity mainly distribute in A oilfield of Liaozhong sag. The third stage is E₃d. The tectonic activity mainly distribute in A oilfield and the neighbouring area of Liaoxi Low salient, thinly distributed in the southern and northern of Liaozhong sag. The first and third stages are intense tectonic activity periods. The results show that through seismites time-space distribution to inverse the tectonic activity is feasible and it provides a new way of thinking for basin analysis.