青东凹陷是渤海湾南部发育的一个新生代断陷盆地,其中出现了北西向、东西向和北北东向3组断裂系统.北西向和北北东向者属于基底断裂系统,分别是印支期前陆变形阶段形成的逆冲断层系和晚侏罗世形成的郯庐左行平移断层系.古近纪期间该凹陷在近南北向伸展应力作用下发生了强烈断陷活动,新生了近东西向的正断层系.两组基底断裂在此应力作用下复活并呈现为斜向拉张活动,北西向者具有左行平移分量,而北北东向者具有右行平移分量.青东凹陷内部以北西向基底断裂系统复活为主,早期活动强,控制形成了北西—南东向展布的沉积格局；晚期活动减弱或停止,被一系列新生东西向正断层所取代,并呈现为东西向的沉积格局.较大型的北西西向基底断裂由于其较低的强度和较为有利的拉张方位,表现为持续较强活动的特征.大型的北西向青东4断裂带和北北东向郯庐断裂带,虽处于不利的拉张方位,但由于其较低的强度仍表现为持续强烈的活动,分别在平面上出现了右阶状和左阶状雁列式断层组合,剖面上出现了似花状构造现象,显示了大型基底断裂的复活特征.通过对青东凹陷基底断裂复活方式的分析,可以将其分为直接复活的断层,派生雁列式断层、扩展和连接断层3类.由此可见,基底断裂对断陷盆地内断裂系统分布和演化以及沉积充填格局都具有十分重要的影响.%The Qingdong sag of the Jiyang depression is a Cenozoic faulted basin in the southern Bohai Bay basin. The sag contains nearly EW,NW and NNE striking fault systems. The NW and NNE striking faults belong to basement faults respectively resulting from foreland deformation in the Indosinian period and the Tancheng桳ujiang (Tan-Lu) sinistral faulting in Late Jurassic. The sag was under NS extension and undergone intense rifting during the Paleogene, leading to formation of the EW faults. The two sets of basement faults reactivated by a way of oblique extension under the NS extension. The NW and NNE striking basement faults have sinistral and dextral movement respectively. Reactivity of the NW striking basement faults predominate in the Qingdong sag during the Paleogene, which had more intensive activities and controlled the NW to SE sedimentary framework during the early rifting stage, then replaced by large numbers of EW faults and resultant EW sedimentary framework in the later rifting stage. However,the larger WNW striking faults with lower strength and in more favorable extended direction have the sustained and intensive activities. It is for the low strength that the large-scale Qingdong 4 fault zone and Tan-Lu fault zone also showed strong and sustained activities. Moreover, they present left or right en echelon arrangement on horizontal and flower liking structure on profile as being with large proportion of strike-slip movement,displaying the large-scale basement reactivated features. After more detail studies, reactivity patterns of the basement faults can be classed into three types, such as the direct activity, formation of new en echelon faults and direct activity plus propagating into EW faults. It can be seen that basement faults have important effect in the evolution and distribution of fault systems and sedimentary filling characteristic in a basin.
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