深井盆地南缘断裂特征与活动性研究

Characteristics of Quaternary Activities of the Southern Margin Fault of the Shenjing Basin,Hebei Province

深井盆地是山西断陷盆地带北段内部一个规模很小的次级盆地,为中更新世以来发育的三角型山间小型盆地。盆地附近断裂发育,构造复杂,深井盆地南缘断裂为主控边界断裂,控制着盆地的发展演化。本文通过对地形地貌、断裂剖面、地层测年及地震活动等方面的分析和研究,获得了断裂活动时代和活动速率等参数,综合阐述了断裂的空间展布及活动特征。研究表明:深井盆地南缘断裂晚第四纪期间仍在活动,最新活动时代为晚更新世晚期;断裂具有分段性,西段长约6km,多处可见断裂错断晚更新世地层剖面,属正断倾滑性质;东段表现为盆地与黄土斜坡直接接触,由西向东断裂地貌表现逐渐减弱,未见明显的断裂剖面,止于NW向构造,附近发生的4次4 3/4级地震与该段断裂关系密切。

The Shenjing basin is a small-scale secondary basin in the Shanxi fault basin system, which is surrounded by bedrock mountain and is separated from other secondary basins. There are many faults around the basin, the south margin fault of Shenjing basin, as the main boundary fault, played the important role in the evolution and development of the basin. In this paper, we analyzed and studied the topography, fracture profile, strata dating and seismic activities of the fault, as well as the spatial distribution and activity characteristics of the fault. Our research shows that the fault on the south margin of Shenjing basin was active during Quaternary. The latest active period of the fault is in the late Pleistocene, which is characterized with segmentation. The west segment is about 6km long with many late Pleistocene stratigraphic sections in normal dip slip nature. The east segment shows basin direct contact with loess slope. From west to east, the tectonic behavior of landform gradual weakening to end at the old NW structure. The occurrence of 4 earthquake with Ms4 3/4 near the fault is closely related to the NE trending fault structure.