秦王川盆地西缘断裂活动性综合研究及盆地成因分析

秦王川盆地西缘断裂发育于陇中盆地地震构造区内部,本文对其进行了综合研究。浅层人工地震探测表明,该断裂在最小埋深130m处有显示,联合钻探结果表明该深度处为新近纪湖相沉积地层,泥岩层顶面向盆地方向呈斜坡状,槽探未揭露出断层。综合研究表明该断裂发育在新近纪地层内部,并未上穿第四纪沉积物,属于前第四纪隐伏断层。秦王川盆地在古近纪—新近纪山间泛湖盆的基础上,由于区域构造应力不均匀挤压抬升,形成山间负向地形,成为第四纪多变环境下河流堆积的拗陷盆地。秦王川盆地西缘断裂不具有控制中强地震空间分布的作用和形成地表破裂的能力,对盆地的构造稳定性不构成影响,亦不影响兰州新区的规划发展。

Comprehensive Study on Activity of the Western Margin Fault and Genesis Analysis of Qinwangchuan Basin

The western margin fault of Qinwangchuan basin can be regarded as interior fracture of the seismotectonic province of Longzhong basin.Taking the seismic microzoning of Lanzhou New Area as an opportunity,the authors made a comprehensive research on the western margin fault of Qinwangchuan basin.The results showed that in the 130m depth of the upper breakpoint of the fault is fonnd in the Neogene lacustrine strata by shallow seismic exploration and joint drilling,the roof of the mudstone trends in the direction of the Qinwangchuan basin too.The Baojiayao trench reveals no fault eviclerce near surface.Comprehensive research shows that the fault developed in the Neogene strata and did not cut upward the Quaternary sediments through.The western margin fault of Qinwangchuan basin is belongs to the buried fault of the former Quaternary.The Qinwangchuan basin was formed on the basic of the negative terrain among the mountains and had become a changeable fluvial-deposited depression basin in the Quaternary period,due to the regional tectonic stress differentiated compression and uplifting after the E-N intermountain Pan-lake Period environment.It could have no the function to control the spatial distribution of mid-strong earthquakes and the ability to form the surface rupture along the western margin fault of Qinwangchuan basin.Meanwhile,the tectonic stability of the Qinwangchuan basin and planning and development of Lanzhou New Area are not affected.