北京顺义断裂第四纪活动性地球物理及钻孔综合探测证据

Application of comprehensive geophysical-drilling exploration to detect the buried Shunyi active fault belt in Beijing

顺义断裂是北京平原区重要的隐伏断裂之一,其第四纪活动性及其对地表地裂缝地质灾害影响的研究是优化首都地区国土空间开发格局和防灾减灾体系建设的必要工作。针对隐伏断裂的复杂性特征,利用可控源音频大地电磁测深(CSAMT)、浅层人工地震、高密度电阻率法地球物理探测,以及钻孔地层剖面记录等方法,综合分析顺义断裂第四纪活动特征,结果表明:①顺义断裂走向NE,倾向SE,正断活动特征,为全新世活动断裂,北小营附近断裂上下盘早更新世、中更新世、晚更新世和全新世以来的垂直滑动速率分别为0.23mm/a、0.03 mm/a、0.29 mm/a和0.51 mm/a;②断裂第四纪以来时空存在明显差异,时间上,早更新世断裂活动性较强,中更新世活动弱,晚更新世活动性增强,全新世以来活动性最强,空间上,第四纪以来顺义断裂南段的活动性较北段强;③顺义断裂现今仍具有一定蠕滑活动特征,并对浅地表部地裂缝发育具有明显的控制作用,这可能是顺义地裂缝发育的主要原因。

Shunyi fault is one of important buried faults in the Beijing plain. The Quaternary activity and ground deformation of this fault are important for optimizing the pattern of land space development, and constructing disaster prevention and mitigation plans in Beijing. Since the buried active fault is complex, we used controlled source audio-frequency magnetotelluric(CSAMT), shallow seismic reflection, high density resistivity and drilling exploration to detect its location, character and activity intensity. The results show that the Shunyi fault trends NE, dips to the SE, and is a normal fault. The Shunyi fault is an active fault with variable activity: its vertical activity rate was 0.23 mm/a since the Early Pleistocene, 0.03 mm/a since the Mid-Pleistocene, 0.29 mm/a since the Late Pleistocene, and 0.51 mm/a since the Holocene in the Beixiaoying town. There were spatial and temporal disparities in the Shunyi fault activity since the Quaternary. It was strongly active in the Early Pleistocene but showed weaker activity during the Middle Pleistocene. In the Late Pleistocene, the activity of Shunyi fault was enhanced, and the strongest activity occurred in the Holocene. It’s worth noting that the south segment of Shunyi fault had stronger activity than north segment since the Quaternary, and is still active, which may explain why the ground fissures appeared in Shunyi recently. Obviously, active faults control ground fissures in Shunyi area.