Abstract: We have made field investigation and trench measurement along the piedmont fault of Daqingshan Mountain, Inner Mongolia, which is one of the most remarkable faults surrounding the Ordos block. The results show that the most recent time of activity is after Middle Holocene for the west section and before Late Holocene for the east section of the fault, respectively. The activity of the middle section of the fault during Holocene is characterized by integration. We have also analyzed the geomorphologic features, paleoearthquakes, surface ruptures caused by the Baotou earthquake of AD 849, and present day seismicity. It is suggested that there is a boundary of the fault near Tuzuq County, west of Huhehaute. The activity in Late Holocene of the fault was intensive on the west side of the boundary and not evident on the east side.

Key words: Mt. Daqingshan of Inner Mongolia, Piedmont active fault, Seismological surface rupture, Segmentation

摘要： 沿内蒙大青山山前活动断裂进行野外调查及探槽开挖的研究结果表明,该断裂西部地段及东部地段的最新活动时期在全新世中期以后及全新世晚期以前;中部地段在全新世晚期强烈活动,公元849年包头地震的地表破裂沿该段展布。大青山山前台地与断层陡坎分布、洪积扇类型及河流阶地断错等地貌特征、全新世晚期断裂活动范围、沿断裂带探槽开挖获得的古地震事件对比,以及现今中小地震震中分布表明,全新世晚期大青山山前断裂的活动以土左旗为界,该界以西全新世晚期断裂强烈活动,该界以东全新世晚期断裂活动不明显。全新世时期大青山山前断裂的活动显示了由东向西的迁移。

关键词: 内蒙大青山, 山前活动断裂, 地震破裂, 分段