| 怀安盆地北缘断裂中段晚第四纪活动性研究 |
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| 关键词:Huai’an basin fault activity slip rate paleoearthquake Quaternary |
| 基金项目:国家重点研发计划“300 m级特高坝抗震安全评价与控制关键技术”项目“坝址地震动输入研究”专题(编号: 2017YFC0404901);地震行业科研专项“中国地震活断层探察——华北构造区”项目(编号: 200908001) |
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| Research on Quaternary Activity of the Middle Segment of Northern Margin Fault of Huai’an Basin, Hebei Province |
| Located in Zhangjiakou area of Hebei Province, Huai’an basin is one of the active basins that lie in Shanxi–Hebei–Mongolia Basin-Range tectonic area. On the northern margin of the basin there is an active fault, named northern margin fault of Huai’an basin, which has been controlling the basin’s development. To study the activity of the middle segment of the fault the authors excavated three trenches. The first trench (TC-1) was excavated on the lowest pluvial fan of a gully, the second (TC-2) on the second pluvial fan, and the third (TC-3) on the lowest pluvial fan of another gully. TC-1 shows that the overburden layers (about 12 m thick) covering the fault are not offset by the fault. TC-2 reveals that the fault is composed of several secondary faults which offset most layers. The displacement increases with the depth. TC-3 shows similar features to TC-2. Through surveying, mapping, sampling and dating about the trenches, some activity parameters of the fault was obtained. The latest active period of the fault segment was Late Pleistocene. The average slip rate during the Late Pleistocene was about 0.12 mm/a. At least 3 paleoearthquakes were recognized at TC-2 and TC-3, and the last two took place about 40 ka BP and 28 ka BP respectively with an average coseismic displacement of 1.3 m. The average earthquake recurrence period was about 11 ka. The fault segment has the ability to generate MS 7 earthquake, and close attention should be paid to its earthquake risk since the last producing-surface-rupture earthquake has elapsed for more than 20 ka. |
| CHEN Wen-bin,SONG Yi-sheng,LI Xiao-jun,PAN Hua,LI Jin-chen.2019.Research on Quaternary Activity of the Middle Segment of Northern Margin Fault of Huai’an Basin, Hebei Province[J].Acta Geoscientica Sinica,40(6):827-835. |
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