| 怀安盆地北缘断裂中段晚第四纪活动性研究 |
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| 引用本文：陈文彬,宋毅盛,李小军,潘华,李金臣.2019.怀安盆地北缘断裂中段晚第四纪活动性研究[J].地球学报,40(6):827-835. |
| DOI：10.3975/cagsb.2019.071001 |
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| 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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| 中文摘要:怀安盆地位于河北省张家口, 是晋冀蒙盆岭构造区的活动构造盆地之一, 在其北缘发育了控制盆地的怀安盆地北缘断裂。为了研究断裂的活动性, 在断裂中段开挖了3个探槽, TC-1位于一条冲沟的一级洪积扇上, TC-2位于二级洪积扇上, TC-3位于另一条冲沟的一级洪积扇上。TC-1揭示断裂没有断错厚度约12 m的覆盖层; TC-2揭示出由多条次级断层组成的断裂, 断裂断错了大部分层位, 且位错量随深度加大; TC-3剖面特征与TC-2相似。通过对探槽剖面进行详细的分析、测绘、描述和取样测年, 得到了有关断裂的活动性的参数。分析表明, 怀安盆地北缘断裂中段的最新活动时代为晚更新世晚期, 晚更新世的平均滑动速率为 0.12 mm/a。TC-2和TC-3探槽显示断裂曾有过多次活动, 并可识别出至少3次地表破裂型的古地震事件, 其中最后2次分别发生于距今约40 000 a和距今约28 000 a, 平均同震垂直位移为1.3 m, 断裂的平均地震重复间隔约为11 ka。断裂具有发生7级地震的能力, 末次地表破裂型地震的离逝时间已超过20 ka, 对其危险性应予以重视。 |
| 中文关键词:怀安盆地 断裂活动性 滑动速率 古地震 第四纪 |
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| Research on Quaternary Activity of the Middle Segment of Northern Margin Fault of Huai’an Basin, Hebei Province |
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| Abstract: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. |
| keywords:Huai’an basin fault activity slip rate paleoearthquake Quaternary |
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