山西交城断裂带西张探槽全新世古地震研究
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摘要
西张探槽①位于山西太原市西北10km,沿交城断裂带北段NNW方向高4.6m的低陡坎前缘开挖。探槽长108m,宽8m,深10m,揭露18层地层。探槽上部地层为亚砂土,探槽内断层下降盘的上部地层为一套砾石层,下部地层为一套褐色垆土与亚砂土互层,断层的上升盘地层以亚砂土为主夹砾石层。探槽揭露出3条断面,断面的上断点距地表1.5m,断错的最新地层距今(3.74±0.06)ka。探槽揭示出断面、地层断错、崩积楔、地层倾斜等现象。由探槽揭露出的地层与断层的关系可知早全新世以来交城断裂带曾发生3次断层活动事件,其时间分别为距今(3.74±0.06)～(3.06±0.26)ka、(8.35±0.09)～(3.74±0.06)ka与(10.66±0.85)～(8.35±0.09)ka,具有2.6～3.6ka的强震重复间隔;3次同事件最小垂直位移分别为3.0m、2.5m及3.2m。西张探槽的意义在于揭示了历史上未有强震记载的晋中盆地几千年前有过多次强震活动。西张探槽获得的交城断裂带全新世古地震活动的依据,对评价太原市未来的强震危险性具有重要意义。
Xizhang trench is located at 10 kilometers northwest of the Taiyuan City,Shanxi Province,and it was excavated at the front of a NNW-trending scarp of 4.6m height on the northern segment of the Jiaocheng Fault zone.The dimensions of the trench are 108m in length,8m in width,and 10m in depth.There are 18 strata revealed in the trench.The upper stratum is sandy loam;the upper stratum of the downthrown block of the fault is gravel,the lower stratum is interbed of brown loam and sandy loam.The strata on the upthrown block of the fault are sandy loam containing gravel.The trench shows 3 fault planes,and the upper fault point on the fault plane is 1.5m deep from the ground surface,the newest dislocated stratum is(3.74±0.06)ka BP.The trench reveals a lot of deformation traces,such as fault plane,dislocated strata,colluvial wedge and the dipping of formation.The relation between the strata and the faults in the trench shows that 3 paleoearthquake events have occurred at the Jiaocheng Fault zone since Early Holocene,they are about(3.74±0.06)～(3.06±0.26)ka BP,(8.35±0.09)～(3.74±0.06)ka BP,and(10.66±0.85)～(8.35±0.09)ka BP,respectively.The average interval of the events is2.6～3.6ka.The minimum coseismic vertical displacements of the 3 events are 3.0m,2.5m,and 3.2m,respectively.The significance of Xizhang trench is that the Jiaocheng Fault used to be active thousands years ago,though there wasn't M≥7 earthquake recorded in historical words.The evidence of newest activities of the Jiaocheng Fault zone during Holocene is important for earthquake safety assessment of Taiyuan City in the future.
Xizhang trench is located at 10 kilometers northwest of the Taiyuan City,Shanxi Province,and it was excavated at the front of a NNW-trending scarp of 4.6m height on the northern segment of the Jiaocheng Fault zone.The dimensions of the trench are 108m in length,8m in width,and 10m in depth.There are 18 strata revealed in the trench.The upper stratum is sandy loam;the upper stratum of the downthrown block of the fault is gravel,the lower stratum is interbed of brown loam and sandy loam.The strata on the upthrown block of the fault are sandy loam containing gravel.The trench shows 3 fault planes,and the upper fault point on the fault plane is 1.5m deep from the ground surface,the newest dislocated stratum is(3.74±0.06)ka BP.The trench reveals a lot of deformation traces,such as fault plane,dislocated strata,colluvial wedge and the dipping of formation.The relation between the strata and the faults in the trench shows that 3 paleoearthquake events have occurred at the Jiaocheng Fault zone since Early Holocene,they are about(3.74±0.06)～(3.06±0.26)ka BP,(8.35±0.09)～(3.74±0.06)ka BP,and(10.66±0.85)～(8.35±0.09)ka BP,respectively.The average interval of the events is2.6～3.6ka.The minimum coseismic vertical displacements of the 3 events are 3.0m,2.5m,and 3.2m,respectively.The significance of Xizhang trench is that the Jiaocheng Fault used to be active thousands years ago,though there wasn't M≥7 earthquake recorded in historical words.The evidence of newest activities of the Jiaocheng Fault zone during Holocene is important for earthquake safety assessment of Taiyuan City in the future.
引文
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林传勇,陈孝德,史兰斌.2007.山西太原交城断裂西张探槽的显微构造和显微沉积学分析[J].地震地质,29(2):294—310.LIN Chuan-yong,CHEN Xiao-de,SHI Lan-bin.2007.Microstructural and micro-sedimentologic analyses of the trench across the Jiaocheng Fault,Xizhangcun village,Taiyuan,Shanxi Province[J].Seismology and Geology,29(2):294—310(in Chinese).
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马保起,许桂林,盛小青,等.1999.山西交城断裂活动的构造地貌学研究[A].见:中国地震局地壳应力研究所编.地壳构造与地壳应力文集(12).北京:地震出版社.7—15.MA Bao-qi,XU Gui-lin,SHENG Xiao-qing,et al.1999.A study on tectonomorphology along the Jiaocheng fault,Shanxi Province[A].In:Institute of Crustal Dynamics,CEA(ed).Crustal Tectonics and Crustal Stress(12).Seismological Press,Beijing.7—15(in Chinese).
苏宗正.1988.山西断陷带地震活动的新构造背景[J].山西地震,(4):2—6.SU Zong-zheng.1988.Neotectonic background of seismic activities in the Shanxi fault-depression zone[J].Earth-quake Research in Shanxi,(4):2—6(in Chinese).
肖振敏,江娃利.1998.山西断陷带历史强震及全新世古地震地表破裂特征[A].见:中国地震局地壳应力研究所编.地壳构造与地壳应力文集(11).北京:地震出版社.1—12.XIAO Zhen-min,JIANG Wa-li.1998.Characteristics of surface rupture belts formed by historical and paleoearthquakesalong the Shanxi fault depression zone[A].In:Institute of Crustal Dynamics,CEA(ed).Crustal Tectonics andCrustal Stress(11).Seismological Press,Beijing.1—12(in Chinese).
许桂林,马保起,江娃利.1998.山西交城断裂带第四纪活动习性及其分段特征[A].见:中国地震局地壳应力研究所编.地壳构造与地壳应力文集(11).北京:地震出版社.13—21.XU Gui-lin,MA Bao-qi,JIANG Wa-li.1998.The behavior and segmentation of the Jiaocheng,Shanxi active fault[A].In:Institute of Crustal Dynamics,CEA(ed).Crustal Tectonics and Crustal Stress(11).SeismologicalPress,Beijing.13—21(in Chinese).
邓起东,王克鲁,汪一鹏,等.1973.山西隆起区断陷地震带地震地质条件及地震发展趋势概述[J].地质科学,(1):37—47.DENG Qi-dong,WANG Ke-lu,WANG Yi-peng,et al.1973.A reviewof seismo-geological conditions and seismic ac-tivity tendency in Shanxi faulted depression of Shanxi uplift zone[J].Scientia Geologica Sinica,(1):37—47(inChinese).
邓起东.1982.中国的活动断裂[A].见:中国地震学会地震地质专业委员会编.中国活动断裂.北京:地震出版社.19—27.DENG Qi-dong.1982.The active fault in China[A].In:Committee on Seismogeology of the Seismological Society ofChina(ed).The Active Faults in China.Seismological Press,Beijing.19—27(in Chinese).
邓起东,于贵华,叶文华.1993.地震地表破裂参数与震级的关系[A].见:国家地震局地质研究所编.活动断裂研究(2).北京:地震出版社.247—264.DENG Qi-dong,YU Gui-hua,YE Wen-hua.1993.Relationships between earthquake magnitude and parameters of sur-face ruptures associated with historical earthquakes[A].In:Institute of Geology,SSB(ed).Research on ActiveFault(2).Seismological Press,Beijing.247—264(in Chinese).
丁国瑜.1982.中国内陆活动断裂基本特征的讨论[A].见:中国地震学会地震地质专业委员会编.中国活动断裂.北京:地震出版社.1—9.DING Guo-yu.1982.A discussion on the basic characteristics of the active faults in the Chinese continent[A].In:Committee on Seismogeology of the Seismological Society of China(ed).The Active Faults in China.Seismologi-cal Press,Beijing.1—9(in Chinese).
江娃利,聂宗笙,张康富.1993.山西交城断裂全新世活动证据及第四纪活动历史[A].见:国家地震局地壳应力研究所编.地壳构造与地壳应力文集(6).北京:地震出版社.98—104.JIANG Wa-li,NIE Zong-sheng,ZHANG Kang-fu.1993.The Holocene active evidence and the Quaternary active histo-ry about the Jiaocheng fault in Shanxi[A].In:Institute of Crustal Dynamics,SSB(ed).Crustal Tectonics andCrustal Stress(6).Seismological Press,Beijing.98—104(in Chinese).
江娃利,谢新生,王瑞,等.2004.山西断陷系交城断裂全新世古地震活动初步研究[J].地震研究,27(2):184—190.JIANG Wa-li,XIE Xin-sheng,WANG Rui,et al.2004.Preliminary study on activity of Holocene paleoearthquakes a-long the Jiaochen fault in the Shanxi down-faulted system[J].Journal of Seismological Research,27(2):184—190(in Chinese).
林传勇,陈孝德,史兰斌.2007.山西太原交城断裂西张探槽的显微构造和显微沉积学分析[J].地震地质,29(2):294—310.LIN Chuan-yong,CHEN Xiao-de,SHI Lan-bin.2007.Microstructural and micro-sedimentologic analyses of the trench across the Jiaocheng Fault,Xizhangcun village,Taiyuan,Shanxi Province[J].Seismology and Geology,29(2):294—310(in Chinese).
刘光勋,肖振敏.1982.山西地堑系及其地震构造特征[A].见:中国地质学会构造地质专业委员会编.第二届全国地质构造学术会议论文选集(第三卷):中新生代构造.北京:科学出版社.66—74.LIU Guang-xun,XIAO Zhen-min.1982.Shanxi graben system and its seismotectonics[A].In:Commission on Tec-tonics of the Geological Society of China(ed).Selected Papers from the Second Congress on Tectonics.VolumeⅢ.Science Press,Beijing.66—74(in Chinese).
马保起,许桂林,盛小青,等.1999.山西交城断裂活动的构造地貌学研究[A].见:中国地震局地壳应力研究所编.地壳构造与地壳应力文集(12).北京:地震出版社.7—15.MA Bao-qi,XU Gui-lin,SHENG Xiao-qing,et al.1999.A study on tectonomorphology along the Jiaocheng fault,Shanxi Province[A].In:Institute of Crustal Dynamics,CEA(ed).Crustal Tectonics and Crustal Stress(12).Seismological Press,Beijing.7—15(in Chinese).
苏宗正.1988.山西断陷带地震活动的新构造背景[J].山西地震,(4):2—6.SU Zong-zheng.1988.Neotectonic background of seismic activities in the Shanxi fault-depression zone[J].Earth-quake Research in Shanxi,(4):2—6(in Chinese).
肖振敏,江娃利.1998.山西断陷带历史强震及全新世古地震地表破裂特征[A].见:中国地震局地壳应力研究所编.地壳构造与地壳应力文集(11).北京:地震出版社.1—12.XIAO Zhen-min,JIANG Wa-li.1998.Characteristics of surface rupture belts formed by historical and paleoearthquakesalong the Shanxi fault depression zone[A].In:Institute of Crustal Dynamics,CEA(ed).Crustal Tectonics andCrustal Stress(11).Seismological Press,Beijing.1—12(in Chinese).
许桂林,马保起,江娃利.1998.山西交城断裂带第四纪活动习性及其分段特征[A].见:中国地震局地壳应力研究所编.地壳构造与地壳应力文集(11).北京:地震出版社.13—21.XU Gui-lin,MA Bao-qi,JIANG Wa-li.1998.The behavior and segmentation of the Jiaocheng,Shanxi active fault[A].In:Institute of Crustal Dynamics,CEA(ed).Crustal Tectonics and Crustal Stress(11).SeismologicalPress,Beijing.13—21(in Chinese).
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