山西大同与晋中盆地全新世活动断裂定量研究中热释光与~(14)C测年方法应用
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摘要
文章通过对山西断陷系内 4条边界活动断裂带开展全新世活动定量研究中实测的 6 7个热释光测年样品及 2 0个1 4C测年样品的实例分析 ,讨论了在断错地貌研究和探槽全新世古地震研究中 ,地层测年样品帮助确定断层活动事件年代、判断探槽内古地震事件的时间跨度、古地震事件的完整性及垂直断距的不确定性等方面发挥的作用 ;并讨论了少量热释光样品出现年代倒置现象的原因。
In order to dating Holocene paleoearthquakes, 67 samples for Thermoluminescence (TL) and 20 samples for 14 C were used. Samples were taken near the active faults including the Kouquan fault and the northern piedmont fault of Mt. Hengshan on the western and southern boundary of Datong basin, and the Taigu fault and the Jiaocheng fault on the eastern and western boundary of Jinzhong basin respectively. The important role of 14 C and TL dating in determining the age of dislocated geomorphology and paleo-earthquake was discusses. In the geomorphological investigation 28 TL samples and 3 14 C samples were dated. Among them, 8 TL-samples were taken from the back-border of alluvial fans; 7 TL samples from the bottom of gullies and the first and second order terraces; 13 TL-samples from the front and back border of loess platform. 3 14 C samples were taken from loam layers in the first order terrace on upthrown wall of the fault. Only three TL ages contradict with others, and therefore not used. The dating results indicate that the upper deposits at the alluvial fans back-borders on the downthrow side of the faults in Datong basin formed during Middle Holocene. While the strata at the foot of the upthrown side along the newest dislocated faces of the Taigu and Jiaocheng fault can be dated to Early Holocene. Therefore, the ages of deposits proved that the multiple activities on the Kouquan fault and on the northern piedmont fault of Mt. Hengshan took place along the main fault planes in between bedrock and back margin of alluvial fans. It also proved that the fault planes of Jiaocheng fault and partial segments of the Taigu fault are distributed as step faults. The newest activities of the faults migrate towards the basin. Ten big trenches have been opened along the four faults in the research. Our study on these trenches, showed that fourteen strong earthquakes took place along the four faults during Holocene, four on the Kouquan and Taigu fault and three on the northern piedmont fault of Mt. Hengshan and the Jiaocheng fault. Along the faults, 39 TL and 17 14 C samples were dated. Among them, 12 14 C and 15 TL datings were used for determining the upper or lower-limit of 13 paleo-earthquake events on the four faults. 5 14 C and 16 TL samples were used for determining the age of strata. 8 TL ages showed inversed chronology, three of them were taken from the open fissure wedge and collapse wedge near the fault planes in trenches. Samples taken from the top layer of the trenches may help to determine the age of morphological planes, and that from the bottom may help to determine the time span of paleo-earthquake events, their integrity, and the uncertainty of vertical offset of the fault. The loose deposits between the two sides of faults in the bottom of trenches along the Kouquan fault, the Taigu fault, and the Jiaocheng fault all exhibit a long time-span, indicating that these faults have had multiple activities during the time interval. The oldest deposit on the downthrow side of the three faults is not older than Middle Holocene. It indicates that the paleo-earthquake events during Early Holocene might be missing. Finally, the reasons for a few TL age reversal were also discussed. Besides the age of deposits in the tensile fissure wedges and in collapse wedges is older than the underneath layers; there are also TL ages older than those of 14 C from the same layers as well as the age of upper deposit in a trench older than the lower one. The latter is probably man-made. Another reason could be that sample site in geomorphologic investigation are not deep enough.
In order to dating Holocene paleoearthquakes, 67 samples for Thermoluminescence (TL) and 20 samples for 14 C were used. Samples were taken near the active faults including the Kouquan fault and the northern piedmont fault of Mt. Hengshan on the western and southern boundary of Datong basin, and the Taigu fault and the Jiaocheng fault on the eastern and western boundary of Jinzhong basin respectively. The important role of 14 C and TL dating in determining the age of dislocated geomorphology and paleo-earthquake was discusses. In the geomorphological investigation 28 TL samples and 3 14 C samples were dated. Among them, 8 TL-samples were taken from the back-border of alluvial fans; 7 TL samples from the bottom of gullies and the first and second order terraces; 13 TL-samples from the front and back border of loess platform. 3 14 C samples were taken from loam layers in the first order terrace on upthrown wall of the fault. Only three TL ages contradict with others, and therefore not used. The dating results indicate that the upper deposits at the alluvial fans back-borders on the downthrow side of the faults in Datong basin formed during Middle Holocene. While the strata at the foot of the upthrown side along the newest dislocated faces of the Taigu and Jiaocheng fault can be dated to Early Holocene. Therefore, the ages of deposits proved that the multiple activities on the Kouquan fault and on the northern piedmont fault of Mt. Hengshan took place along the main fault planes in between bedrock and back margin of alluvial fans. It also proved that the fault planes of Jiaocheng fault and partial segments of the Taigu fault are distributed as step faults. The newest activities of the faults migrate towards the basin. Ten big trenches have been opened along the four faults in the research. Our study on these trenches, showed that fourteen strong earthquakes took place along the four faults during Holocene, four on the Kouquan and Taigu fault and three on the northern piedmont fault of Mt. Hengshan and the Jiaocheng fault. Along the faults, 39 TL and 17 14 C samples were dated. Among them, 12 14 C and 15 TL datings were used for determining the upper or lower-limit of 13 paleo-earthquake events on the four faults. 5 14 C and 16 TL samples were used for determining the age of strata. 8 TL ages showed inversed chronology, three of them were taken from the open fissure wedge and collapse wedge near the fault planes in trenches. Samples taken from the top layer of the trenches may help to determine the age of morphological planes, and that from the bottom may help to determine the time span of paleo-earthquake events, their integrity, and the uncertainty of vertical offset of the fault. The loose deposits between the two sides of faults in the bottom of trenches along the Kouquan fault, the Taigu fault, and the Jiaocheng fault all exhibit a long time-span, indicating that these faults have had multiple activities during the time interval. The oldest deposit on the downthrow side of the three faults is not older than Middle Holocene. It indicates that the paleo-earthquake events during Early Holocene might be missing. Finally, the reasons for a few TL age reversal were also discussed. Besides the age of deposits in the tensile fissure wedges and in collapse wedges is older than the underneath layers; there are also TL ages older than those of 14 C from the same layers as well as the age of upper deposit in a trench older than the lower one. The latter is probably man-made. Another reason could be that sample site in geomorphologic investigation are not deep enough.
引文
1 邓起东.活动断裂研究的进展和方向.见:《活动断裂研究》编委会编.活动断裂研究(1).北京:地震出版社,1991.1～6
DengQidong.Progressanddirectionofactivefaultresearch.In:Boardof“ResearchonActiveFault”ed.ResearchonActiveFault1.Beijing:SeismologicalPress,1991.1～6
2 陈文寄,彭 贵主编.年轻地质体的年代测定.北京:地震出版社,1991.1～297
ChenWenji,PengGuieds.DatingofYoungGeologicalSystem.Beijing:SeismologicalPress,1991.1～297
3 计凤桔,郑公望,李建平.热释光技术应用的新进展.见:陈文寄,计凤桔,王 非主编.年轻地质体的年代测定(续).北京:地震出版社,1999.184～200
JiFengju,ZhengGongwang,LiJianping.Newprogressinapplicationofthermoluminescenetechnique.In:ChenWenji,JiFengju,WangFeieds.DatingofYoungGeologicalSystem(continuation).Beijing:SeismologicalPress,1999.184～200
4 卢演俦.活动构造测年方法和年代学研究的现状与问题.见:国家地震局地质研究所编.现今地球动力学研究及其应用.北京:地震出版社,1994.380～388
LuYanchou.Presentstateandproblemsondatingmethodsforactivetectonicandgeochronologicresearch.In:InstituteofGeology,StateSeismologicalBureaued.ResearchonModernGeodynamicsandItsApplication.Beijing:SeismologicalPress,1994.380～388
5 邓起东,冯先岳,杨晓平等.利用大型探槽研究新疆北天山玛纳斯和吐谷鲁逆断裂-褶皱带全新世古地震.见:《活动断裂研究》编委会,国家地震局地质研究所编.活动断裂研究(3).北京:地震出版社,1994.1～8
DengQidong,FengXianyu,YangXiaopingetal.StudyonHolocenepaleoearthquakesbylargetrenchintheManasTuguluReversefaultandfoldzonealongnorthernMarginofTianshan,inXinjiang.In:Boardof“ResearchonActiveFault”,InstituteofGeology,StateSeismologicalBureaueds.ResearchonActiveFault3.Beijing:SeismologicalPress,1994.1～8
6 吴卫民,李 克,马保起等.大青山山前断裂带大型组合探槽的全新世古地震研究.见:《活动断裂研究》编委会,国家地震局地质研究所.活动断裂研究(4).北京:地震出版社,1995.123～132
WuWeiming,LiKe,MaBaoqietal.ResearchonHolocenepaleoearthquakesusinglargecombinatedtrenchalongtheDaqingshanpiedmontfault,InnerMongolia.In:Boardof“ResearchonActiveFault”,InstituteofGeology,StateSeismologicalBureaueds.ResearchonActiveFault4.Beijing:SeismologicalPress,1995.123～132
7 冉勇康,段瑞涛,邓起东等.海原断裂高湾子地点三维探槽的开挖与古地震研究.地震地质,1997,19(2):97～107
RanYongkang,DuanRuitao,DengQidongetal.3DtrenchexcavationandpaleoseismologyatGaowanzioftheHaiyuanfault.SeismologyandGeology,1997,19(2):97～107
8 冉勇康,邓起东,杨晓平等.1679年三河-平谷8级地震发震断层的古地震及其重复间隔.地震地质,1997,19(3):193～201
RanYongkang,DengQidong,YangXiaopingetal.Paleoearthquakesandrecurrenceintervalontheseismogenicfaultof1679SanhePingguM8earthquake,HebeiandBeijing.SeismologyandGeology,1997,19(3):193～201
9 江娃利,侯治华,肖振敏等.北京平原夏垫断裂齐心庄探槽古地震事件分析.地震地质,2000,22(4):413～422
JiangWali,HouZhihua,XiaoZhenminetal.StadyonpaleoearthquakesofQixinzhuangtrenchattheXiadianfault,BeijingPlain.SeismologyandGeology,2000,22(4):413～422
10 江娃利,侯治华,谢新生.北京平原南口—孙河断裂带昌平旧县探槽古地震事件研究.中国科学(D辑),2001,31(6):501～509
JiangWali,HouZhihua,XieXinsheng.ResearchonpaleoearthquakesinJiuxiantrenchesacrossNankouSunhefaultzoneinChangpingCountyofBeijingPlain.ScienceinChina(SeriesD),2002,45(2):160～173
11 谢新生,江娃利,王 瑞等.山西大同盆地口泉断裂全新世古地震活动.地震地质,2003,25(3):359～374
XieXinsheng,JiangWali,WangRuietal.Holocenepaleo seismicactivitiesontheKouquanFaultZone,DatongBasin,ShanxiProvince.SeismologyandGeology,2003,25(3):359～374
12 江娃利,谢新生,王焕贞等.山西大同盆地恒山北缘断裂全新世古地震活动.中国地震,2003,19(1):8～19
JiangWali,XieXinsheng,WangHuanzhenetal.HolocenepalaeoseismicactivitiesalongthenorthernpiedmontFaultofHengshanMountain,DatongBasin,ShanxiProvince.EarthquakeResearchinChina,2003,9(1):8～19
13 谢新生,江娃利,王焕贞等.山西太谷断裂带全新世活动及其与1303年洪洞8级地震关系.地震学报,2004,26(3):281～293
XieXinsheng,JiangWali,WangHuanzhenetal.HoloceneactivitiesoftheTaiguFaultZone,ShanxiProvince,inrelationtothe1303HongdongEarthquakeM =8.ActaSeismologicaSinica,2004,17(3):307～320
14 江娃利,谢新生,王 瑞等.山西交城断裂全新世活动特征及古地震研究.地震研究,2004,27(2):184～189
JiangWali,XieXinsheng,WangRuietal.Preliminarystud
DengQidong.Progressanddirectionofactivefaultresearch.In:Boardof“ResearchonActiveFault”ed.ResearchonActiveFault1.Beijing:SeismologicalPress,1991.1～6
2 陈文寄,彭 贵主编.年轻地质体的年代测定.北京:地震出版社,1991.1～297
ChenWenji,PengGuieds.DatingofYoungGeologicalSystem.Beijing:SeismologicalPress,1991.1～297
3 计凤桔,郑公望,李建平.热释光技术应用的新进展.见:陈文寄,计凤桔,王 非主编.年轻地质体的年代测定(续).北京:地震出版社,1999.184～200
JiFengju,ZhengGongwang,LiJianping.Newprogressinapplicationofthermoluminescenetechnique.In:ChenWenji,JiFengju,WangFeieds.DatingofYoungGeologicalSystem(continuation).Beijing:SeismologicalPress,1999.184～200
4 卢演俦.活动构造测年方法和年代学研究的现状与问题.见:国家地震局地质研究所编.现今地球动力学研究及其应用.北京:地震出版社,1994.380～388
LuYanchou.Presentstateandproblemsondatingmethodsforactivetectonicandgeochronologicresearch.In:InstituteofGeology,StateSeismologicalBureaued.ResearchonModernGeodynamicsandItsApplication.Beijing:SeismologicalPress,1994.380～388
5 邓起东,冯先岳,杨晓平等.利用大型探槽研究新疆北天山玛纳斯和吐谷鲁逆断裂-褶皱带全新世古地震.见:《活动断裂研究》编委会,国家地震局地质研究所编.活动断裂研究(3).北京:地震出版社,1994.1～8
DengQidong,FengXianyu,YangXiaopingetal.StudyonHolocenepaleoearthquakesbylargetrenchintheManasTuguluReversefaultandfoldzonealongnorthernMarginofTianshan,inXinjiang.In:Boardof“ResearchonActiveFault”,InstituteofGeology,StateSeismologicalBureaueds.ResearchonActiveFault3.Beijing:SeismologicalPress,1994.1～8
6 吴卫民,李 克,马保起等.大青山山前断裂带大型组合探槽的全新世古地震研究.见:《活动断裂研究》编委会,国家地震局地质研究所.活动断裂研究(4).北京:地震出版社,1995.123～132
WuWeiming,LiKe,MaBaoqietal.ResearchonHolocenepaleoearthquakesusinglargecombinatedtrenchalongtheDaqingshanpiedmontfault,InnerMongolia.In:Boardof“ResearchonActiveFault”,InstituteofGeology,StateSeismologicalBureaueds.ResearchonActiveFault4.Beijing:SeismologicalPress,1995.123～132
7 冉勇康,段瑞涛,邓起东等.海原断裂高湾子地点三维探槽的开挖与古地震研究.地震地质,1997,19(2):97～107
RanYongkang,DuanRuitao,DengQidongetal.3DtrenchexcavationandpaleoseismologyatGaowanzioftheHaiyuanfault.SeismologyandGeology,1997,19(2):97～107
8 冉勇康,邓起东,杨晓平等.1679年三河-平谷8级地震发震断层的古地震及其重复间隔.地震地质,1997,19(3):193～201
RanYongkang,DengQidong,YangXiaopingetal.Paleoearthquakesandrecurrenceintervalontheseismogenicfaultof1679SanhePingguM8earthquake,HebeiandBeijing.SeismologyandGeology,1997,19(3):193～201
9 江娃利,侯治华,肖振敏等.北京平原夏垫断裂齐心庄探槽古地震事件分析.地震地质,2000,22(4):413～422
JiangWali,HouZhihua,XiaoZhenminetal.StadyonpaleoearthquakesofQixinzhuangtrenchattheXiadianfault,BeijingPlain.SeismologyandGeology,2000,22(4):413～422
10 江娃利,侯治华,谢新生.北京平原南口—孙河断裂带昌平旧县探槽古地震事件研究.中国科学(D辑),2001,31(6):501～509
JiangWali,HouZhihua,XieXinsheng.ResearchonpaleoearthquakesinJiuxiantrenchesacrossNankouSunhefaultzoneinChangpingCountyofBeijingPlain.ScienceinChina(SeriesD),2002,45(2):160～173
11 谢新生,江娃利,王 瑞等.山西大同盆地口泉断裂全新世古地震活动.地震地质,2003,25(3):359～374
XieXinsheng,JiangWali,WangRuietal.Holocenepaleo seismicactivitiesontheKouquanFaultZone,DatongBasin,ShanxiProvince.SeismologyandGeology,2003,25(3):359～374
12 江娃利,谢新生,王焕贞等.山西大同盆地恒山北缘断裂全新世古地震活动.中国地震,2003,19(1):8～19
JiangWali,XieXinsheng,WangHuanzhenetal.HolocenepalaeoseismicactivitiesalongthenorthernpiedmontFaultofHengshanMountain,DatongBasin,ShanxiProvince.EarthquakeResearchinChina,2003,9(1):8～19
13 谢新生,江娃利,王焕贞等.山西太谷断裂带全新世活动及其与1303年洪洞8级地震关系.地震学报,2004,26(3):281～293
XieXinsheng,JiangWali,WangHuanzhenetal.HoloceneactivitiesoftheTaiguFaultZone,ShanxiProvince,inrelationtothe1303HongdongEarthquakeM =8.ActaSeismologicaSinica,2004,17(3):307～320
14 江娃利,谢新生,王 瑞等.山西交城断裂全新世活动特征及古地震研究.地震研究,2004,27(2):184～189
JiangWali,XieXinsheng,WangRuietal.Preliminarystud
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