东昆仑断裂带东段塔藏断裂晚第四纪古地震研究
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摘要
塔藏断裂位于东昆仑断裂带东段,属于"玛曲空区"范围,汶川M_S8.0级地震对该区域造成了应力的加载,但是本区尚未开展古地震方面研究,地震危险性认识不足。通过断错地貌实测、古地震探槽、~(14)C定年等方法,在坡中谷、断塞塘附近位置开挖两处探槽,获得了一些古地震方面的认识。探槽附近微地貌测量结果表明,断错量主要分布在两个范围区间72m和71m,以及27m,25和22m,两区间之间近倍数关系,推测由多次地震事件造成。两处探槽采集~(14)C样品共计19个,探槽剖面分别记录了2次古地震事件,事件发生的层位与年龄具有一定的可比性,经逐次限定后得到2次古地震事件,时间分别为320±30～500±30aB.P.和2730±30～2840±30aB.P.;最近一次古地震离逝时间为320±30～500±30aB.P.;实际重复间隔约为2300a,与东昆仑断裂玛曲段的重复间隔较为接近。
The East Kunlun active fault zone in northern Tibetan is typically characterized by sinistral strike-lip fault. Tazang Fault is situated in the east segment of the East Kunlun active fault as well as in the scope of " Maqu seismic gap".The coulomb stress on the region around Tazang fault was increased due to the Wenchuan M_s8.0 earthquake. However,there is little quake-proof research work about paleoearthquakes and the seismic risk of the region has not been profoundly recognized.Based on field investigations,the interpretation of remote sensing images,the measurement of earthquake-related landforms by difference global positioning system,trench excavating and radiocarbon dating of C by Accelerator Mass Spectrometry(AMS),the paper tries to find out some evidences and knowledge about the characteristics of paleoearthquakes of the fault in the Late Quaternary.Two trenches were excavated near the sag- ponds,the lower edge of reverse scar and slop-hanging-ditch structure,which is perpendicular to the fault-strike.High- precision surveying work was carried out by the method of difference global positioning system around the two trenches in order to carefully study the characteristic of geomorphology near the trenches and define the positions of trenches. According to the statistics of 1364 difference global positioning system measurement data around Trench 1 (33°45'45.50"N,103°15'25.70"E),the left-slip displacements of three nearly north-south trending gullies perpendicular to the fault-strike are respectively as follows:72m,27m,and 25m.On the other hand,based on the 3566 difference global positioning system measurement data around Trench 2(33°47'37.00"N,103°10'8.50"E),which is 10km to the west of Trench 1,the left-slip displacement of a nearly north-south trending terrace ridge on the west side of the trench nearly perpendicular to the fault-strike is about 71m and the left-slip displacement of a nearly northsouth trending terrace ridge on the east side of the trench is about 22m. All above displacements are mainly distributed in the two ranges;72～71m and 27～22m,which are close to multiple relation,probably caused by paleoearthquakes.7 dating samples of C from the west geological log of Trench 1 and 12 dating samples of C from the east geological log of Trench 2 were taken,and 19 final infallible results of radiocarbon dating came out,which were tested by the Beta Analytic Limited utilized Accelerator Mass Spectrometry and chronological calibration.2 paleo-earthquake events since the Late Quaternary are uncovered by the two trenches.Based on the comparison diagram of the two trenches' stratigraphic columns,dating results of C and multiple trench constraining method,a conclusion can be made that the occurrence time of the 2 constrained events are respectively as follows;320±30～500±30aB.P.,2730±30～2840±30 aB.P.,and the departure time of the most recent earthquake is 320±30～500±30aB.P.,and the recurrence interval of earthquake near the fault is about 2300a. Given above discussion,it shows consistency between the Tazang fault and Maqu fault in the recurrence interval. Further,Tazang Fault remains not only encircled in a growth stage of coulomb stress but also situated in the seismic gap,and has certain seismic risk.The future seismic risk of this region deserves more attention. This paper firstly concludes that 2 paleoearthquake events occurred along the Tazang Fault,and enriches the information of seismicity of the East Kunlun active fault zone.It will perform a role in seismic hazard assessment in this region.
The East Kunlun active fault zone in northern Tibetan is typically characterized by sinistral strike-lip fault. Tazang Fault is situated in the east segment of the East Kunlun active fault as well as in the scope of " Maqu seismic gap".The coulomb stress on the region around Tazang fault was increased due to the Wenchuan M_s8.0 earthquake. However,there is little quake-proof research work about paleoearthquakes and the seismic risk of the region has not been profoundly recognized.Based on field investigations,the interpretation of remote sensing images,the measurement of earthquake-related landforms by difference global positioning system,trench excavating and radiocarbon dating of C by Accelerator Mass Spectrometry(AMS),the paper tries to find out some evidences and knowledge about the characteristics of paleoearthquakes of the fault in the Late Quaternary.Two trenches were excavated near the sag- ponds,the lower edge of reverse scar and slop-hanging-ditch structure,which is perpendicular to the fault-strike.High- precision surveying work was carried out by the method of difference global positioning system around the two trenches in order to carefully study the characteristic of geomorphology near the trenches and define the positions of trenches. According to the statistics of 1364 difference global positioning system measurement data around Trench 1 (33°45'45.50"N,103°15'25.70"E),the left-slip displacements of three nearly north-south trending gullies perpendicular to the fault-strike are respectively as follows:72m,27m,and 25m.On the other hand,based on the 3566 difference global positioning system measurement data around Trench 2(33°47'37.00"N,103°10'8.50"E),which is 10km to the west of Trench 1,the left-slip displacement of a nearly north-south trending terrace ridge on the west side of the trench nearly perpendicular to the fault-strike is about 71m and the left-slip displacement of a nearly northsouth trending terrace ridge on the east side of the trench is about 22m. All above displacements are mainly distributed in the two ranges;72～71m and 27～22m,which are close to multiple relation,probably caused by paleoearthquakes.7 dating samples of C from the west geological log of Trench 1 and 12 dating samples of C from the east geological log of Trench 2 were taken,and 19 final infallible results of radiocarbon dating came out,which were tested by the Beta Analytic Limited utilized Accelerator Mass Spectrometry and chronological calibration.2 paleo-earthquake events since the Late Quaternary are uncovered by the two trenches.Based on the comparison diagram of the two trenches' stratigraphic columns,dating results of C and multiple trench constraining method,a conclusion can be made that the occurrence time of the 2 constrained events are respectively as follows;320±30～500±30aB.P.,2730±30～2840±30 aB.P.,and the departure time of the most recent earthquake is 320±30～500±30aB.P.,and the recurrence interval of earthquake near the fault is about 2300a. Given above discussion,it shows consistency between the Tazang fault and Maqu fault in the recurrence interval. Further,Tazang Fault remains not only encircled in a growth stage of coulomb stress but also situated in the seismic gap,and has certain seismic risk.The future seismic risk of this region deserves more attention. This paper firstly concludes that 2 paleoearthquake events occurred along the Tazang Fault,and enriches the information of seismicity of the East Kunlun active fault zone.It will perform a role in seismic hazard assessment in this region.
引文
1闻学泽,杜方,张培震等.巴颜喀拉块体北和东边界大地震序列的关联性与2008年汶川地震.地球物理学报,2011,54(3): 706 -716,doi:10.3969/j.issn.0001 -5733.2011.03.010 Wen Xueze,Du Fang,Zhang Peizhen et al.Correlation of major earthquake sequences on the northern and eastern boundaries of the Bayan Har block,and its relation to the 2008 Wenchuan earthquake. Chinese Journal of Geophysics,2011,54(3 ):706 -716,doi: 10.3969/j.issn.0001 - 5733.2011.03.010
2张军龙,任金卫,付俊东等.东昆仑断裂带东部塔藏断裂地震地表破裂特征及其构造意义.地震,2012,32(1):1-16 Zhang Junlong,Ren Jinwei,Fu Jundong et al.Earthquake rupture features and tectonics significance of the Tazang Fault in the eastern part of the East Kunlun Fault Zones.Earthquake,2012,32(1):1 -16
3 Xu Xiwei,Yu Guihua,Klinger Y et al.Reevaluation of surface rupture parameters and faulting segmentation of the 2001 Kunlunshan earthquake(Afw7.8),northern Tibetan Plateau,China. Journal of Geophysical Research,2006,111(B5 ):673 - 684
4李陈侠.东昆仑断裂带东段(玛沁-玛曲)晚第四纪长期滑动习性研究.北京:中国地震局地质研究所博士论文,2009.1-154 Li Chenxia.The Long-term Faulting Behavior of the East Segment (Maqin to Maqu ) of the East Kunlun Fault since the Late Quaternary.Beijing:The Ph.D Dissertation of Institute of Geology, China Earthquake Administration,2009.1 - 154
5胡朝忠.塔藏断裂晚第四纪活动性研究.北京:中国地震局地震预测研究所硕士论文,2011.1-71 Hu Chaozhong.Late Quaternary Activity of the Tazang Fault. Beijing:The Master Dissertation of Institute of Earthquake Scicence,China Earthquake Administration,2011.1 -71
6 Kirby Eric,Harkins Nathan,Wang Erqi et al.Slip rate gradients along the eastern Kunlun fault.Tectonics,2007,26,TC2010,16.doi: 10.1029/2006TC002033
7任金卫,王敏.GPS观测的2001年昆仑山口西M_S8.1级地震地壳变形.第四纪研究,2005,25(1):34-44 Ren Jinwei,Wang Min.GPS Measured crustal deformation of the M_S8.1 Kunlun earthquake on November 14th 2001 in QinghaiXizang Plateau,China.Quaternary Sciences,2005,25(1 ):34 - 44
8邵志刚,周龙泉,蒋长胜等.2008年汶川M_S8.0地震对周边断层地震活动的影响.地球物理学报,2010,53(8):1784-1795, doi:10.3969/j.issn.0001 - 5733.2010.08.004 Shao Zhigang,Zhou Longquan,Jiang Changsheng et al.The impact of Wenchuan M_S8.0 earthquake on the seismic activity of surrounding faults.Chinese Journal of Geophysics,2010,53(8 ):1784 - 1795, doi:10.3969/j.issn.0001 -5733.2010.08.004
9张军龙,田勤俭,李智敏等.差分GPS方法在城市活断层探测中的应用探讨.地震,2007,27(3):74-82 Zhang Junlong,Tian Qinjian,Li Zhimin et al.Use of differential GPS in detecting active faults in cities.Earthquake,2007,27(3 ):74 - 82
10冉勇康.我国几个典型地点的古地震细研究和大地震重复行为探讨.北京:中国地震局地质研究所博士论文,1997.8-12 Ran Yongkang.Detailed Research of Paleoearthquakes at Several Typical Regions in China and Exploration of Recurrence Behavior of Large Earthquakes.Beijing:The Ph.D Dissertation of Institute of Geology,China Earthquake Administration,1997.8-12
11 McCalpin J.Trench Technology,for the Paleoseismology.In: Workshop of 30th International Geological Congress.Beijing, 1996.86-111
12田勤俭,任志坤,张军龙.则木河断裂带大箐梁子附近古地震组合探槽研究.地震地质,2008,30(2):400-411 Tian Qinjian,Ren Zhikun,Zhang Junlong.Study of paleoearthquakes by combined trench on Zemuhe Fault around Daqingliangzi, Xichang,Sichuan.Seismology and Geology,2008,30(2):400 -411
13 Sieh K E.A review of geological evidence for recurrence times of large earthquakes,in earthquake prediction——An international review.In:Simpson D W,Richards P G eds.American Geophysical Union,Wshington,D.C.1981,4:181 - 194
14 Wen Xueze.Assessment of time-dependent seismic hazards on segments of active fault,and its problem.Chinese Science Bulletin, 1998,43(14):1457-1466
15邓起东,汪一鹏,廖玉华等.断层崖崩积楔及贺兰山山前断裂全新世活动历史.科学通报,1984,29(9):557-560 Deng Qidong,Wang Yipeng,Liao Yuhua et al.Colluvialwedge of fault scarp and Holocene active history along the Helanshan Mt. ??piedmont fault.Chinese Science Bulletin,1984,29(9):557 -560
16陈立春,冉永康,陈杰等.龙门山前山断裂大地震原地重复发生的地质地貌证据.第四纪研究,2009,29(3):472-483 Chen Lichun,Ran Yongkang,Chen Jie et al.Geological and geomorphic evidence for repeatedly occurring severe earthquakes on fronter-range fault of Longmenshan,China.Quaternary Sciences, 2009,29(3):472 -483
17田勤俭,郝凯,王林等.汶川8.0级地质发震断层逆冲活动的地震地貌与古地震初步研究.第四纪研究,2009,29(3): 464-471 Tian Qinjian,Hao Kai,Wang Lin et al.Preliminary study of paleoearthquakes based on earthquake terrace and offset terrace investigation after Wenchuan M_S8.0 earthquake.Quaternary Sciences,2009,29(3):464 -471
18胡道功,叶培盛,吴珍汉等.东昆仑断裂带西大滩段全新世古地震研究.第四纪研究,2006,26(6):1012-1020 Hu Daogong,Ye Peisheng,Wu Zhenhan et al.Research on Holocene paleoearthquakes on the Xidatan segment of the East Kunlun Fault zone in northern Tibet.Quaternary Sciences,2006,26(6):1012 -1020
19刘静,徐锡伟,李岩峰等.以海原断裂甘肃老虎山段为例浅析走滑断裂古地震记录的完整性——兼论古地震研究的若干问题.地质通报,2007,26(6):650-660 Liu jing,Xu Xiwei,Li Yanfeng et al.On the completeness of paleoseismic records of strike-slip faults:An example from the Laohushan segment of the Haiyuan fault in Gansu,China——With a discussion of several problems in the paleoearthquake study. Geological Bulletin of China,2007,26(6):650 -660
20 Druffel E R M.Pluses of rapid ventilation in the North Atlantic surface ocean during the past century.Science,1997,275:1454 -1457
21甘肃省地质局.中华人民共和国区域地质矿产报告(1:20万)——巴西幅.兰州:1973.43-45 Gansu Geological Survey.Regional Geology and Mineral Resources Report of the People's Republic of China(1:200000 )——The Sheet of Baxi.Lanzhou:1973.43 - 45
22冉永康,邓起东.大地震重复特征与平均重复间隔的取值问题.地震地质,1999,24(4):316-323 Ran Yongkang,Deng Qidong.Recurrence behavior of large earthquakes and how to take advance recurrence interval of large earthquakes.Seismology and Geology,1999,24(4):316 -323
23杜平山.则木河活动断裂带大震复发问隔.四川地震,2000, (1-2):102-118 Du Pingshan.Recurrence interval on macroearthquake along the active fault of Zemuhe.Earthquake Research in Sichuan,2000,(1 - 2):102 -118
24毛凤英,张培震.古地震研究的逐次限定法与新疆北部主要断裂带的古地震研究.A-活动断裂研究(4).北京:地震出版社, 1995.153-164 Mao Fengying,Zhang Peizhen.Method for progressive constraint for paleoseismic events and paleoseismological study of major fault zone in northern Xinjiang.A-Research on Active Faults(4 ).Beijing: Seismological Press,1995.153 - 164
25何文贵,熊振,袁道阳等.东昆仑断裂带东段玛曲断裂古地震初步研究.中国地震,2006,22(2):126-134 He Wengui,Xiong Zhen,Yuan Daoyang et al.Palaeo-earthquake study on the Maqu Fault of East Kunlun active fault.Earthquake Research in China,2006,22(2):126 - 134
2张军龙,任金卫,付俊东等.东昆仑断裂带东部塔藏断裂地震地表破裂特征及其构造意义.地震,2012,32(1):1-16 Zhang Junlong,Ren Jinwei,Fu Jundong et al.Earthquake rupture features and tectonics significance of the Tazang Fault in the eastern part of the East Kunlun Fault Zones.Earthquake,2012,32(1):1 -16
3 Xu Xiwei,Yu Guihua,Klinger Y et al.Reevaluation of surface rupture parameters and faulting segmentation of the 2001 Kunlunshan earthquake(Afw7.8),northern Tibetan Plateau,China. Journal of Geophysical Research,2006,111(B5 ):673 - 684
4李陈侠.东昆仑断裂带东段(玛沁-玛曲)晚第四纪长期滑动习性研究.北京:中国地震局地质研究所博士论文,2009.1-154 Li Chenxia.The Long-term Faulting Behavior of the East Segment (Maqin to Maqu ) of the East Kunlun Fault since the Late Quaternary.Beijing:The Ph.D Dissertation of Institute of Geology, China Earthquake Administration,2009.1 - 154
5胡朝忠.塔藏断裂晚第四纪活动性研究.北京:中国地震局地震预测研究所硕士论文,2011.1-71 Hu Chaozhong.Late Quaternary Activity of the Tazang Fault. Beijing:The Master Dissertation of Institute of Earthquake Scicence,China Earthquake Administration,2011.1 -71
6 Kirby Eric,Harkins Nathan,Wang Erqi et al.Slip rate gradients along the eastern Kunlun fault.Tectonics,2007,26,TC2010,16.doi: 10.1029/2006TC002033
7任金卫,王敏.GPS观测的2001年昆仑山口西M_S8.1级地震地壳变形.第四纪研究,2005,25(1):34-44 Ren Jinwei,Wang Min.GPS Measured crustal deformation of the M_S8.1 Kunlun earthquake on November 14th 2001 in QinghaiXizang Plateau,China.Quaternary Sciences,2005,25(1 ):34 - 44
8邵志刚,周龙泉,蒋长胜等.2008年汶川M_S8.0地震对周边断层地震活动的影响.地球物理学报,2010,53(8):1784-1795, doi:10.3969/j.issn.0001 - 5733.2010.08.004 Shao Zhigang,Zhou Longquan,Jiang Changsheng et al.The impact of Wenchuan M_S8.0 earthquake on the seismic activity of surrounding faults.Chinese Journal of Geophysics,2010,53(8 ):1784 - 1795, doi:10.3969/j.issn.0001 -5733.2010.08.004
9张军龙,田勤俭,李智敏等.差分GPS方法在城市活断层探测中的应用探讨.地震,2007,27(3):74-82 Zhang Junlong,Tian Qinjian,Li Zhimin et al.Use of differential GPS in detecting active faults in cities.Earthquake,2007,27(3 ):74 - 82
10冉勇康.我国几个典型地点的古地震细研究和大地震重复行为探讨.北京:中国地震局地质研究所博士论文,1997.8-12 Ran Yongkang.Detailed Research of Paleoearthquakes at Several Typical Regions in China and Exploration of Recurrence Behavior of Large Earthquakes.Beijing:The Ph.D Dissertation of Institute of Geology,China Earthquake Administration,1997.8-12
11 McCalpin J.Trench Technology,for the Paleoseismology.In: Workshop of 30th International Geological Congress.Beijing, 1996.86-111
12田勤俭,任志坤,张军龙.则木河断裂带大箐梁子附近古地震组合探槽研究.地震地质,2008,30(2):400-411 Tian Qinjian,Ren Zhikun,Zhang Junlong.Study of paleoearthquakes by combined trench on Zemuhe Fault around Daqingliangzi, Xichang,Sichuan.Seismology and Geology,2008,30(2):400 -411
13 Sieh K E.A review of geological evidence for recurrence times of large earthquakes,in earthquake prediction——An international review.In:Simpson D W,Richards P G eds.American Geophysical Union,Wshington,D.C.1981,4:181 - 194
14 Wen Xueze.Assessment of time-dependent seismic hazards on segments of active fault,and its problem.Chinese Science Bulletin, 1998,43(14):1457-1466
15邓起东,汪一鹏,廖玉华等.断层崖崩积楔及贺兰山山前断裂全新世活动历史.科学通报,1984,29(9):557-560 Deng Qidong,Wang Yipeng,Liao Yuhua et al.Colluvialwedge of fault scarp and Holocene active history along the Helanshan Mt. ??piedmont fault.Chinese Science Bulletin,1984,29(9):557 -560
16陈立春,冉永康,陈杰等.龙门山前山断裂大地震原地重复发生的地质地貌证据.第四纪研究,2009,29(3):472-483 Chen Lichun,Ran Yongkang,Chen Jie et al.Geological and geomorphic evidence for repeatedly occurring severe earthquakes on fronter-range fault of Longmenshan,China.Quaternary Sciences, 2009,29(3):472 -483
17田勤俭,郝凯,王林等.汶川8.0级地质发震断层逆冲活动的地震地貌与古地震初步研究.第四纪研究,2009,29(3): 464-471 Tian Qinjian,Hao Kai,Wang Lin et al.Preliminary study of paleoearthquakes based on earthquake terrace and offset terrace investigation after Wenchuan M_S8.0 earthquake.Quaternary Sciences,2009,29(3):464 -471
18胡道功,叶培盛,吴珍汉等.东昆仑断裂带西大滩段全新世古地震研究.第四纪研究,2006,26(6):1012-1020 Hu Daogong,Ye Peisheng,Wu Zhenhan et al.Research on Holocene paleoearthquakes on the Xidatan segment of the East Kunlun Fault zone in northern Tibet.Quaternary Sciences,2006,26(6):1012 -1020
19刘静,徐锡伟,李岩峰等.以海原断裂甘肃老虎山段为例浅析走滑断裂古地震记录的完整性——兼论古地震研究的若干问题.地质通报,2007,26(6):650-660 Liu jing,Xu Xiwei,Li Yanfeng et al.On the completeness of paleoseismic records of strike-slip faults:An example from the Laohushan segment of the Haiyuan fault in Gansu,China——With a discussion of several problems in the paleoearthquake study. Geological Bulletin of China,2007,26(6):650 -660
20 Druffel E R M.Pluses of rapid ventilation in the North Atlantic surface ocean during the past century.Science,1997,275:1454 -1457
21甘肃省地质局.中华人民共和国区域地质矿产报告(1:20万)——巴西幅.兰州:1973.43-45 Gansu Geological Survey.Regional Geology and Mineral Resources Report of the People's Republic of China(1:200000 )——The Sheet of Baxi.Lanzhou:1973.43 - 45
22冉永康,邓起东.大地震重复特征与平均重复间隔的取值问题.地震地质,1999,24(4):316-323 Ran Yongkang,Deng Qidong.Recurrence behavior of large earthquakes and how to take advance recurrence interval of large earthquakes.Seismology and Geology,1999,24(4):316 -323
23杜平山.则木河活动断裂带大震复发问隔.四川地震,2000, (1-2):102-118 Du Pingshan.Recurrence interval on macroearthquake along the active fault of Zemuhe.Earthquake Research in Sichuan,2000,(1 - 2):102 -118
24毛凤英,张培震.古地震研究的逐次限定法与新疆北部主要断裂带的古地震研究.A-活动断裂研究(4).北京:地震出版社, 1995.153-164 Mao Fengying,Zhang Peizhen.Method for progressive constraint for paleoseismic events and paleoseismological study of major fault zone in northern Xinjiang.A-Research on Active Faults(4 ).Beijing: Seismological Press,1995.153 - 164
25何文贵,熊振,袁道阳等.东昆仑断裂带东段玛曲断裂古地震初步研究.中国地震,2006,22(2):126-134 He Wengui,Xiong Zhen,Yuan Daoyang et al.Palaeo-earthquake study on the Maqu Fault of East Kunlun active fault.Earthquake Research in China,2006,22(2):126 - 134
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