小型拉分盆地的生长与走滑断层的位移速率——以青藏高原东南缘则木河断裂带为例
|
摘要
活动断层滑动速率可以用来定量比较不同断裂带或同一断裂带不同时段的活动性,同时还是地震危险性评价的重要参数,合理评估活动断层的滑动速率主要受限于两个参数的可靠性,即断层的累积位移量和相应的活动时间。传统上较理想的用于评估走滑断层滑动速率的地貌体一般为阶地、冲洪积扇、冲沟等的位错测量和相应活动累积时间的确定,文中则尝试通过青藏高原东南缘则木河断裂带大箐梁子段三维组合探槽揭示的小型三角状拉分盆地的生长模式来约束断层的水平位移速率,基于野外详细的调查、拉分盆地底部14C测年以及实时差分GPS精确测量,约束了则木河断裂带全新世以来的断层平均左旋滑动速率为(2.4±0.2)～3.6mm/a,这比前人给出的滑动速率偏小,但却与古地震资料及GPS观测结果吻合得较好。
Slip rate of active faults is deterministic to compare active earthquake behaviors among different faults or different segments along a fault,and also it is a key parameter for seismic hazard assessment.Geologically reliable estimation on slip rate is subject to two active tectonic parameters,the cumulative displacement produced by multiple surface-rupturing seismic events and the corresponding true ages,respectively.Generally,for strike-slip faults,we carefully measure geomorphic expressions,such as deformation or offset produced by multiple faulting on river terrace,alluvial-fluvial fans or gullies,and then integrate geochronological constraint from dating on these geomorphic expressions.Based on the above two crucial parameters,we further determine slip rates along faults.However,this paper is attempted to use another deformation of geomorphic expression,a growth model for a small triangular pull-apart basin(sag pond),to constrain fault slip rate at the Daqingliangzi section of Zemuhe Fault on the southeastern margin of the Tibetan Plateau.Based on several three-dimension trench excavations,reliable radiocarbon dating at the bottom of stratigraphic unit in the triangular pull-apart basin(sag pond),detailed field investigation along the Daqingliangzi section of Zemuhe Fault and accurate RTK(GPS)survey,we suggest that Holocene average left-lateral slip rate of the Zemuhe Fault is constrained between 2.4±0.2mm/a and 3.6mm/a,which is a little smaller than those estimated by other geoscientists,however this strike-slip rate is much more accordant with paleoseismic recurrence behaviors and present velocity field obtained from GPS measurement across the Zemuhe Fault.
Slip rate of active faults is deterministic to compare active earthquake behaviors among different faults or different segments along a fault,and also it is a key parameter for seismic hazard assessment.Geologically reliable estimation on slip rate is subject to two active tectonic parameters,the cumulative displacement produced by multiple surface-rupturing seismic events and the corresponding true ages,respectively.Generally,for strike-slip faults,we carefully measure geomorphic expressions,such as deformation or offset produced by multiple faulting on river terrace,alluvial-fluvial fans or gullies,and then integrate geochronological constraint from dating on these geomorphic expressions.Based on the above two crucial parameters,we further determine slip rates along faults.However,this paper is attempted to use another deformation of geomorphic expression,a growth model for a small triangular pull-apart basin(sag pond),to constrain fault slip rate at the Daqingliangzi section of Zemuhe Fault on the southeastern margin of the Tibetan Plateau.Based on several three-dimension trench excavations,reliable radiocarbon dating at the bottom of stratigraphic unit in the triangular pull-apart basin(sag pond),detailed field investigation along the Daqingliangzi section of Zemuhe Fault and accurate RTK(GPS)survey,we suggest that Holocene average left-lateral slip rate of the Zemuhe Fault is constrained between 2.4±0.2mm/a and 3.6mm/a,which is a little smaller than those estimated by other geoscientists,however this strike-slip rate is much more accordant with paleoseismic recurrence behaviors and present velocity field obtained from GPS measurement across the Zemuhe Fault.
引文
邓起东,陈立春,冉勇康.2004.活动构造定量研究与应用[J].地学前缘,11(4):383—392.DENG Qi-dong,CHEN Li-chun,RAN Yong-kang.2004.Quantitative studies and applications of active tectonics[J].Earth Science Frontiers,11(4):383—392(in Chinese).
杜平山.2000.则木河断裂带的走滑位移及滑动速率[J].四川地震,1:49—64.DU Ping-shan.2000.Slip displacement and its rate along Zemuhe Faults[J].Earthquake Research in Sichuan,1:49—64(in Chinese).
冯元保,杜平山,黄玉书.2000.1850年西昌地震地表破裂带[J].四川地震,1:80—96.FENG Yuan-bao,DU Ping-shan,HUANG Yu-shu.2000.Earthquake rupture belt of1850Xichang M7.5earthquake[J].Earthquake Research in Sichuan,1:80—96(in Chinese).
冉勇康,陈立春,程建武,等.2008.安宁河断裂冕宁以北晚第四纪地表变形与强震破裂行为[J].中国科学(D辑),38(5):543—554.RAN Yong-kang,CHEN Li-chun,CHENG Jian-wu,et al.2008.Late Quaternary surface deformation and rupture behavior of strong earthquake on the segment north of Mianning of the Anninghe Fault[J].Science in China(Ser D),51(9):1224—1237.
任金卫.1994.则木河断裂晚第四纪位移及滑动速率[J].地震地质,16(2):146.REN Jin-wei.1994.Late Quaternary displacement and slip rate of Zemuhe Fault in Sichuan,China[J].Seismology andGeology,16(2):146(in Chinese).
任金卫,李玶.1993.四川西昌1850年地震地表破裂特征研究[J].地震地质,15(2):97—106.REN Jin-wei,LI Ping.1993.The characteristics of surface faulting of the1850earthquake in Xichang,Sichuan[J].Seismology and Geology,15(2):97—106(in Chinese).
田勤俭,任志坤,张军龙.2008.则木河断裂带大箐梁子附近古地震组合探槽研究[J].地震地质,30(2):400—411.TIAN Qin-jian,REN Zhi-kun,ZHANG Jun-long.2008.Study of paleoearthquakes by combined trench on Zemuhe Faultaround Daqingliangzi,Xichang,Sichuan[J].Seismology and Geology,30(2):400—411(in Chinese).
王虎,冉勇康,李彦宝,等.2011.活动走滑断裂古地震破裂与小型三角状拉分盆地演化[J].中国科学(D辑),已提交.WANG Hu,RAN Yong-kang,LI Yan-bao,et al.2011.Paleoseismic rupturing and evolution of small triangular pull-apartbasin on active strike-slip fault[J].Science in China(Ser D),in press.
王阎昭,王恩宁,沈正康,等.2008.基于GPS资料约束反演川滇地区主要断裂现今活动速率[J].中国科学(D辑),38(5):582—597.WANG Yan-zhao,WANG En-ning,SHEN Zheng-kang,et al.,2008.GPS-constrained inversion of present-day slip ratesalong major fault of the Sichuan-Yunnan region,China[J].Science in China(Ser D),51(9):1267—1283.
闻学泽,杜平山,龙德雄.2000.安宁河断裂带小相岭段古地震的新证据及最晚事件的年代[J].地震地质,22(1):1—8.WEN Xue-ze,DU Ping-shan,LONG De-xiong.2000.New evidence of paleoearthquakes and date of the latest event on the Xiaoxiangling mountain segment of the Anninghe Fault zone[J].Seismology and Geology,22(1):1—8(in Chinese).
闻学泽,范军,易桂喜,等.2008.川西安宁河断裂上的地震空区[J].中国科学(D辑),38(7):797—807.WEN Xue-ze,FAN Jun,YI Gui-xi,et al.2008.A seismic gap on the Anninghe Fault in western Sichuan,China[J].Science in China(Ser D),51(10):1375—1387.
闻学泽,马胜利,雷兴林,等.2007.安宁河-则木河断裂带过渡段及其附近新发现的历史大地震破裂遗迹[J].地震地质,29(4):826—833.WEN Xue-ze,MA Sheng-li,LEI Xing-lin,et al.2007.Newly found surface rupture remains of large historical earthquakes on and near the transition segment of the Anninghe and Zemuhe Fault zones[J].Seismology and Geology,29(4):826—833(in Chinese).
俞维贤,宋方敏,闻学泽,等.2001.1850年西昌地震地表破裂带的考察研究[J].地震研究,24(4):346—350.YU Wei-xian,SONG Fang-min,WEN Xue-ze,et al.2001.Study of the surface rupture zone of Xichang earthquake in1850[J].Journal of Seismological Research,24(4):346—350(in Chinese).
Alper G.2010.Geometric characteristics of pull-apart basins[J].Lithosphere,2(3):199—206.
He Honglin,Ren Jinwei.2003.Holocene earthquakes on the Zemuhe Fault in southwestern China[J].Annals of Geophysics,46(5):1035—1051.
He Honglin,Takashi Oguchi.2008.Late Quaternary activity of the Zemuhe and Xiaojiang Faults in southwest Chinafrom geomorphological mapping[J].Geomorphology,96(1-2):62—85.
Peltzer G,Tapponnier P.1988.Formation and evolution of strike-slip faults,rifts,and basins during the India-Asia collision:An experiment approach[J].Journal of Geophysical Research,93(B12):15085—15117.
Ren Zhikun,Lin Aiming,RAO Gang.2010a.Late Pleistocene-Holocene activity of the Zemuhe Fault on the southeasternmargin of the Tibetan Plateau[J].Tectonophysics,495(3-4):324—336.
Ren Zhikun,Lin Aiming.2010b.Deformation characteristics of co-seismic surface ruptures produced by the1850M7.5Xichang earthquake on the eastern margin of the Tibetan Plateau[J].Journal of Asian Earth Sciences,38(1-2):1—13.
Shen Zhengkang,Lu Jiangning,Wang Min,et al.2005.Contemporary crustal deformation around the southeast borderland of the Tibetan Plateau[J].Journal of Geophysical Research,110(B11409).doi:10.1029/2004JB003421.
Tapponnier P,Peltzer G,Le Dain A Y.et al.1982.Propagating extrusion tectonics in Asia:New insights from simpleexperiments with plasticine[J].Geology,10(12):611—616.
Tapponnier P,Xu Zhiqin,Roger F,et al.2001.Oblique stepwise rise and growth of the Tibet plateau[J].Science,294(5547):1671—1677.
Wen Xueze,Ma Shengli,Xu Xiwei,et al.2008.Historical pattern and behavior of earthquake ruptures along the easternboundary of the Sichuan-Yunnan faulted-block,southwestern China[J].Physics of the Earth and Planetary Interiors,168(1-2):16—36.
Wang Hu,Ran Yongkang,Li Yanbao,et al.2011.Holocene paleoseismologic record of large,infrequent earthquakes onthe Zemuhe Fault on the southeastern margin of the Tibetan Plateau[J].The Geological Society of America Bulle-tin,submitted.
Zhang Peizhen,Sheng Zhengkang,Wang Min,et al.2004.Continuous deformation of the Tibetan Plateau from global positioning system data[J].Geology,32(9):809—812.
杜平山.2000.则木河断裂带的走滑位移及滑动速率[J].四川地震,1:49—64.DU Ping-shan.2000.Slip displacement and its rate along Zemuhe Faults[J].Earthquake Research in Sichuan,1:49—64(in Chinese).
冯元保,杜平山,黄玉书.2000.1850年西昌地震地表破裂带[J].四川地震,1:80—96.FENG Yuan-bao,DU Ping-shan,HUANG Yu-shu.2000.Earthquake rupture belt of1850Xichang M7.5earthquake[J].Earthquake Research in Sichuan,1:80—96(in Chinese).
冉勇康,陈立春,程建武,等.2008.安宁河断裂冕宁以北晚第四纪地表变形与强震破裂行为[J].中国科学(D辑),38(5):543—554.RAN Yong-kang,CHEN Li-chun,CHENG Jian-wu,et al.2008.Late Quaternary surface deformation and rupture behavior of strong earthquake on the segment north of Mianning of the Anninghe Fault[J].Science in China(Ser D),51(9):1224—1237.
任金卫.1994.则木河断裂晚第四纪位移及滑动速率[J].地震地质,16(2):146.REN Jin-wei.1994.Late Quaternary displacement and slip rate of Zemuhe Fault in Sichuan,China[J].Seismology andGeology,16(2):146(in Chinese).
任金卫,李玶.1993.四川西昌1850年地震地表破裂特征研究[J].地震地质,15(2):97—106.REN Jin-wei,LI Ping.1993.The characteristics of surface faulting of the1850earthquake in Xichang,Sichuan[J].Seismology and Geology,15(2):97—106(in Chinese).
田勤俭,任志坤,张军龙.2008.则木河断裂带大箐梁子附近古地震组合探槽研究[J].地震地质,30(2):400—411.TIAN Qin-jian,REN Zhi-kun,ZHANG Jun-long.2008.Study of paleoearthquakes by combined trench on Zemuhe Faultaround Daqingliangzi,Xichang,Sichuan[J].Seismology and Geology,30(2):400—411(in Chinese).
王虎,冉勇康,李彦宝,等.2011.活动走滑断裂古地震破裂与小型三角状拉分盆地演化[J].中国科学(D辑),已提交.WANG Hu,RAN Yong-kang,LI Yan-bao,et al.2011.Paleoseismic rupturing and evolution of small triangular pull-apartbasin on active strike-slip fault[J].Science in China(Ser D),in press.
王阎昭,王恩宁,沈正康,等.2008.基于GPS资料约束反演川滇地区主要断裂现今活动速率[J].中国科学(D辑),38(5):582—597.WANG Yan-zhao,WANG En-ning,SHEN Zheng-kang,et al.,2008.GPS-constrained inversion of present-day slip ratesalong major fault of the Sichuan-Yunnan region,China[J].Science in China(Ser D),51(9):1267—1283.
闻学泽,杜平山,龙德雄.2000.安宁河断裂带小相岭段古地震的新证据及最晚事件的年代[J].地震地质,22(1):1—8.WEN Xue-ze,DU Ping-shan,LONG De-xiong.2000.New evidence of paleoearthquakes and date of the latest event on the Xiaoxiangling mountain segment of the Anninghe Fault zone[J].Seismology and Geology,22(1):1—8(in Chinese).
闻学泽,范军,易桂喜,等.2008.川西安宁河断裂上的地震空区[J].中国科学(D辑),38(7):797—807.WEN Xue-ze,FAN Jun,YI Gui-xi,et al.2008.A seismic gap on the Anninghe Fault in western Sichuan,China[J].Science in China(Ser D),51(10):1375—1387.
闻学泽,马胜利,雷兴林,等.2007.安宁河-则木河断裂带过渡段及其附近新发现的历史大地震破裂遗迹[J].地震地质,29(4):826—833.WEN Xue-ze,MA Sheng-li,LEI Xing-lin,et al.2007.Newly found surface rupture remains of large historical earthquakes on and near the transition segment of the Anninghe and Zemuhe Fault zones[J].Seismology and Geology,29(4):826—833(in Chinese).
俞维贤,宋方敏,闻学泽,等.2001.1850年西昌地震地表破裂带的考察研究[J].地震研究,24(4):346—350.YU Wei-xian,SONG Fang-min,WEN Xue-ze,et al.2001.Study of the surface rupture zone of Xichang earthquake in1850[J].Journal of Seismological Research,24(4):346—350(in Chinese).
Alper G.2010.Geometric characteristics of pull-apart basins[J].Lithosphere,2(3):199—206.
He Honglin,Ren Jinwei.2003.Holocene earthquakes on the Zemuhe Fault in southwestern China[J].Annals of Geophysics,46(5):1035—1051.
He Honglin,Takashi Oguchi.2008.Late Quaternary activity of the Zemuhe and Xiaojiang Faults in southwest Chinafrom geomorphological mapping[J].Geomorphology,96(1-2):62—85.
Peltzer G,Tapponnier P.1988.Formation and evolution of strike-slip faults,rifts,and basins during the India-Asia collision:An experiment approach[J].Journal of Geophysical Research,93(B12):15085—15117.
Ren Zhikun,Lin Aiming,RAO Gang.2010a.Late Pleistocene-Holocene activity of the Zemuhe Fault on the southeasternmargin of the Tibetan Plateau[J].Tectonophysics,495(3-4):324—336.
Ren Zhikun,Lin Aiming.2010b.Deformation characteristics of co-seismic surface ruptures produced by the1850M7.5Xichang earthquake on the eastern margin of the Tibetan Plateau[J].Journal of Asian Earth Sciences,38(1-2):1—13.
Shen Zhengkang,Lu Jiangning,Wang Min,et al.2005.Contemporary crustal deformation around the southeast borderland of the Tibetan Plateau[J].Journal of Geophysical Research,110(B11409).doi:10.1029/2004JB003421.
Tapponnier P,Peltzer G,Le Dain A Y.et al.1982.Propagating extrusion tectonics in Asia:New insights from simpleexperiments with plasticine[J].Geology,10(12):611—616.
Tapponnier P,Xu Zhiqin,Roger F,et al.2001.Oblique stepwise rise and growth of the Tibet plateau[J].Science,294(5547):1671—1677.
Wen Xueze,Ma Shengli,Xu Xiwei,et al.2008.Historical pattern and behavior of earthquake ruptures along the easternboundary of the Sichuan-Yunnan faulted-block,southwestern China[J].Physics of the Earth and Planetary Interiors,168(1-2):16—36.
Wang Hu,Ran Yongkang,Li Yanbao,et al.2011.Holocene paleoseismologic record of large,infrequent earthquakes onthe Zemuhe Fault on the southeastern margin of the Tibetan Plateau[J].The Geological Society of America Bulle-tin,submitted.
Zhang Peizhen,Sheng Zhengkang,Wang Min,et al.2004.Continuous deformation of the Tibetan Plateau from global positioning system data[J].Geology,32(9):809—812.