侧向侵蚀相关的走滑断裂滑动速率计算新方法
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摘要
断层滑动速率是活动构造研究中的重要内容,是反映断裂活动性和地震危险性的重要参数之一。随着测年技术不断发展和测年精度大幅度提高,全新世甚至千年尺度和百年尺度的年轻地质体的位错也越来越多地被用于断层滑动速率计算。用走滑断裂带上地质体实测年龄计算滑动速率,会受到2种因素影响:1)累积位移时间是否与所测地质体年代相符合;2)地质体位移形成过程中会受到侵蚀。在利用全新世地质体计算断层滑动速率时,应将侧向侵蚀的影响剔除。因此,文中提出1种计算走滑断层滑动速率的新方法——差值法。走滑断层上河流阶地演化与断层位错分析表明,在阶地拔河高度存在较大差异的情况下,可以利用阶地拔河高度与年龄按比例进行计算。此方法在一定程度上提高了所计算滑动速率的精度,但是需要至少有3级不同阶地的拔河高度、年龄以及位错信息。若阶地拔河高度近似呈等差排列,即各级阶地上侧向侵蚀量近似相等的情况下,利用高-低阶地累积位错量之差与对应阶地年龄差来计算滑动速率,可以在一定程度上减少上述2种因素对滑动速率的影响。应用差值法计算得到阿尔金与昆仑断裂的滑动速率为4.7~8.8mm/a,与前人获得的地质学滑动速率、测地学滑动速率、缩短速率以及强震复发周期结果一致。
Fault slip rate is one of the most important subjects in active tectonics research,which reveals the activity and seismic potential of a fault. Due to the improvement of dating precision with the development of dating methods,Holocene geological markers,even the young markers of thousands or hundreds years old,are widely used in fault slip rate calculation. Usually,in strike-slip fault slip rate calculation,there are two types of uncertainties. The first is correspondence of the offset and accumulation time; the second is the lateral erosion of the accumulated offset. In this paper,we suggest that the effect of lateral erosion of the accumulated offset should be removed. We also propose a new method for determining slip rate of strike-slip fault—the differential method. According to analyses of river terrace evolution and displacements accumulation,terrace heights( relative height above river),corresponding ages and measured offsets on the terraces are correlated to each other.We could use the terrace height,corresponding ages and the measured offsets to calculate the offsets that could be used to obtain the fault slip rate. Usually,the heights,ages and offsets of at least three terrace levels are needed in this method. If the terrace height is graded in order,the lateral erosion to each terrace is almost the same. Consequently,direct difference of offset and corresponding ages of the terraces could be used to calculate the fault slip rate. This kind of differential method could avoid the uncertainties from the lateral erosion in fault slip rate determination. By applying the differential method,we got the revised slip rates of 4. 7 ~ 8. 8mm / a on the Altyn Tagh and Kunlun Faults. These low slip rates could fit previous geodetic and geological fault slip rates,shortening rates as well as the millennial recurrence intervals of strong earthquakes along the major segments of these faults.
Fault slip rate is one of the most important subjects in active tectonics research,which reveals the activity and seismic potential of a fault. Due to the improvement of dating precision with the development of dating methods,Holocene geological markers,even the young markers of thousands or hundreds years old,are widely used in fault slip rate calculation. Usually,in strike-slip fault slip rate calculation,there are two types of uncertainties. The first is correspondence of the offset and accumulation time; the second is the lateral erosion of the accumulated offset. In this paper,we suggest that the effect of lateral erosion of the accumulated offset should be removed. We also propose a new method for determining slip rate of strike-slip fault—the differential method. According to analyses of river terrace evolution and displacements accumulation,terrace heights( relative height above river),corresponding ages and measured offsets on the terraces are correlated to each other.We could use the terrace height,corresponding ages and the measured offsets to calculate the offsets that could be used to obtain the fault slip rate. Usually,the heights,ages and offsets of at least three terrace levels are needed in this method. If the terrace height is graded in order,the lateral erosion to each terrace is almost the same. Consequently,direct difference of offset and corresponding ages of the terraces could be used to calculate the fault slip rate. This kind of differential method could avoid the uncertainties from the lateral erosion in fault slip rate determination. By applying the differential method,we got the revised slip rates of 4. 7 ~ 8. 8mm / a on the Altyn Tagh and Kunlun Faults. These low slip rates could fit previous geodetic and geological fault slip rates,shortening rates as well as the millennial recurrence intervals of strong earthquakes along the major segments of these faults.
引文
邓起东,张培震,冉勇康,等.2002.中国活动构造基本特征[J].中国科学(D辑),32:1021—1030.DENG Qi-dong,ZHANG Pei-zhen,RAN Yong-kang,et al.2002.Basic characteristics of active tectonics of China[J].Science in China(Ser D),46(4):356—372.
丁国瑜.1982.活动走滑断裂带的断错水系与地震[J].地震,1:1—10.DING Gou-yu.1982.Stream offsets of strike-slip faulting and earthquakes[J].Earthquake,1:1—10(in Chinese).
丁国瑜.1993.宁夏中卫沙坡头黄河位错现象[J].第四纪研究,4:370—378.DING Gou-yu.1993.Displacement of the Yellow River at Shapotou,Ningxia Hui Autonomous Region[J].Quaternary Sciences,4:370—387(in Chinese).
闻学泽.1991.活断层的定量研究与长期地震潜势的概率估计问题[A].国家地震局地质研究所编.活动断裂研究(1).北京:地震出版社.WEN Xue-ze.1991.Quantitative studies of active faults and assessments of their earthquake potentials[A].In:Institute of Geology,SSB(ed).Researches on Active Faults(1)[M].Seismological Press,Beijing(in Chinese).
闻学泽.1993.准时间可预报复发行为与断裂带分段概率估计[J].中国地震,9(4):289—330.WEN Xue-ze.1993.Earthquake potential assessments on the bases of quasi-time predictable recurrences ofearthquakes and fault segmentation[J].Earthquake Research in China,9(4):289—330(in Chinese).
新疆维吾尔自治区地震局.1992.阿尔金活动断裂带[M].北京:地震出版社.Xinjiang Seismological Bureau of China.1992.The Altyn Tagh Active Fault System[M].Seismological Press,Beijing(in Chinese).
张培震,李传友,毛凤英.2008.河流阶地演化与走滑断裂滑动速率[J].地震地质,30:44—57.ZHANG Pei-zhen,LI Chuan-you,MAO Feng-ying.2008.Strath terrace formation and strike-slip faulting[J].Seismology and Geology,30:44—57(in Chinese).
Bendick R,Bilham R,Freymueller J,et al.2000.Geodetic evidence for a low slip rate in the Altyn Tagh Fault[J].Nature,44:69—72.
Cowgill E.2007.Impact of riser reconstructions on estimation of secular variation in rates of strike-slip faulting:Revisiting the Cherchen River site along the Altyn Tagh Fault,NW China[J].Earth and Planetary ScienceLetters,254:239—255.
England P C,Houseman G A.1988.The mechanics of the Tibetan plateau[J].Philosophical Transactions of theRoyal Society of London(Ser A),326:301—320.
Field E H.2007.A summary of previous working groups on California earthquake probabilities[J].Bulletin ofSeismological Society of America,97:1033—1053.
Guo J,Lin A,Maruyama T,et al.2006.New constraints on recent large earthquakes along the Xidata-Dongdatansegment of the Kunlun Fault,western China[J].Bulletin of the Seismological Society of America,96:48—58.
Guo J,Lin A,Sun G,et al.2007.Surface ruptures associated with the 1937 M7.5 Tuosuo Lake and the 1963 M7.0Alake Lake earthquakes and the paleoseismicity along the Tuosuo Lake segment of the Kunlun Fault,northernTibet[J].Bulletin of the Seismological Society of America,97:474—496.
Gold R D,Cowgill E,Arrowsmith J R,et al.2009.Riser diachroneity,lateral erosion,and uncertainty in rates ofstrike-slip faulting:A case study from Tuzidun along the Altyn Tagh Fault,NW China[J].Journal ofGeophysical Research,114:B4,B04401.doi:10.1029/2008JB005913.
Kirby E,Harkins N,Wang E,et al.2007.Slip rate gradients along the eastern Kunlun Fault[J].Tectonics,26:TC2010.doi:10.1029/2006TC002033.
Lin A,Guo J.2008.Nonuniform slip rate and millennial recurrence interval of large earthquakes along the easternsegment of the Kunlun Fault,Northern Tibet[J].Bulletin of the Seismological Society of America,98:2866—2878.
Mériaux A S,Ryerson F J,Tapponnier P,et al.2004.Rapid slip along the central Altyn Tagh Fault:Morphochronologic evidence from Cherchen He and Sulamu Tagh[J].Journal of Geophysical Research,109:B06401.doi:06410.01029/02003JB002558.
Mériaux A S,Tapponnier P,Ryerson F J,et al.2005.The Aksay segment of the northern Altyn Tagh Fault:Tectonicgeomorphology,landscape evolution and Holocene slip rate[J].Journal of Geophysical Research,110:B04404.doi:04410.01029/02004JB003210.
Molnar P.1979.Earthquake recurrence intervals and plate tectonics[J].Bulletin of the Seismological Society ofAmerica,69:115—134.
Molnar P,Tapponnier P.1975.Cenozoic tectonics of Asia:Effects of a continental collision[J].Science,189:419—426.
Peltzer G,Tapponnier P.1988.Formation and evolution of strike-slip faults,rifts and basins during the India-Asiacollision:An experimental approach[J].Journal of Geophysical Research,93:15085—15117.
Peltzer G,Tapponnier P,Armijo R.1989.Magnitude of late Quaternary left-lateral displacements along the north edgeof Tibet[J].Science,246:1285—1289.
Ren Z K,Zhang Z Q,Chen T,et al.2013.Theoretical and quantitative analyses of the fault slip rate uncertaintiesfrom single event and erosion of the accumulated offset[J].Island Arc,22:185—196.
Shen Z K,Wang M,Li Y X,et al.2001.Crustal deformation along the Altyn Tagh Fault system,western China,from GPS[J].Journal of Geophysical Research,16:30607—30621.
Shen Z K,Lu J N,Wang M,et al.2005.Contemporary crustal deformation around the southeast borderland of theTibetan plateau[J].Journal of Geophysical Research,110:B11409.doi:10.1029/2004JB003421.
Tapponnier P,Xu Z Q,Roger F,et al.2001a.Oblique stepwise rise and growth of the Tibet Plateau[J].Science,294:1671—1677.
Tapponnier P,Ryerson F J,Van der Woerd J,et al.2001b.Long-term slip rates and characteristic slip:Keys toactive fault behavior and earthquake hazard[J].C R Acad Sci Paris,Sciences de la Terre et des Planets Earthand Planetary Sciences,333:483—494.
Van Der Woerd J,Ryerson F J,Tapponnier P,et al.1998.Holocene left-slip rate determined by cosmogenic surfacedating on the Xidatan segment of the Kunlun Fault(Qinghai,China)[J].Geology,26(8):695—698.
Van der Woerd J,Tapponnier P,Ryerson F J,et al.2002.Uniform postglacial slip-rate along the central 600km ofthe Kunlun Fault(Tibet),from26Al,10Be,14C dating of riser offsets and climatic origin of the regional morphology[J].Geophysical Journal International,148:356—388.
Wallace R T.1987.Grouping and migration of surface faulting and variations in slip rates on faults in the Great BasinProvince[J].Bulletin of the Seismological Society of America,77:868—876.
Wallace K,Yin G,Bilham R.2004.Inescapable low slip on the Altyn Tagh Fault[J].Geophysical ResearchLetters,31:L09613.doi:10.1029/2004GL019724.
Washburn Z,Arrowsmith J R,Forman S L,et al.2001.Late Holocene earthquake history of the central Altyn TaghFault,China[J].Geology,29:1051—1054.
Washburn Z,Arrowsmith J R,Dupont-Nivet G,et al.2003.Paleoseismology of the Xorxol segment of the centralAltyn Tagh Fault,Xinjiang,China[J].Annuals of geophysics,46:1015—1034.
Zhang P Z,Molnar P,Xu X W.2007.Late Quaternary and present-day rates of slip along the Altyn Tagh Fault,northern margin of the Tibetan plateau[J].Tectonics,26:TC5010.doi:10.1029/2006TC002014.
Zhang P Z,Shen Z K,Wang M,et al.2004.Continuous deformation of the Tibet Plateau from global positioningsystem data[J].Geology,32:809—812.
丁国瑜.1982.活动走滑断裂带的断错水系与地震[J].地震,1:1—10.DING Gou-yu.1982.Stream offsets of strike-slip faulting and earthquakes[J].Earthquake,1:1—10(in Chinese).
丁国瑜.1993.宁夏中卫沙坡头黄河位错现象[J].第四纪研究,4:370—378.DING Gou-yu.1993.Displacement of the Yellow River at Shapotou,Ningxia Hui Autonomous Region[J].Quaternary Sciences,4:370—387(in Chinese).
闻学泽.1991.活断层的定量研究与长期地震潜势的概率估计问题[A].国家地震局地质研究所编.活动断裂研究(1).北京:地震出版社.WEN Xue-ze.1991.Quantitative studies of active faults and assessments of their earthquake potentials[A].In:Institute of Geology,SSB(ed).Researches on Active Faults(1)[M].Seismological Press,Beijing(in Chinese).
闻学泽.1993.准时间可预报复发行为与断裂带分段概率估计[J].中国地震,9(4):289—330.WEN Xue-ze.1993.Earthquake potential assessments on the bases of quasi-time predictable recurrences ofearthquakes and fault segmentation[J].Earthquake Research in China,9(4):289—330(in Chinese).
新疆维吾尔自治区地震局.1992.阿尔金活动断裂带[M].北京:地震出版社.Xinjiang Seismological Bureau of China.1992.The Altyn Tagh Active Fault System[M].Seismological Press,Beijing(in Chinese).
张培震,李传友,毛凤英.2008.河流阶地演化与走滑断裂滑动速率[J].地震地质,30:44—57.ZHANG Pei-zhen,LI Chuan-you,MAO Feng-ying.2008.Strath terrace formation and strike-slip faulting[J].Seismology and Geology,30:44—57(in Chinese).
Bendick R,Bilham R,Freymueller J,et al.2000.Geodetic evidence for a low slip rate in the Altyn Tagh Fault[J].Nature,44:69—72.
Cowgill E.2007.Impact of riser reconstructions on estimation of secular variation in rates of strike-slip faulting:Revisiting the Cherchen River site along the Altyn Tagh Fault,NW China[J].Earth and Planetary ScienceLetters,254:239—255.
England P C,Houseman G A.1988.The mechanics of the Tibetan plateau[J].Philosophical Transactions of theRoyal Society of London(Ser A),326:301—320.
Field E H.2007.A summary of previous working groups on California earthquake probabilities[J].Bulletin ofSeismological Society of America,97:1033—1053.
Guo J,Lin A,Maruyama T,et al.2006.New constraints on recent large earthquakes along the Xidata-Dongdatansegment of the Kunlun Fault,western China[J].Bulletin of the Seismological Society of America,96:48—58.
Guo J,Lin A,Sun G,et al.2007.Surface ruptures associated with the 1937 M7.5 Tuosuo Lake and the 1963 M7.0Alake Lake earthquakes and the paleoseismicity along the Tuosuo Lake segment of the Kunlun Fault,northernTibet[J].Bulletin of the Seismological Society of America,97:474—496.
Gold R D,Cowgill E,Arrowsmith J R,et al.2009.Riser diachroneity,lateral erosion,and uncertainty in rates ofstrike-slip faulting:A case study from Tuzidun along the Altyn Tagh Fault,NW China[J].Journal ofGeophysical Research,114:B4,B04401.doi:10.1029/2008JB005913.
Kirby E,Harkins N,Wang E,et al.2007.Slip rate gradients along the eastern Kunlun Fault[J].Tectonics,26:TC2010.doi:10.1029/2006TC002033.
Lin A,Guo J.2008.Nonuniform slip rate and millennial recurrence interval of large earthquakes along the easternsegment of the Kunlun Fault,Northern Tibet[J].Bulletin of the Seismological Society of America,98:2866—2878.
Mériaux A S,Ryerson F J,Tapponnier P,et al.2004.Rapid slip along the central Altyn Tagh Fault:Morphochronologic evidence from Cherchen He and Sulamu Tagh[J].Journal of Geophysical Research,109:B06401.doi:06410.01029/02003JB002558.
Mériaux A S,Tapponnier P,Ryerson F J,et al.2005.The Aksay segment of the northern Altyn Tagh Fault:Tectonicgeomorphology,landscape evolution and Holocene slip rate[J].Journal of Geophysical Research,110:B04404.doi:04410.01029/02004JB003210.
Molnar P.1979.Earthquake recurrence intervals and plate tectonics[J].Bulletin of the Seismological Society ofAmerica,69:115—134.
Molnar P,Tapponnier P.1975.Cenozoic tectonics of Asia:Effects of a continental collision[J].Science,189:419—426.
Peltzer G,Tapponnier P.1988.Formation and evolution of strike-slip faults,rifts and basins during the India-Asiacollision:An experimental approach[J].Journal of Geophysical Research,93:15085—15117.
Peltzer G,Tapponnier P,Armijo R.1989.Magnitude of late Quaternary left-lateral displacements along the north edgeof Tibet[J].Science,246:1285—1289.
Ren Z K,Zhang Z Q,Chen T,et al.2013.Theoretical and quantitative analyses of the fault slip rate uncertaintiesfrom single event and erosion of the accumulated offset[J].Island Arc,22:185—196.
Shen Z K,Wang M,Li Y X,et al.2001.Crustal deformation along the Altyn Tagh Fault system,western China,from GPS[J].Journal of Geophysical Research,16:30607—30621.
Shen Z K,Lu J N,Wang M,et al.2005.Contemporary crustal deformation around the southeast borderland of theTibetan plateau[J].Journal of Geophysical Research,110:B11409.doi:10.1029/2004JB003421.
Tapponnier P,Xu Z Q,Roger F,et al.2001a.Oblique stepwise rise and growth of the Tibet Plateau[J].Science,294:1671—1677.
Tapponnier P,Ryerson F J,Van der Woerd J,et al.2001b.Long-term slip rates and characteristic slip:Keys toactive fault behavior and earthquake hazard[J].C R Acad Sci Paris,Sciences de la Terre et des Planets Earthand Planetary Sciences,333:483—494.
Van Der Woerd J,Ryerson F J,Tapponnier P,et al.1998.Holocene left-slip rate determined by cosmogenic surfacedating on the Xidatan segment of the Kunlun Fault(Qinghai,China)[J].Geology,26(8):695—698.
Van der Woerd J,Tapponnier P,Ryerson F J,et al.2002.Uniform postglacial slip-rate along the central 600km ofthe Kunlun Fault(Tibet),from26Al,10Be,14C dating of riser offsets and climatic origin of the regional morphology[J].Geophysical Journal International,148:356—388.
Wallace R T.1987.Grouping and migration of surface faulting and variations in slip rates on faults in the Great BasinProvince[J].Bulletin of the Seismological Society of America,77:868—876.
Wallace K,Yin G,Bilham R.2004.Inescapable low slip on the Altyn Tagh Fault[J].Geophysical ResearchLetters,31:L09613.doi:10.1029/2004GL019724.
Washburn Z,Arrowsmith J R,Forman S L,et al.2001.Late Holocene earthquake history of the central Altyn TaghFault,China[J].Geology,29:1051—1054.
Washburn Z,Arrowsmith J R,Dupont-Nivet G,et al.2003.Paleoseismology of the Xorxol segment of the centralAltyn Tagh Fault,Xinjiang,China[J].Annuals of geophysics,46:1015—1034.
Zhang P Z,Molnar P,Xu X W.2007.Late Quaternary and present-day rates of slip along the Altyn Tagh Fault,northern margin of the Tibetan plateau[J].Tectonics,26:TC5010.doi:10.1029/2006TC002014.
Zhang P Z,Shen Z K,Wang M,et al.2004.Continuous deformation of the Tibet Plateau from global positioningsystem data[J].Geology,32:809—812.
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