中国大陆古地震研究的关键技术与案例解析(4)——古地震定年技术的样品采集和事件年代分析
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摘要
古地震资料要在地震中长期预报和地震危险性评估中发挥更重要的作用,关键在于减小古地震研究中的不确定性,古地震发生年代的确定是最大限度减小不确定性的关键因素之一。要得到尽可能接近真实的古地震事件年代,除正确地选择测年方法外,正确的采样方法和事件年代确定技术尤为关键。在几种主要测年技术中,优先采集碳十四(14C)测年样品、释光样品采集搬运过程有充分"退火"条件的物质、铍十(10Be)样品应采集各种干扰因素较少的样品、依据构造运动属性选择适宜的采样位置、用序列样品限制事件年代等,是正确采集测定事件年代样品的技术要点;用地层年代限制的事件发生年代宜用区间值、有多个可信样品年龄值时应用年轻样品的年代数据,是确定单一地点事件发生年代的基本原则;而包括逐次限定法、Z统计法、年龄分布曲线重叠法、事件窗法、年龄分布曲线权重重叠法在内的时间对比法,以及空间对比法是断层或断层段多个测年地点事件年代估计的主要分析方法。
Lowering uncertainties of paleoseismic data is very important,which facilitates medium and longterm earthquake prediction and seismic risk assessment in paleoseismic studies. Among these uncertainties,paleoseismic timing is highly focused and its constraint is one of the most key factors in lowering uncertainties. To get the age as true as possible,choosing right dating,sampling methods and techniques on event ages are essential. Among the several primary dating techniques,radiocarbon dating is prior to the other methods. We should choose material that is breached completely during transportation for OSL dating,and samples that are hardly affected by kinds of factors for10 Be dating.Sampling at appropriate sites based on analysis of tectonic background and using sequential ages to constrain paleoseismic events are the primary keys of techniques on accurate event dating. Interval value is suggested for age constraint when using stratigraphic chronology. When there are multiple ages for different samples within a layer,we should choose the youngest and reliable age. These rules are recommended when constraining paleoseismic ages at a single site. Temporal and spatial correlation such as successive limit method, Z statistics, overlapping distributions likelihood approach,event window and ad hoc weighted overlap methods are the primary analysis approaches for event dating at multiple sites along faults or fault segments.
Lowering uncertainties of paleoseismic data is very important,which facilitates medium and longterm earthquake prediction and seismic risk assessment in paleoseismic studies. Among these uncertainties,paleoseismic timing is highly focused and its constraint is one of the most key factors in lowering uncertainties. To get the age as true as possible,choosing right dating,sampling methods and techniques on event ages are essential. Among the several primary dating techniques,radiocarbon dating is prior to the other methods. We should choose material that is breached completely during transportation for OSL dating,and samples that are hardly affected by kinds of factors for10 Be dating.Sampling at appropriate sites based on analysis of tectonic background and using sequential ages to constrain paleoseismic events are the primary keys of techniques on accurate event dating. Interval value is suggested for age constraint when using stratigraphic chronology. When there are multiple ages for different samples within a layer,we should choose the youngest and reliable age. These rules are recommended when constraining paleoseismic ages at a single site. Temporal and spatial correlation such as successive limit method, Z statistics, overlapping distributions likelihood approach,event window and ad hoc weighted overlap methods are the primary analysis approaches for event dating at multiple sites along faults or fault segments.
引文
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冉勇康,王虎,李彦宝,等.2012a.中国大陆古地震研究的关键技术与案例解析(1):走滑活动断裂的探槽地点、布设与事件识别标志[J].地震地质,34(2):197—210.doi:10.3969/j.issn.0253-4967.2012.02.001.RAN Yong-kang,WANG Hu,LI Yan-bao,et al.2012a.Key techniques and several cases analysis in paleoseismicstudies in mainland China(1):Trenching sites,layouts and paleoseismic indicators on active strike-slip faults[J].Seismology and Geology,34(2):197—210(in Chinese).
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冉勇康,李彦宝,杜鹏,等.2014.中国大陆古地震研究的关键技术与案例解析(3):正断层破裂特征、环境影响与古地震识别[J].地震地质,36(2):287—301.doi:10.3969/j.issn.0253-4967.2014.02.001.RAN Yong-kang,LI Yan-bao,DU Peng,et al.2014.Key techniques and several cases analysis in paleoseismicstudies in mainland China(3):Rupture characteristics,environment impact and paleoseismic indicators on normalfaults[J].Seismology and Geology,36(2):287—301(in Chinese).
冉勇康,王虎,张培震,等.2013.古地震研究的技术和方法[A].见:丁仲礼主编.固体地球科学研究方法.北京:科学出版社.258—275.RAN Yong-kang,WANG Hu,ZHANG Pei-zhen,et al.2013.Techniques and Methods of Paleoseismic Studies[A].In:DING Zhong-li(ed).Methods of Research in Solid Earth Sciences.Science Press,Beijing.258—275(inChinese).
王虎,冉勇康,李彦宝,等.2013.则木河断裂上古地震破裂与小型三角状拉分盆地演化[J].中国科学(D辑),43(7):1106—1114.WANG Hu,RAN Yong-kang,LI Yan-bao,et al.2013.Paleoseismic ruptures and evolution of a small triangular pullapart basin on the Zemuhe Fault[J].Science in China(Ser D),56(3):504—512.
徐良鑫,冉勇康,刘华国,等.2011.柯坪塔格山前层状地貌面与晚第四纪逆断层变形:以三岔口北西山前断错地貌为例[J].地震地质,33(4):777—788.doi:10.3969/j.issn.0253-4967.2011.04.004.XU Liang-xin,RAN Yong-kang,LIU Hua-guo,et al.2011.Deformation of reverse fault and layered landform inpiedmont of Kalpintag Mountains during the late Quaternary:Example from the faulted landform of northwesternSanchakou[J].Seismology and Geology,33(4):777—788(in Chinese).
杨会丽.2013.地震相关快速沉积物释光测年研究[D]:[学位论文].北京:中国地震局地质研究所.YANG Hui-li.2013.Optical dating research of rapidly deposited sediments related to earthquakes[D].Dissertation.Institute of Geology,China Earthquake Administration,Beijing(in Chinese).
Anderson R S,Repka J L,Dick G S.1996.Explicit treatment of inheritance in dating depositional surfaces using insitu10Be and26Al[J].Geology,24(1):47—51.
Bailey R M,Singarayer J S,Ward S,et al.2003.Identification of partial resetting using De as a function ofillumination time[J].Radiation Measurements,37(4-5):511—518.
Biasi G,Weldon II R J,Scharer K.2011.Rupture length and paleomagnitude estimates from point measurements ofdisplacement—A model-based approach[J].Geological Society of America Special Papers,479:195—204.
Bierman P R,Alan R G,Marc W C.1995.Cosmogenic ages for earthquake recurrence intervals and debris flow fandeposition,Owens Valley,California[J].Science,270(5235):447—450.
Brown E T,Bourlés D L,Raisbeck G M,et al.1998.Estimation of slip rates in the southern Tien Shan using cosmicray exposure dates of abandoned alluvial fans[J].Bulletin of the Geological Society of America,110(3):377—386.
Chen Li-chun,Ran Yong-kang,Wang Hu,et al.2013.Paleoseismology and kinematic characteristics of theXiaoyudong rupture,a short but significant strange segment characterized by the May 12,2008,MW7.9earthquake in Sichuan,China[J].Tectonophysics,584:91—101.
Cunha P P,Buylaert J P,Murray A S,et al.2010.Optical dating of clastic deposits generated by an extreme marinecoastal flood:The 1755 tsunami deposits in the Algarve(Portugal)[J].Quaternary Geochronology,5(2-3):329—335.
Duller G A T.2008.Single-grain optical dating of Quaternary sediments:Why aliquot size matters in luminescencedating[J].Boreas,37(4):589—612.
Galimberti M,Ramsey C B.2004.Wiggle-match dating of tree-ring sequences[J].Radiocarbon,46(2):917—924.
Godfrey-Smith D I,Huntley D J,Chen W H.1988.Optical dating studies of quartz and feldspar sediment extracts[J].Quaternary Science Reviews,7(3-4):373—380.
Hidy A J,Gosse J C,Pederson J L,et al.2010.A geologically constrained Monte Carlo approach to modelingexposure ages from profiles of cosmogenic nuclides:An example from Lees Ferry,Arizona[J].Geochemistry,Geophysics,Geosystems,11(9):Q0AA10.doi:10.1029/2010GC003084.
Lal D.1991.Cosmic ray labeling of erosion surfaces:In situ nuclide production rates and erosion models[J].Earthand Planetary Science Letters,104:424—439.
Li An,Ran Yong-kang,Xu Liangh-xin,et al.2013.Paleoseismic study of the east Kalpintage Fault in southwestTianshan based on deformation of alluvial fans and10Be dating[J].Natural Hazards,68(2):1075—1087.
Lu Yan-chou,Prescott J R,Zhao Hua,et al.2002.Optical dating of colluvial deposits from Xiyangfang,China andthe relation to palea-earthquake events[J].Quaternary Science Reviews,21(8-9):1087—1097.
Madsen A T,Murray A S,Andersen T J,et al.2007.Optical dating of young tidal sediments in the Danish WaddenSea[J].Quaternary Geochronology,2(1-4):89—94.
Mc Calpin J P.2009.Paleoseismology[M].Academic Press.
Nishiizumi K,Kohl C P,Arnold J R,et al.1993.Role of in situ cosmogenic nuclides10Be and26Al in the study ofdiverse geomorphic processes[J].Earth Surface Processes and Landforms,18:407—425.
Ran Yong-kang,Chen Li-chun,Chen Jie,et al.2010.Paleoseismic evidence and repeat time of large earthquakes atthree sites along the Longmenshan fault zone[J].Tectonophysics,491(1-4):141—153.
Ran Yong-kang,Chen Wen-shan,Xu Xi-wei,et al.2013.Paleoseismic events and recurrence interval along theBeichuan-Yingxiu Fault of Longmenshan Fault zone,Yingxiu,Sichuan,China[J].Tectonophysics,584:81—90.
Repka J L,Anderson R S,Finkel R C.1997.Cosmogenic dating of fluvial terraces,Fremont River,Utah[J].Earthand Planetary Science Letters,152(1-4):59—73.
Santos G M,Alexandre A,Coe H H G,et al.2010.The phytolith14C puzzle:A tale of background determinationsand accuracy tests[J].Radiocarbon,52(1):113—128.
Singarayer J S,Bailey R M,Ward S,et al.2005.Assessing the completeness of optical resetting of quartz OSL in thenatural environment[J].Radiation Measurements,40(1):13—25.
Stokes S,Bray H E,Blum M D.2001.Optical resetting in large drainage basins:Tests of zeroing assumptions usingsingle-aliquot procedures[J].Quaternary Science Reviews,20(5-9):879—885.
Talma A S,Vogel J C.1993.A simplified approach to calibrating14C dates[J].Radiocarbon,35(2):317—322.
Thomas P J,Reddy D V,Kumar D,et al.2007.Optical dating of liquefaction features to constrain prehistoricearthquakes in Upper Assam,NE India:Some preliminary results[J].Quaternary Geochronology,2(1-4):278—283.
Vassallo R,Ritz J F,Braucher R,et al.2005.Dating faulted alluvial fans with cosmogenic10Be in the Gurvan Bogdmountain range(Gobi-Altay,Mongolia):Climatic and tectonic implications[J].Terra Nova,17(3):278—285.
Wang Hu,Ran Yong-kang,Li Yan-bao,et al.2013.Holocene palaeoseismologic record of earthquakes on theZemuhe Fault on the southeastern margin of the Tibetan plateau[J].Geophysical Journal International,193(1):11—28.
Wintle A G,Huntley D J.1982.Thermoluminescence dating of sediments[J].Quaternary Science Reviews,1(1):31—53.
Yang Hui-li,Chen Jie,Thompson J A,et al.2012.Optical dating of the 12 May 2008,MS8.0 Wenchuan earthquakerelated sediments:Tests of zeroing assumptions[J].Quaternary Geochronology,10:273—279.
Yin Jin-hui,Timothy Jull A J,Burr G S,et al.2012.A wiggle-match age for the millennium eruption of Tianchivolcano at Changbaishan,northeastern China[J].Quaternary Science Reviews,47:150—159.
李安,冉勇康,徐良鑫,等.2011.西南天山东柯坪推覆系古地震初步研究[J].地震地质,33(4):752—764.doi:10.3969/j.issn.0253-4967.2011.04.002.LI An,RAN Yong-kang,XU Liang-xin,et al.2011.A preliminary study on paleoearthquakes in the eastern Kalpinnappe system,southwestern Tianshan,China[J].Seismology and Geology,33(4):752—764(in Chinese).
毛凤英,张培震.1995.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].见:活动断裂研究(4).北京:地震出版社.153—164.MAO Feng-ying,ZHANG Pei-zhen.1995.Progressive constraining method in paleoseismic study and paleoearthquakesalong the major active faults in northern Xinjiang[A].In:Institute of Geology,SSB(ed).Research of ActiveFault(4).Seismological Press,Beijing.153—164(in Chinese).
冉勇康,王虎,李彦宝,等.2012a.中国大陆古地震研究的关键技术与案例解析(1):走滑活动断裂的探槽地点、布设与事件识别标志[J].地震地质,34(2):197—210.doi:10.3969/j.issn.0253-4967.2012.02.001.RAN Yong-kang,WANG Hu,LI Yan-bao,et al.2012a.Key techniques and several cases analysis in paleoseismicstudies in mainland China(1):Trenching sites,layouts and paleoseismic indicators on active strike-slip faults[J].Seismology and Geology,34(2):197—210(in Chinese).
冉勇康,陈立春,陈文山,等.2012b.中国大陆古地震研究的关键技术与案例解析(2):汶川地震地表变形特征与褶皱逆断层古地震识别[J].地震地质,34(3):385—400.doi:10.3969/j.issn.0253-4967.2012.03.001.RAN Yong-kang,CHEN Li-chun,CHEN Wen-shan,et al.2012b.Key techniques and several cases analysis inpaleoseismic studies in mainland China(2):Surface deformation characteristics of Wenchuan earthquake andpaleoseismic indicators on fold-reverse fault[J].Seismology and Geology,34(3):385—400(in Chinese).
冉勇康,李彦宝,杜鹏,等.2014.中国大陆古地震研究的关键技术与案例解析(3):正断层破裂特征、环境影响与古地震识别[J].地震地质,36(2):287—301.doi:10.3969/j.issn.0253-4967.2014.02.001.RAN Yong-kang,LI Yan-bao,DU Peng,et al.2014.Key techniques and several cases analysis in paleoseismicstudies in mainland China(3):Rupture characteristics,environment impact and paleoseismic indicators on normalfaults[J].Seismology and Geology,36(2):287—301(in Chinese).
冉勇康,王虎,张培震,等.2013.古地震研究的技术和方法[A].见:丁仲礼主编.固体地球科学研究方法.北京:科学出版社.258—275.RAN Yong-kang,WANG Hu,ZHANG Pei-zhen,et al.2013.Techniques and Methods of Paleoseismic Studies[A].In:DING Zhong-li(ed).Methods of Research in Solid Earth Sciences.Science Press,Beijing.258—275(inChinese).
王虎,冉勇康,李彦宝,等.2013.则木河断裂上古地震破裂与小型三角状拉分盆地演化[J].中国科学(D辑),43(7):1106—1114.WANG Hu,RAN Yong-kang,LI Yan-bao,et al.2013.Paleoseismic ruptures and evolution of a small triangular pullapart basin on the Zemuhe Fault[J].Science in China(Ser D),56(3):504—512.
徐良鑫,冉勇康,刘华国,等.2011.柯坪塔格山前层状地貌面与晚第四纪逆断层变形:以三岔口北西山前断错地貌为例[J].地震地质,33(4):777—788.doi:10.3969/j.issn.0253-4967.2011.04.004.XU Liang-xin,RAN Yong-kang,LIU Hua-guo,et al.2011.Deformation of reverse fault and layered landform inpiedmont of Kalpintag Mountains during the late Quaternary:Example from the faulted landform of northwesternSanchakou[J].Seismology and Geology,33(4):777—788(in Chinese).
杨会丽.2013.地震相关快速沉积物释光测年研究[D]:[学位论文].北京:中国地震局地质研究所.YANG Hui-li.2013.Optical dating research of rapidly deposited sediments related to earthquakes[D].Dissertation.Institute of Geology,China Earthquake Administration,Beijing(in Chinese).
Anderson R S,Repka J L,Dick G S.1996.Explicit treatment of inheritance in dating depositional surfaces using insitu10Be and26Al[J].Geology,24(1):47—51.
Bailey R M,Singarayer J S,Ward S,et al.2003.Identification of partial resetting using De as a function ofillumination time[J].Radiation Measurements,37(4-5):511—518.
Biasi G,Weldon II R J,Scharer K.2011.Rupture length and paleomagnitude estimates from point measurements ofdisplacement—A model-based approach[J].Geological Society of America Special Papers,479:195—204.
Bierman P R,Alan R G,Marc W C.1995.Cosmogenic ages for earthquake recurrence intervals and debris flow fandeposition,Owens Valley,California[J].Science,270(5235):447—450.
Brown E T,Bourlés D L,Raisbeck G M,et al.1998.Estimation of slip rates in the southern Tien Shan using cosmicray exposure dates of abandoned alluvial fans[J].Bulletin of the Geological Society of America,110(3):377—386.
Chen Li-chun,Ran Yong-kang,Wang Hu,et al.2013.Paleoseismology and kinematic characteristics of theXiaoyudong rupture,a short but significant strange segment characterized by the May 12,2008,MW7.9earthquake in Sichuan,China[J].Tectonophysics,584:91—101.
Cunha P P,Buylaert J P,Murray A S,et al.2010.Optical dating of clastic deposits generated by an extreme marinecoastal flood:The 1755 tsunami deposits in the Algarve(Portugal)[J].Quaternary Geochronology,5(2-3):329—335.
Duller G A T.2008.Single-grain optical dating of Quaternary sediments:Why aliquot size matters in luminescencedating[J].Boreas,37(4):589—612.
Galimberti M,Ramsey C B.2004.Wiggle-match dating of tree-ring sequences[J].Radiocarbon,46(2):917—924.
Godfrey-Smith D I,Huntley D J,Chen W H.1988.Optical dating studies of quartz and feldspar sediment extracts[J].Quaternary Science Reviews,7(3-4):373—380.
Hidy A J,Gosse J C,Pederson J L,et al.2010.A geologically constrained Monte Carlo approach to modelingexposure ages from profiles of cosmogenic nuclides:An example from Lees Ferry,Arizona[J].Geochemistry,Geophysics,Geosystems,11(9):Q0AA10.doi:10.1029/2010GC003084.
Lal D.1991.Cosmic ray labeling of erosion surfaces:In situ nuclide production rates and erosion models[J].Earthand Planetary Science Letters,104:424—439.
Li An,Ran Yong-kang,Xu Liangh-xin,et al.2013.Paleoseismic study of the east Kalpintage Fault in southwestTianshan based on deformation of alluvial fans and10Be dating[J].Natural Hazards,68(2):1075—1087.
Lu Yan-chou,Prescott J R,Zhao Hua,et al.2002.Optical dating of colluvial deposits from Xiyangfang,China andthe relation to palea-earthquake events[J].Quaternary Science Reviews,21(8-9):1087—1097.
Madsen A T,Murray A S,Andersen T J,et al.2007.Optical dating of young tidal sediments in the Danish WaddenSea[J].Quaternary Geochronology,2(1-4):89—94.
Mc Calpin J P.2009.Paleoseismology[M].Academic Press.
Nishiizumi K,Kohl C P,Arnold J R,et al.1993.Role of in situ cosmogenic nuclides10Be and26Al in the study ofdiverse geomorphic processes[J].Earth Surface Processes and Landforms,18:407—425.
Ran Yong-kang,Chen Li-chun,Chen Jie,et al.2010.Paleoseismic evidence and repeat time of large earthquakes atthree sites along the Longmenshan fault zone[J].Tectonophysics,491(1-4):141—153.
Ran Yong-kang,Chen Wen-shan,Xu Xi-wei,et al.2013.Paleoseismic events and recurrence interval along theBeichuan-Yingxiu Fault of Longmenshan Fault zone,Yingxiu,Sichuan,China[J].Tectonophysics,584:81—90.
Repka J L,Anderson R S,Finkel R C.1997.Cosmogenic dating of fluvial terraces,Fremont River,Utah[J].Earthand Planetary Science Letters,152(1-4):59—73.
Santos G M,Alexandre A,Coe H H G,et al.2010.The phytolith14C puzzle:A tale of background determinationsand accuracy tests[J].Radiocarbon,52(1):113—128.
Singarayer J S,Bailey R M,Ward S,et al.2005.Assessing the completeness of optical resetting of quartz OSL in thenatural environment[J].Radiation Measurements,40(1):13—25.
Stokes S,Bray H E,Blum M D.2001.Optical resetting in large drainage basins:Tests of zeroing assumptions usingsingle-aliquot procedures[J].Quaternary Science Reviews,20(5-9):879—885.
Talma A S,Vogel J C.1993.A simplified approach to calibrating14C dates[J].Radiocarbon,35(2):317—322.
Thomas P J,Reddy D V,Kumar D,et al.2007.Optical dating of liquefaction features to constrain prehistoricearthquakes in Upper Assam,NE India:Some preliminary results[J].Quaternary Geochronology,2(1-4):278—283.
Vassallo R,Ritz J F,Braucher R,et al.2005.Dating faulted alluvial fans with cosmogenic10Be in the Gurvan Bogdmountain range(Gobi-Altay,Mongolia):Climatic and tectonic implications[J].Terra Nova,17(3):278—285.
Wang Hu,Ran Yong-kang,Li Yan-bao,et al.2013.Holocene palaeoseismologic record of earthquakes on theZemuhe Fault on the southeastern margin of the Tibetan plateau[J].Geophysical Journal International,193(1):11—28.
Wintle A G,Huntley D J.1982.Thermoluminescence dating of sediments[J].Quaternary Science Reviews,1(1):31—53.
Yang Hui-li,Chen Jie,Thompson J A,et al.2012.Optical dating of the 12 May 2008,MS8.0 Wenchuan earthquakerelated sediments:Tests of zeroing assumptions[J].Quaternary Geochronology,10:273—279.
Yin Jin-hui,Timothy Jull A J,Burr G S,et al.2012.A wiggle-match age for the millennium eruption of Tianchivolcano at Changbaishan,northeastern China[J].Quaternary Science Reviews,47:150—159.
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