四川大凉山断裂带古地震研究初步结果
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摘要
沿四川大凉山断裂带的 4条次级断裂开挖了 4个探槽 ,共揭露出 9次古地震事件。根据探槽中年龄样品的测试结果 ,分析了各次事件的距今年龄及其重复间隔。其中 ,有 3个探槽共揭露出4次全新世以来的古地震事件。 9次古地震的垂直位移量在 0 5～ 1 5m之间 ,与鲜水河 -小江断裂带历史地震所产生的垂直位移量进行对比 ,估计它们的震级都在 7级以上
Four prospecting trenches were excavated along 4 subsidiary faults of the Daliangshan fault zone, and 9 paleo-seismic events were revealed by these trenches. West of Doukanzi village, the Tc-1 trench is located on the northern segment of the Shimian-Haitang-Yuexi subsidiary fault. The occurrence time of 2 paleo-earthquakes revealed by this trench is 35ka and 3.5ka, respectively. In the north of Keqilada village, the Tc-2 trench is located on the middle-northern segment of the Puxiong-Zhuhe subsidiary fault. The occurrence time of 2 paleo-seismic events revealed by this trench is 28～30ka and 24ka, respectively. The trench Tc-3 in the south of Tuodu village is located on the middle-northern segment of the Tuodu-Butuo subsidiary fault. The occurrence time of 3 paleo-earthquakes revealed by this trench is 25ka, 10ka and 7.5ka, respectively. The trench TC-4 at Cizijiao village is located on the northern segment of the Jifulada-Jiaojihe subsidiary fault, and the occurrence time of 2 paleo-seismic events revealed by this trench is 15ka and 4.5ka. Among the 9 events, 4 events occurred in Holocene time. The occurrence of the 9 events indicates that the Daliangshan fault zone has been active since late Pleistocene. The vertical displacements produced by these 9 earthquakes are 0.5～1.5m. In comparison to the displacement produced by the historical earthquakes along the Xianshuihe-Xiaojiang fault zone, it can be postulated that the maximum magnitude of these 9 events is M≥7. The study of fault segmentation has shown that a major fault zone can be divided into several segments with independent rupturing history. The segments are separated from each other by relatively large scale bending, turning, crossing and step-over, which may effectively inhibit the propagation of the rupture. The four subsidiary faults of the Daliangshan fault zone are 60～90km in length, and the width of the step-over zone between two subsidiary faults is 5～15km, which is wide enough to inhibit the propagation of rupture on the adjacent faults. That is why the subsidiary faults become an independent rupturing unit. It is concluded, therefore, that the paleo-seismic events revealed by the 4 trenches were independent rupturing events.
Four prospecting trenches were excavated along 4 subsidiary faults of the Daliangshan fault zone, and 9 paleo-seismic events were revealed by these trenches. West of Doukanzi village, the Tc-1 trench is located on the northern segment of the Shimian-Haitang-Yuexi subsidiary fault. The occurrence time of 2 paleo-earthquakes revealed by this trench is 35ka and 3.5ka, respectively. In the north of Keqilada village, the Tc-2 trench is located on the middle-northern segment of the Puxiong-Zhuhe subsidiary fault. The occurrence time of 2 paleo-seismic events revealed by this trench is 28～30ka and 24ka, respectively. The trench Tc-3 in the south of Tuodu village is located on the middle-northern segment of the Tuodu-Butuo subsidiary fault. The occurrence time of 3 paleo-earthquakes revealed by this trench is 25ka, 10ka and 7.5ka, respectively. The trench TC-4 at Cizijiao village is located on the northern segment of the Jifulada-Jiaojihe subsidiary fault, and the occurrence time of 2 paleo-seismic events revealed by this trench is 15ka and 4.5ka. Among the 9 events, 4 events occurred in Holocene time. The occurrence of the 9 events indicates that the Daliangshan fault zone has been active since late Pleistocene. The vertical displacements produced by these 9 earthquakes are 0.5～1.5m. In comparison to the displacement produced by the historical earthquakes along the Xianshuihe-Xiaojiang fault zone, it can be postulated that the maximum magnitude of these 9 events is M≥7. The study of fault segmentation has shown that a major fault zone can be divided into several segments with independent rupturing history. The segments are separated from each other by relatively large scale bending, turning, crossing and step-over, which may effectively inhibit the propagation of the rupture. The four subsidiary faults of the Daliangshan fault zone are 60～90km in length, and the width of the step-over zone between two subsidiary faults is 5～15km, which is wide enough to inhibit the propagation of rupture on the adjacent faults. That is why the subsidiary faults become an independent rupturing unit. It is concluded, therefore, that the paleo-seismic events revealed by the 4 trenches were independent rupturing events.
引文
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DINGGuo yu,TIANQin jian,KONGFan chen,etal.1993.SegmentationofActiveFault:Principle,MethodandApplication〔M〕.Beijing:SeismologicalPress(inChinese)
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,1～2:24～48.
DUPing shan.2000.Strike slipdisplacementandslipratealongtheZemuhefaultzone〔J〕.EarthquakeResearchinSichuan,1/2:24～48(inChinese).
李天,杜其方,游泽李,等.1997.鲜水河断裂带及强震危险性评估〔M〕.成都:成都地图出版社
LITian shao,DUQi fang,YOUZe li,etal.1997.XianshuiheFaultZoneanditsSeismicRiskEvaluation〔M〕.Chengdu:CartographicPublishingHouseofChengdu(inChinese).
李主编.1993.鲜水河小江断裂带〔M〕.北京:地震出版社.
LIPing,ed.1993.TheXianshuiheXiaojiangFaultZone〔M〕.Beijing:SeismologicalPress(inChinese).
裴锡瑜,王新民,张成贵.1998.晚第四纪安宁河断裂分段的基本特征〔J〕.四川地震,4:52～61
PEIXi yu,WANGXin min,ZHANGCheng gui.1998.BasiccharacteristicsofthelateQuaternarysegmentationoftheAnninghefaultzone〔J〕.EarthquakeResearchinSichuan,4:52～61(inChinese).
冉勇康,段瑞涛,邓起东,等.1997.海原断裂高湾子地点三维探槽的开挖与古地震研究〔J〕.地震地质,19(2):97～107.
RANYong kang,DUANRui tao,DENGQi dong,etal.1997.3Dtrenchexcavationand paleoseismologyatGaowanzioftheHaiyuanfault〔J〕.SeismologyandGeology,19(2):97～107(inChinese).
宋方敏,汪一鹏,俞维贤,等.1998.小江活动断裂带〔M〕.北京:地震出版社
SONGFang min,WANGYi peng,YUWei xian,etal.1998.TheActiveXiaojiangFaultZone〔M〕.Beijing:Seis mologicalPress(inChinese).
宋方敏,汪一鹏,俞维贤,等.1996.1713年寻甸地震地表破裂带的识别与论证〔A〕.见:国家地震局地质研究所编.活动断裂研究(5).北京:地震出版社.95～104.
SONGFang min,WANGYi peng,YUWei xian,etal.1996.Recognitionanddemonstrationofthesurfacerupturezoneproducedby1713Xundianearthquake〔A〕.In:InstituteofGeology,SSB ,ed.ResearchonActiveFault(5).Beijing:SeismologicalPress(inChinese).
申旭辉,陈正位,许任德,等.2000.凉山活动构造带晚新生代变形特征与位移规模〔J〕.地震地质,22(3):232～238.
SHENXu hui,CHENZheng wei,XURen de,etal.2000.DeformationcharacteristicsanddisplacementamountoftheLiangshanactivefaultzoneinlateCenozoicera〔J〕.SeismologyandGeology,22(3):232～238(inChi nese)
唐荣昌,韩渭宾主编.1993.四川活动断裂与地震〔M〕.北京:地震出版社
TANGRong chang,HANWei bin,eds.1993.ActiveFaultsandEarthquakesinSichuanProvince〔M〕.Beijing:SeismologicalPress(inChinese).
闻学泽.1995.活动断裂地震潜势的定量评估〔M〕.北京:地震出版社
WENXue ze.1995.QuantitativeEvaluationofEarthquakePotentialofActiveFault〔M〕.Beijing:SeismologicalPress(inChinese).
国家地震局西南烈度队.1977.西南地区地震地质及烈度区划探讨〔M〕.北京:地震出版社
SouthwestChinaSeismicZoningResearchTeam,SSB .1977.SeismogeologyandSeismicZoninginSouthwestChina〔M〕.Beijing:SeismologicalPress(inChinese).
国家地震局西南烈度队.1979.川滇强震区地震地质汇编〔M〕.北京:地震出版社
SouthwestChinaSeismicZoningResearchTeam,SSB .1979.CollectionWorksonSeismogeologyofSichuanandYunnanStrongEarthquakeAreas〔M〕.Beijing:seismologicalPress(inChinese)
中国地震简目汇编组.1988.中国地震简目〔Z〕.北京:科学出版社
CompilationGroupofEarthquakeCatalogueofChina.1988.EarthquakeCatalogueofChina〔Z〕.Beijing:SciencePress(inChinese).
HeimA .1934.EarthquakeregionofTaofu〔J〕.GeolSocAmerBull,45(6):1035～1050.
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