依兰-伊通断裂全新世活动的新发现及其意义
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摘要
郯庐断裂带东北段依兰-伊通断裂历史上没有发生过6级以上地震,一般认为是第四纪早期活动断裂,为中强地震发震构造。通过高分辨率卫星影像解译和野外调查,在该断裂多个段落发现断错河流Ⅰ级阶地等全新世地貌面、高1～2m的地表陡坎。其中,在通河县附近的最新地表陡坎长约70km,舒兰附近的最新地表陡坎长约10km。分别对黑龙江通河县和吉林舒兰县的陡坎进行了探槽开挖,发现通河段断层断错至近地表,被断错的最新地层年龄为距今(1730±40)a,舒兰段断层断错晚更新世地层,被距今(2360±40)a的黑色炭质黏土覆盖。这些资料表明依兰-伊通断裂至少部分段落为全新世以来的活动断裂,并且发生过7级以上强震。因此,有必要对依兰-伊通断裂晚第四纪以来的活动特征开展详细研究,以查明该断裂的空间分布、最新活动时代、分段特征、大震重复间隔等,为评价未来地震危险性及地震区划等提供依据,对东北地区的防震减灾具有重要意义。
No earthquake greater than M6 has been documented on the Yilan-Yitong Fault,and no trace of activity since the late pleistocene has been seen either at the northeastern section of the famed Tanlu grand fault zone in eastern China.Thus this fault is recognized active in the early Quaternary and capable of generating moderate quakes.By analyzing high-resolution satellite images and field work,a 70km-long geomorphic scarp in Tonghe County of Heilongjiang Province and a 10km-long geomorphic scarp in Shulan County of Jilin Province were discovered.The scarps are 1～2m high and offset the young terraces.Subsequently,the trench at Tonghe County revealed fault displacement which almost reaches the surface.The uppermost stratum dislocated by the fault is dated to be 1730±40 years B.P.Analysis of geomorphic feature of the fault scarp and the trench profile suggests that an M≥7 paleoearthquake occurred along the fault since 1730±40 B.P.The trench at Shulan County reveals the faulted late Pleistocene stratum covered by stratum dated to be 2360±40 years B.P.All these data suggest that some segments of Yilan-Yitong Fault are active since Holocene and M7 earthquake occurred.So,further detailed research will be necessary to determine the range of the latest activity of this fault,the time of the rupture and recurrence intervals of major earthquakes.These data will be of great significance for earthquake zonation and assessment of seismic risk in this region.
No earthquake greater than M6 has been documented on the Yilan-Yitong Fault,and no trace of activity since the late pleistocene has been seen either at the northeastern section of the famed Tanlu grand fault zone in eastern China.Thus this fault is recognized active in the early Quaternary and capable of generating moderate quakes.By analyzing high-resolution satellite images and field work,a 70km-long geomorphic scarp in Tonghe County of Heilongjiang Province and a 10km-long geomorphic scarp in Shulan County of Jilin Province were discovered.The scarps are 1～2m high and offset the young terraces.Subsequently,the trench at Tonghe County revealed fault displacement which almost reaches the surface.The uppermost stratum dislocated by the fault is dated to be 1730±40 years B.P.Analysis of geomorphic feature of the fault scarp and the trench profile suggests that an M≥7 paleoearthquake occurred along the fault since 1730±40 B.P.The trench at Shulan County reveals the faulted late Pleistocene stratum covered by stratum dated to be 2360±40 years B.P.All these data suggest that some segments of Yilan-Yitong Fault are active since Holocene and M7 earthquake occurred.So,further detailed research will be necessary to determine the range of the latest activity of this fault,the time of the rupture and recurrence intervals of major earthquakes.These data will be of great significance for earthquake zonation and assessment of seismic risk in this region.
引文
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郑照福,于恩影.2006.依兰-伊通地堑断裂北段地震活动的某些特征探讨[J].东北地震研究,22(1):27—31.ZHENG Zhao-fu,YU En-ying.2006.Study on some seismicity characteristics of the northen section on Yilan-Yitong gra-ben fault[J].Seismological Research of Northeast China,22(1):27—31(in Chinese).
朱永.1999.依兰地堑盆地地震活动及其背景浅析[J].东北地震研究,15(1):76—78.ZHU Yong.1999.Seismicity background in Yilan graben basin[J].Seismological Research of Northeast China,15(1):76—78(in Chinese).
朱光,刘国生,Dunlap W J,等.2004.郯庐断裂带同造山走滑运动的40Ar/39Ar年代学证据[J].科学通报,49(2):190—198.ZHU Guang,LIU Guo-sheng,Dunlap W J.et al.2004.40Ar/39Ar geochronological constraints on syn-orogenic strike-slipmovement of Tan-Lu Fault zone[J].Chinese Science Bulletin,49(5):499—508.
荆凤,申旭辉,洪顺英,等.2006.基于遥感技术研究依兰-伊通断裂带[J].地震,26(3):79—84.JING Feng,SHEN Xu-hui,HONG Shun-ying,et al.2006.A study on Yilan-Yitong Fault zone based on remote sensingtechnology[J].Earthquake,26(3):79—84(in Chinese).
李西双,刘保华,赵月霞,等.2010.渤海海域晚更新世—全新世的活动构造[J].海洋学报,32(5):52—59.LI Xi-shuang,LIU Bao-hua,ZHAO Yue-xia,et al.2010.Late Pleistocene-Holocene submarine active structures in theBohai Sea[J].Acta Oceanologica Sinica,32(5):52—59(in Chinese).
郑照福,于恩影.2006.依兰-伊通地堑断裂北段地震活动的某些特征探讨[J].东北地震研究,22(1):27—31.ZHENG Zhao-fu,YU En-ying.2006.Study on some seismicity characteristics of the northen section on Yilan-Yitong gra-ben fault[J].Seismological Research of Northeast China,22(1):27—31(in Chinese).
朱永.1999.依兰地堑盆地地震活动及其背景浅析[J].东北地震研究,15(1):76—78.ZHU Yong.1999.Seismicity background in Yilan graben basin[J].Seismological Research of Northeast China,15(1):76—78(in Chinese).
朱光,刘国生,Dunlap W J,等.2004.郯庐断裂带同造山走滑运动的40Ar/39Ar年代学证据[J].科学通报,49(2):190—198.ZHU Guang,LIU Guo-sheng,Dunlap W J.et al.2004.40Ar/39Ar geochronological constraints on syn-orogenic strike-slipmovement of Tan-Lu Fault zone[J].Chinese Science Bulletin,49(5):499—508.
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