甘宁青地区现今构造形变异常与地震
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摘要
通过对甘宁青地区大地垂直形变、断层形变和GPS水平形变测量资料的处理分析 ,结合地质构造和有形变资料积累以来本区域多次中、强地震活动 ,对本区现今构造形变异常与中强以上地震蕴育的一些特征进行了初步研究和探讨。结果表明 :①甘宁青监测区主要断裂附近构造形变相对强烈 ;垂直差异运动强度和变形态势随时间演变 ,水平运动与变形呈明显的挤压走滑特征。②本区构造形变与地震蕴育的主控应力来自青藏块体持续NE向挤压运动 ;构造形变和地震活动的时空分布演化与块体活动及区域构造应力场动态演化密切相关。③区域构造块体边界地带出现的异常隆起与高梯度形变带及显著的断层形变异常 ,是蕴育中、强震的标志 ,但地震并不一定发生在幅度最大的部位 ,而往往发生在断层形变异常呈现“趋势积累 -加速 -转折”变化特征的地段及附近。在此基础上 ,对研究区强震危险性进行了初步预测。
Through processing and analyzing the observational data of geodetic vertical deformation, fault deformation and horizontal deformation by GPS in Gansu Ningxia Qinghai area and combining them with the set of geological structure and many medium strong seismic activities in this area some features of recent tectonic deformation anomaly and the development of medium strong earthquakes are studied preliminarily. The results show as follows.①Near to the main faults in Gansu Ningxia Qinghai monitoring area tectonic deformation are relatively larger.The vertical movement strength and deformation status evolve with time.The horizontal movement and deformation show obvious compressional strike slip character. ②The dominant stress of tectonic deformation and seismic development in this area comes from the persistent northeastward compression of Qinghai Tibet block;The time spatial distribution evolution of tectonic deformation and seismic activities are closely related to dynamic evolution of block motion and regional tectonic stress field. ③The abnormal uplift and high gradient deformation belts and remarkable fault deformation anomaly on the borders of regional tectonic blocks are indicators of developing medium strong earthquake but the earthquake does not certainly take place in the position with maxium deformation, it usually occur in the region where fault deformation anomaly shows "trend accumulation acceleration turn" variation character or nearby. On the basis of above study, a preliminary prediction for strong earthquake risk in this area is given.
Through processing and analyzing the observational data of geodetic vertical deformation, fault deformation and horizontal deformation by GPS in Gansu Ningxia Qinghai area and combining them with the set of geological structure and many medium strong seismic activities in this area some features of recent tectonic deformation anomaly and the development of medium strong earthquakes are studied preliminarily. The results show as follows.①Near to the main faults in Gansu Ningxia Qinghai monitoring area tectonic deformation are relatively larger.The vertical movement strength and deformation status evolve with time.The horizontal movement and deformation show obvious compressional strike slip character. ②The dominant stress of tectonic deformation and seismic development in this area comes from the persistent northeastward compression of Qinghai Tibet block;The time spatial distribution evolution of tectonic deformation and seismic activities are closely related to dynamic evolution of block motion and regional tectonic stress field. ③The abnormal uplift and high gradient deformation belts and remarkable fault deformation anomaly on the borders of regional tectonic blocks are indicators of developing medium strong earthquake but the earthquake does not certainly take place in the position with maxium deformation, it usually occur in the region where fault deformation anomaly shows "trend accumulation acceleration turn" variation character or nearby. On the basis of above study, a preliminary prediction for strong earthquake risk in this area is given.
引文
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2 WangShuangxu,JiangZaisenandTangChuanfen.Charac teristicsoftheevolutionofrecentverticaldeformationfieldandthecrustalmovementinLanzhouTianshuiWuduarea[J].CrustalDeformationandEarthquake,1995,15(1):62-70.(inChinese)
3 ZhangXiaoliang,JiangZaisen,ChenBing,etal.Prelimi naryresearchonpresentblockdemarcation,movementanddeformationinnortheastmarginofQinghaiTibet[J].JournalofGeodesyandGeodynamics,2002,22(1):61-67.(inChinese)
4 JiangZaisen,ZhangXi,CuiDuxin,etal.Recenthorizon talmovementanddeformationinthenortheastmarginofQinghaiTibet[J].ChineseJournalofGeophysics,2001,44(5):656-644.(inChinese)
5 JiangZaisen,MaZongjin,ZhangXi,etal.Analysisofre centhorizontalcrustalstrainfieldandtectonicdeformationinthenortheastmarginofQinghaiTibetblock[J].Seis mologyandGeology,2001,23(3):337-345.(inChi nese)
6 WangShuangxu,JiangZaisen,ZhangXi,etal.CurrenttectonicdeformationandseismogeniccharacteristicsalongthenortheastmarginofQinghaiXizangblock[J].ActaSeismologicaSinica,2002,24(1):27-34.(inChinese)
7 GongShouwen.EvolutioncharacteristicsofcrustalverticaldeformationinconjoiningzonesofmassesandmassivemovementinShanGanNingQingarea[J].ChineseJour nalofGeophysics,1995,38(3):329-338.(inChinese)
8 JiangZaisen,CuiDuxinandWangShuangxu.Informationseparationforverticalcrustaldeformationfieldanddetermi nationofstrongearthquakeriskarea[A].In:ChenYuntai(ed in chief).Collectedabstractsof6thacademicmeetingofChineseSeismologicalSociety[C].Beijing:SeismologicalPress,1996,171.(inChinese)
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