福州盆地的地震环境与主要断层潜在地震的最大震级评价
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摘要
综合探查表明 ,福州盆地的主要断层均无全新世活动。通过区域地壳动力学与地震构造背景分析、地震活动水平统计对比等 ,综合判定了福州盆地的地震环境及主要断层潜在地震的最大震级。结果表明 :福州盆地位于台湾动力触角对大陆作用的弱影响区 ,但靠近强、弱影响区的过渡边界 ,处于有、无≥ 6级强震区的过渡地带。与福建—粤东北沿海发生过强震的地段相比 ,福州盆地及附近主要断裂的最晚活动时代偏老 ,壳内的低速层不显著。另外 ,在福建及邻区的 12个地震构造单元中 ,福州盆地单元的地震活动水平最低。该盆地西缘和南缘的闽候 -南屿断层和五虎山北麓断层是具有发生中等地震潜势的相对危险断层段 ,潜在地震的最大震级估值为MS6 .0和 5 .6。
Comprehensive prospecting in Fuzhou basin has revealed that all the main faults in the basin have not been active since Holocene time. Therefore, how to assess the long term seismic risk of such a type of fault has become an important problem. Taking the Fuzhou basin as an example, we seek after a possible way to evaluate the long term seismic risk on non Holocene active faults in eastern China. Firstly this paper demonstrates the position of the Fuzhou basin in the regional earthquake environment by analyzing regional crustal dynamics and seismic background, and then finds out the fault segments of relatively high seismic risk and estimate the maximum magnitude of potential earthquakes on these fault segments through the comparison of seismotectonic conditions and the statistic analysis of seismic activity levels in individual seismotectonic zones. The main results are as follows: The Fuzhou basin lies in the area that has been influenced slightly by the action of the Taiwan Dynamic Wedge (TDW), but is close to the border between the areas that are slightly and strongly influenced by the TDW, and is located at the transition zone between regions with and without strong earthquake (of M S≥6.0) occurrence. As compared with the seismotectonic background in Fujian northeast Guangdong areas, where strong earthquakes have occurred, the main faults in Fuzhou basin and its neighboring area have older ages of the latest activities, while the crust beneath the region contains less distinct low velocity layers. Moreover, among 12 zones that are taken as statistic units for seismicity in Fujian, northeastern Guandong and the border region among Fujian, Guangdong and Jiangxi Provinces, the unit in Fuzhou basin shows the lowest level of seismicity. It is suggested that the Minhou Nanyu Fault along the western border of the Fuzhou basin and the Wuhushan northern foot fault along the southern border of the basin are the two fault segments with relatively high potential of moderate to strong earthquakes. The maximum magnitudes of the potential earthquakes on the two fault segments have been estimated to be M S6.0 and 5.6, respectively, on the basis of the worldwide empirical relationship between subsurface rupture scale and magnitude of earthquake.
Comprehensive prospecting in Fuzhou basin has revealed that all the main faults in the basin have not been active since Holocene time. Therefore, how to assess the long term seismic risk of such a type of fault has become an important problem. Taking the Fuzhou basin as an example, we seek after a possible way to evaluate the long term seismic risk on non Holocene active faults in eastern China. Firstly this paper demonstrates the position of the Fuzhou basin in the regional earthquake environment by analyzing regional crustal dynamics and seismic background, and then finds out the fault segments of relatively high seismic risk and estimate the maximum magnitude of potential earthquakes on these fault segments through the comparison of seismotectonic conditions and the statistic analysis of seismic activity levels in individual seismotectonic zones. The main results are as follows: The Fuzhou basin lies in the area that has been influenced slightly by the action of the Taiwan Dynamic Wedge (TDW), but is close to the border between the areas that are slightly and strongly influenced by the TDW, and is located at the transition zone between regions with and without strong earthquake (of M S≥6.0) occurrence. As compared with the seismotectonic background in Fujian northeast Guangdong areas, where strong earthquakes have occurred, the main faults in Fuzhou basin and its neighboring area have older ages of the latest activities, while the crust beneath the region contains less distinct low velocity layers. Moreover, among 12 zones that are taken as statistic units for seismicity in Fujian, northeastern Guandong and the border region among Fujian, Guangdong and Jiangxi Provinces, the unit in Fuzhou basin shows the lowest level of seismicity. It is suggested that the Minhou Nanyu Fault along the western border of the Fuzhou basin and the Wuhushan northern foot fault along the southern border of the basin are the two fault segments with relatively high potential of moderate to strong earthquakes. The maximum magnitudes of the potential earthquakes on the two fault segments have been estimated to be M S6.0 and 5.6, respectively, on the basis of the worldwide empirical relationship between subsurface rupture scale and magnitude of earthquake.
引文
①中国地震局厦门地震勘测研究中心,2002,福州盆地主要断层条带状地震地质详细调查与综合制图报告。
①最新版的《中国历史强震目录》将1574年地震震中确定在福州—莆田以东海域(25.5°N ,120.0°E),震级为5。本文作者已初步论证该地震可达到6级,并从沿岸破坏区的展布推断属NE向滨海断裂发震(见:闻学泽,徐锡伟,2003,对1067年和1574年东南沿海两次地震事件的分析,中国地震学会历史地震与地震地质专业委员会2003年学术会议论文,将另刊发表)。
①中国地震局厦门地震勘测研究中心,2002,福州盆地主要断层条带状地震地质详细调查与综合制图报告及附图,福建省人民政府和中国地震局“十五”重点项目成果。
陈峰.1982.福建近岸海底地形的初步研究〔J〕.台湾海峡,2(1):42—45.
CHENFeng.1982.Apreliminarystudyonthenear coastalseafloortopographyofFujian〔J〕.TaiwanStrait,2(1):42—45(inChinese).
陈园田.1984.新构造运动与泉州海外8级地震〔J〕.地震,4(1):42—45.
CHENYuan tian.1984.DifferentialneotectonicmovementandQuanzhouoffshoreearthquakeofM 8〔J〕.Earth quake,4(1):42—45(inChinese).
丁祥焕主编.1999.福建东南沿海活动断裂与地震〔M〕.福州:福建科学技术出版社.
DINGXiang huan(ed).1999.ActiveFaultsandEarthquakesintheCoastalRegionofSoutheasternFujian〔M〕.PeoplePublishingHouseofFujian,Fuzhou(inChinese).
国家地震局震害防御司编.1995.中国历史强震目录〔M〕.北京:地震出版社.
DepartmentofEarthquakeDisasterPrevention,StateSeismologicalBureau(ed).1995.CatalogueofHistoricalStrongEarthquakesofChina〔Z〕.SeismologicalPress,Beijing(inChinese).
国家地震局地球物理研究所,复旦大学历史地理研究所编.1990a,b,c.中国历史地震图集(远古至元时期,明时期,清时期)〔M〕.北京:中国地图出版社.1—174,1-194,1-244.
InstituteofGeophysicsofStateSeismologicalBureau,InstituteofHistoricGeographyofFudanUniversity(ed).1990a,b,c.AtlasofHistoricalEarthquakesofChina(RemoteantiquitytoYuanDynasties,MingDynasty,andQingDynastyVolumes)〔M〕.ChinaCartographicPublishingHouse,Beijing.1—174,1—194,and1—244(inChinese).
黄卿团,丁祥焕,庄进耀.1999.福建东南沿海晚第四纪断陷构造的形成与发育〔A〕.见:中国地震局地质研究所编.活动断裂研究(7).北京:地震出版社.67—80.
HUANGQing tuan,DINGXiang huan,ZHUANGJin yiao.1999.FormationandDevelopmentofFault subsidenceTectonicsinLateQuaternaryalongtheCoastalRegionoftheEasternFujianProvince〔A〕.In:InstituteofGe ology,SSB (ed).ResearchonActivefault(7).SeismologicalPress,Beijing.67—80(inChinese).
黄卿团,汪一鹏,宋方敏,等.2001.福建漳州盆地岱山岩-珩坑北西向断裂带第四纪活动特征〔J〕.华南地震,21(2):28—35.
HUANGQing tuan,WANGYi peng,SONGFang min,etal.2001.QuaternaryactivefeatureofthenorthwestfaultzoneatDaishanyanHengkenginZhangzhoubasin,Fujian〔J〕.SouthChinaJournalofSeismology,21(2):28—35(inChinese).
林锦华.1999.长乐-诏安断裂带活动特征与继承性活动〔J〕.华南地震,19(2):57—61.
LINJin hua.1999.TheactivefeatureandinheritingactivityofChangleZhaoanfaultzone〔J〕.SouthChinaJournalofSeismology,19(2):57—61(inChinese).
李延兴,胡新康,帅平,等.2002.强震发生的应变场特征〔J〕.地震研究,25(增刊):57—64.
LIYan xing,HUXin kang,SHUAIPing,etal.2002.Astudyonthefeatureofstrainfieldexposedbeforetheoc currenceofstrongearthquakes〔J〕.JournalofSeismologicalResearch,25(Suppl):57—64(inChinese).
廖其林,王振明,王屏路,等.1988.福州—泉州—汕头地区地壳结构的爆炸地震研究〔J〕.地球物理学报,31(3):270—280.
LIAOQi lin,WANGZhen ming,WANGPin lu,etal.1988.ExplosionseismicstudyofthecrustalstructureinFuzhouQuanzhouShantouregion〔J〕.ActaGeophysicaSinica,31(3):270—280(inChinese).
廖其林,王振明,邱陶兴,等.1990.福州盆地及其周围地区地壳深部结构与构造的初步研究〔J〕.地球物理学报,33(2):163—173.
LIAOQi lin,WANGZhen ming,QIUTao xing,etal.1990.PreliminaryresearchofthecrustalstructureinFuzhoubasinanditsadjacentarea〔J〕.ActaGeophysicaSinica,33(2):163—173(inChinese).
马宗晋,王乾盈,徐杰,等.2002.台湾海峡两岸横向构造的对比研究〔J〕.中国科学(D辑),32(6):441—451.
MAZongjin,WANGQianYing,XUJie,etal.2002.StudyonthetransversestructuresacrossTaiwanStrait〔J〕.ScienceinChina(SeriesD),45(12):1114—1126.
闵伟,朱金芳,冉勇康,等.2002.福州盆地活动断裂的探槽研究〔J〕.地震地质,24(4):514—523.
MINWei,ZHUJin fang,RANYong kang,etal.2002.StudyontheactivefaultsinFuzhoubasinthroughtrench ing〔J〕.SeismologyandGeology,24(4):514—523(inChinese).
魏柏林主编.2001.东南沿海地震活动特征?
①最新版的《中国历史强震目录》将1574年地震震中确定在福州—莆田以东海域(25.5°N ,120.0°E),震级为5。本文作者已初步论证该地震可达到6级,并从沿岸破坏区的展布推断属NE向滨海断裂发震(见:闻学泽,徐锡伟,2003,对1067年和1574年东南沿海两次地震事件的分析,中国地震学会历史地震与地震地质专业委员会2003年学术会议论文,将另刊发表)。
①中国地震局厦门地震勘测研究中心,2002,福州盆地主要断层条带状地震地质详细调查与综合制图报告及附图,福建省人民政府和中国地震局“十五”重点项目成果。
陈峰.1982.福建近岸海底地形的初步研究〔J〕.台湾海峡,2(1):42—45.
CHENFeng.1982.Apreliminarystudyonthenear coastalseafloortopographyofFujian〔J〕.TaiwanStrait,2(1):42—45(inChinese).
陈园田.1984.新构造运动与泉州海外8级地震〔J〕.地震,4(1):42—45.
CHENYuan tian.1984.DifferentialneotectonicmovementandQuanzhouoffshoreearthquakeofM 8〔J〕.Earth quake,4(1):42—45(inChinese).
丁祥焕主编.1999.福建东南沿海活动断裂与地震〔M〕.福州:福建科学技术出版社.
DINGXiang huan(ed).1999.ActiveFaultsandEarthquakesintheCoastalRegionofSoutheasternFujian〔M〕.PeoplePublishingHouseofFujian,Fuzhou(inChinese).
国家地震局震害防御司编.1995.中国历史强震目录〔M〕.北京:地震出版社.
DepartmentofEarthquakeDisasterPrevention,StateSeismologicalBureau(ed).1995.CatalogueofHistoricalStrongEarthquakesofChina〔Z〕.SeismologicalPress,Beijing(inChinese).
国家地震局地球物理研究所,复旦大学历史地理研究所编.1990a,b,c.中国历史地震图集(远古至元时期,明时期,清时期)〔M〕.北京:中国地图出版社.1—174,1-194,1-244.
InstituteofGeophysicsofStateSeismologicalBureau,InstituteofHistoricGeographyofFudanUniversity(ed).1990a,b,c.AtlasofHistoricalEarthquakesofChina(RemoteantiquitytoYuanDynasties,MingDynasty,andQingDynastyVolumes)〔M〕.ChinaCartographicPublishingHouse,Beijing.1—174,1—194,and1—244(inChinese).
黄卿团,丁祥焕,庄进耀.1999.福建东南沿海晚第四纪断陷构造的形成与发育〔A〕.见:中国地震局地质研究所编.活动断裂研究(7).北京:地震出版社.67—80.
HUANGQing tuan,DINGXiang huan,ZHUANGJin yiao.1999.FormationandDevelopmentofFault subsidenceTectonicsinLateQuaternaryalongtheCoastalRegionoftheEasternFujianProvince〔A〕.In:InstituteofGe ology,SSB (ed).ResearchonActivefault(7).SeismologicalPress,Beijing.67—80(inChinese).
黄卿团,汪一鹏,宋方敏,等.2001.福建漳州盆地岱山岩-珩坑北西向断裂带第四纪活动特征〔J〕.华南地震,21(2):28—35.
HUANGQing tuan,WANGYi peng,SONGFang min,etal.2001.QuaternaryactivefeatureofthenorthwestfaultzoneatDaishanyanHengkenginZhangzhoubasin,Fujian〔J〕.SouthChinaJournalofSeismology,21(2):28—35(inChinese).
林锦华.1999.长乐-诏安断裂带活动特征与继承性活动〔J〕.华南地震,19(2):57—61.
LINJin hua.1999.TheactivefeatureandinheritingactivityofChangleZhaoanfaultzone〔J〕.SouthChinaJournalofSeismology,19(2):57—61(inChinese).
李延兴,胡新康,帅平,等.2002.强震发生的应变场特征〔J〕.地震研究,25(增刊):57—64.
LIYan xing,HUXin kang,SHUAIPing,etal.2002.Astudyonthefeatureofstrainfieldexposedbeforetheoc currenceofstrongearthquakes〔J〕.JournalofSeismologicalResearch,25(Suppl):57—64(inChinese).
廖其林,王振明,王屏路,等.1988.福州—泉州—汕头地区地壳结构的爆炸地震研究〔J〕.地球物理学报,31(3):270—280.
LIAOQi lin,WANGZhen ming,WANGPin lu,etal.1988.ExplosionseismicstudyofthecrustalstructureinFuzhouQuanzhouShantouregion〔J〕.ActaGeophysicaSinica,31(3):270—280(inChinese).
廖其林,王振明,邱陶兴,等.1990.福州盆地及其周围地区地壳深部结构与构造的初步研究〔J〕.地球物理学报,33(2):163—173.
LIAOQi lin,WANGZhen ming,QIUTao xing,etal.1990.PreliminaryresearchofthecrustalstructureinFuzhoubasinanditsadjacentarea〔J〕.ActaGeophysicaSinica,33(2):163—173(inChinese).
马宗晋,王乾盈,徐杰,等.2002.台湾海峡两岸横向构造的对比研究〔J〕.中国科学(D辑),32(6):441—451.
MAZongjin,WANGQianYing,XUJie,etal.2002.StudyonthetransversestructuresacrossTaiwanStrait〔J〕.ScienceinChina(SeriesD),45(12):1114—1126.
闵伟,朱金芳,冉勇康,等.2002.福州盆地活动断裂的探槽研究〔J〕.地震地质,24(4):514—523.
MINWei,ZHUJin fang,RANYong kang,etal.2002.StudyontheactivefaultsinFuzhoubasinthroughtrench ing〔J〕.SeismologyandGeology,24(4):514—523(inChinese).
魏柏林主编.2001.东南沿海地震活动特征?
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