北京房山世界地质公园中元古界雾迷山组地震-海啸序列及地质特征——以野三坡园区为例
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摘要
野三坡园区中元古界(1800～1200Ma B.P)位于燕辽裂陷槽南部中轴断层南支(古紫荆关断裂)之东盘。野三坡雾迷山组笫二段白云岩中的地震序列自下而上分为:A.阶梯状断层与震碎角砾岩变形单元;B.微褶皱-微断层变形单元;C.液化均一变形单元;D.液化卷曲变形单元。这4个变形单元分别代表海底之下深度不足10m内已固结成岩—半固结—弱固结沉积层的变形特征,都经历了前震及主震期(P波和S波)不同程度的影响。海啸系列(海啸岩)自下而上为:E.津浪丘状层单元;F.丘-槽构造层单元和G.粒序均一层单元。海啸是在主震期数十秒后发生的。海底瞬时大幅度抬升,然后突然大幅度下降,使外海海水涌入,引发海啸,形成丘状层及有关变形。余震阶段的震荡流与一次沉降事件分别形成F和G单元。本区中轴断层(古紫荆关断层)是一条海底直立的断层带,对雾迷山组二段中的地震-海啸及沉积过程均起到激发与控制作用。此次震中位于中轴断层带西缘的白石山,震级为7.0～7.5里氏级,是震源浅、裂度大的海底地震。
Yesanpo scenic district was distributed in the eastside of the south branch of the central axial fault in the south Yanshan-Liaoning aulacogen during Mesoproterozoic(1800～1200 Ma B.P.).The seismic sequence(seismites) of the 2nd member of Wumishan Formation in Yesanpo,which is dominantly made up of dolomite,can be subdivided into four units from bottom to top:A.step faults and autoclastic breccia deformation unit;B.microfold-microfault deformation unit;C.liquefied homogenization deformation unit;D.liquefied convolute lamination deformation unit.They represent respectively the deformation features of the consolidated,sub-consoli-dated and weakly consolidated submarine deposits within the depth of 10 meters beneath seafloor.All of these four deformation units had undergone the effect of foreshock and principal phase of earthquake(P-wave and S-wave) in various degrees.The tsunami se-quence(tsunamites) can be subdivided into three units from bottom to top:E.tsunamic hummocky layer;F.groove-mound struc-ture layer;G.homogeneous particle size layer.Tsunami always happens later tens of seconds than principal phase of earthquake and it makes seafloor instantaneous uplift in large amplitude,and then suddenly subsides,which causes the inrush of outer seawater and in-duced the tsunami associated with the formation of hummocky bed.The F and G units are formed by the event of oscillating currents and gravitation deposit respectively in the after shock stage.The central axial fault in the study area(paleo-Zijingguan fault),as a sub-marine vertical fault zone,stimulates and controls the seismic and tsunami as well as the deposit processes in the 2nd member of Wu-mishan Formation.The authors conclude that the epicenter of this submarine earthquake was located at Baishishan in the west border of central axial fault zone with magnitude of the earthquake ranging 7.0～7.5 in Richter scale and shallow seismic source.
Yesanpo scenic district was distributed in the eastside of the south branch of the central axial fault in the south Yanshan-Liaoning aulacogen during Mesoproterozoic(1800～1200 Ma B.P.).The seismic sequence(seismites) of the 2nd member of Wumishan Formation in Yesanpo,which is dominantly made up of dolomite,can be subdivided into four units from bottom to top:A.step faults and autoclastic breccia deformation unit;B.microfold-microfault deformation unit;C.liquefied homogenization deformation unit;D.liquefied convolute lamination deformation unit.They represent respectively the deformation features of the consolidated,sub-consoli-dated and weakly consolidated submarine deposits within the depth of 10 meters beneath seafloor.All of these four deformation units had undergone the effect of foreshock and principal phase of earthquake(P-wave and S-wave) in various degrees.The tsunami se-quence(tsunamites) can be subdivided into three units from bottom to top:E.tsunamic hummocky layer;F.groove-mound struc-ture layer;G.homogeneous particle size layer.Tsunami always happens later tens of seconds than principal phase of earthquake and it makes seafloor instantaneous uplift in large amplitude,and then suddenly subsides,which causes the inrush of outer seawater and in-duced the tsunami associated with the formation of hummocky bed.The F and G units are formed by the event of oscillating currents and gravitation deposit respectively in the after shock stage.The central axial fault in the study area(paleo-Zijingguan fault),as a sub-marine vertical fault zone,stimulates and controls the seismic and tsunami as well as the deposit processes in the 2nd member of Wu-mishan Formation.The authors conclude that the epicenter of this submarine earthquake was located at Baishishan in the west border of central axial fault zone with magnitude of the earthquake ranging 7.0～7.5 in Richter scale and shallow seismic source.
引文
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[13]Seilacher A.Sedimentary structures tentatively attributed to seismic events[J].Marine Geology,1984,55(1/2):1-12.
[14]葛宝勋,刘祖发.含煤岩系中震积岩的首次发现及其特征[J].岩相古地理,1989,43(5):9-13.
[15]吴贤涛,尹国勋.四川峨眉晚侏罗世湖泊沉积中震积岩的发现及其意义[J].沉积学报,1992,10(1):19-24.
[16]Rossetti D F,Goes A M.Deciphering the sedimentological imprint of paleoseismic events:an example from the Aptian Codo Formation,Northern Brazil[J].Sed.Geol.,2000,135(1/4):137-156.
[1]河北省区域地质调查队.1:5万谢家堡幅(J-50-3-B)、大河南幅(J-50-3-C)、镇厂幅(J-50-3-D)、龙门幅(J-50-3-A)区域地质调查联测报告.1981.
[2]Kastens K A,Cita M B.Tsunami-induced sediment transport in the abyssal Mediterranean Sea[J].Geol.Soc.Am.Bull.,1981,92:845-857.
[3]杜远生,韩欣.论海啸作用与海啸岩[J].地质科技情报,2000,19(1):19-22.
[4]杜远生,韩欣.论震积作用和震积岩[J].地球科学进展,2000,15(4):389-394.
[5]杜远生,张传恒,韩欣,等.滇中元古代昆阳群的地震事件沉积及其地质意义[J].中国科学(D辑),2001,31(4):283-289.
[6]杨仕维,李建明.震积岩特征综述及地质意义[J].岩性油气藏,2008,20(1):89-94.
[7]宋天锐.北京十三陵前寒武纪碳酸盐岩地层中的一套可能的地震-海啸序列[J].科学通报,1988,(8):609-611.
[8]乔秀夫,宋天锐,高林志,等.碳酸盐岩振动液化地震序列[J].地质学报,1994,68(1):16-32.
[9]梁定益,宋志敏,赵崇贺,等.河北省白石山中元古代地震遗迹的发现[J].地质通报,2002,21(10):625-630.
[10]乔秀夫,宋天锐,高林志,等.地震中地震记录(古地震)[M].北京:地质出版社,2006.
[11]张传恒,武振杰,高林志,等.华北中元古界雾迷山组地震驱动的软沉积物变形构造及其地质意义[J].中国科学(D辑),2007,37(1):6-8.
[12]乔秀夫,高林志,张传恒.中朝板块中、新元古界年代地层柱与构造环境新思考[J].地质通报,2007,26(5):503-509.
[13]Seilacher A.Sedimentary structures tentatively attributed to seismic events[J].Marine Geology,1984,55(1/2):1-12.
[14]葛宝勋,刘祖发.含煤岩系中震积岩的首次发现及其特征[J].岩相古地理,1989,43(5):9-13.
[15]吴贤涛,尹国勋.四川峨眉晚侏罗世湖泊沉积中震积岩的发现及其意义[J].沉积学报,1992,10(1):19-24.
[16]Rossetti D F,Goes A M.Deciphering the sedimentological imprint of paleoseismic events:an example from the Aptian Codo Formation,Northern Brazil[J].Sed.Geol.,2000,135(1/4):137-156.
[1]河北省区域地质调查队.1:5万谢家堡幅(J-50-3-B)、大河南幅(J-50-3-C)、镇厂幅(J-50-3-D)、龙门幅(J-50-3-A)区域地质调查联测报告.1981.
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