新生地震构造带——马边地震构造带最新构造变形样式的初步研究
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摘要
以雷波地区为例,通过野外地质地貌调查,结合探槽技术以及年代测试结果,获得了有关马边地震构造带最新构造变形样式及其性质的初步认识。研究结果表明:马边地震构造带内的雷波地区存在一条北东东向雷波断裂带,它断错的最新地层时代在40ka左右,属晚更新世活动断裂;在活动性质上,为一条以右旋走滑运动为主的断裂。北北西向玛瑙断裂在第四纪风化壳中存在两次突然位错事件,在剖面上的错距分别为0.5m和>0.7m;最新错动面产状陡立,存在水平左旋位错的构造地貌证据。马边地震构造带上北东东向断裂与北北西断裂不是一种从属关系,而是在现代构造应力场条件下两组呈共轭关系的剪切断裂,它们代表了马边地震构造带最新构造变形样式,具新生性。马边地震构造带的破坏性地震以中强地震为主,具有频度高、成带性差等特点,这符合共轭状构造变形样式可能引起的地震活动特征。马边地震构造带位于青藏高原东缘南部,初步分析表明:一种受重力作用控制的中下地壳塑性流展模型,可以对该地区包括大凉山断裂带、安宁河断裂带以及鲜水河断裂带在内的断裂构造的活动习性做出较合理的解释。伴随着高原内部中下地壳物质持续向外流展,高原边界向外扩张形成新的边界,并表现为一条新生地震构造带。
By using the Leibo area as an example, a basic understanding of the latest deformation style in the Mabian seismictectonic belt has been abtained, based on the geologic and geomorphologic survey, and combined with trench technology and dating. The research results demonstrate the existence of an NEE-trending Leibo fault zone in the Leibo area. A faulted stratrum age is about 40 ka. The fault is a dextrak slip and active in late-pleistocene. The NNW-trending Manao fault exposes the Quaternary weathering crust, from which two displacement events can be recognized. Their displacement offsets are 0.5m and >0.7m in sections respectively. A steep plane of the offset provides the evidence of horizontal sinistral slip. The NEE- and NNW- trending faults in the Mabian seismic zone belong to one pair of conjugate shear faults in the modern tectonic stress-field, representing the latest deformation style of the Mabian seismotectonic zone. The disastrous earthquakes in the Mabian seismotectonic zone are characterized by moderate magnitudes, high frequency and weak zoning, and these are in agreement with features of earthquakes caused by conjugate tectonic frame. The Mabian seismotectonic zone is situated at the southern section of the eastern margin of the Tibetan Plateau. The research further shows that a ductile flow model in the middle-lower crust, controlled by gravity, can give a reasonable explanation about the active habits of faults, including the Dalianshan fault zone, Anninghe fault zone and Xianshuihe fault zone. With a continuous flow of the middle-lower crustal material inside the Tibetan Plateau, the Plateau boundary spread gradually outwards and a new boundary formed. Thus the boundary represents a newly-formed seismotectonic belt.
By using the Leibo area as an example, a basic understanding of the latest deformation style in the Mabian seismictectonic belt has been abtained, based on the geologic and geomorphologic survey, and combined with trench technology and dating. The research results demonstrate the existence of an NEE-trending Leibo fault zone in the Leibo area. A faulted stratrum age is about 40 ka. The fault is a dextrak slip and active in late-pleistocene. The NNW-trending Manao fault exposes the Quaternary weathering crust, from which two displacement events can be recognized. Their displacement offsets are 0.5m and >0.7m in sections respectively. A steep plane of the offset provides the evidence of horizontal sinistral slip. The NEE- and NNW- trending faults in the Mabian seismic zone belong to one pair of conjugate shear faults in the modern tectonic stress-field, representing the latest deformation style of the Mabian seismotectonic zone. The disastrous earthquakes in the Mabian seismotectonic zone are characterized by moderate magnitudes, high frequency and weak zoning, and these are in agreement with features of earthquakes caused by conjugate tectonic frame. The Mabian seismotectonic zone is situated at the southern section of the eastern margin of the Tibetan Plateau. The research further shows that a ductile flow model in the middle-lower crust, controlled by gravity, can give a reasonable explanation about the active habits of faults, including the Dalianshan fault zone, Anninghe fault zone and Xianshuihe fault zone. With a continuous flow of the middle-lower crustal material inside the Tibetan Plateau, the Plateau boundary spread gradually outwards and a new boundary formed. Thus the boundary represents a newly-formed seismotectonic belt.
引文
曹忠权,汪一鹏,殷秀华等.1993.马边地震构造带发震构造背景的初步研究.中国地震,9(4):373~383.
成尔林.1981.四川及其邻区现代构造应力场和现代构造运动特征.地震学报,3(3):231~241.
崔效锋;谢富仁;张红艳.2006.川滇地区现代构造应力场分区及动力学意义.地震学报,28(5):451~461.
刁桂岺,王绍晋,龙晓帆等.1995.永善-大关7.1级地震序列震源区应力场分析.华北地震科学,13(1):28~33.
丁国瑜,李永善.1979.我国地震活动与地壳现代破裂网络.地质学报,53(1):22~34.
国家地震局.1981.中国地震烈度区划工作报告.北京:地震出版社,378~383.
韩德润.1993.马边—永善地震带构造形式及地震特征.地震地质,15(3):253~260.
李玶.1979.四川马边地震——一个震群型发震构造的实例.川滇强震区地震地质调查汇编,北京:地震出版社:132~143.
刘正荣,雷素华,胡素华.1977.1974年5月11日云南永善-大关地震.地球物理学报,20(2):110~114.
谢富仁,祝景忠,梁海庆,等.1993.中国西南地区现代构造应力场基本特征.地震学报,15(4):407~417.
徐锡伟,张培震,闻学泽,等.2005.川西及其邻近地区活动构造基本特征与强震复发模型.地震地质,27(3):446~461.
张世民,聂高众,刘旭东,等.2005.荥经-马边-盐津逆冲构造带断裂运动组合及地震分段特征.地震地质,27(2):221~233.
张文佑.1984.断块构造导论.北京:石油工业出版社,97~95.
周玖,黄修武.1980.在重力作用下的我国西南地区地壳物质流.地震地质,2(4):1~10.
Barrows L,Langer C J.1981.Gravitational potential as a source ofearthquake energy.Tectonpphysics,76:237~253.
Clark M K,Royden L H.2000.Topographic ooze:Building theeastern margin of Tibet bylower crustal flow.Geology,28(8):703~706.
Goodacre A K,Haegawa,H S.1980.Gravitationally inducedstresses at structural boundaries.Can.J.Earth Sci.,17:1286~1291.
Royden L H,Burchfiel B C,King R W,et al.1997.Surfacedeformation and lower crustal flowin eastern Tibet.Science,276(5313):788~790.
Zhang P Z,Shen Z K,Wang M,et al.2004.Continuousdeformation of the Tibetan Plateau from global positioningsystemdata.Geology,32(9):809~812.
成尔林.1981.四川及其邻区现代构造应力场和现代构造运动特征.地震学报,3(3):231~241.
崔效锋;谢富仁;张红艳.2006.川滇地区现代构造应力场分区及动力学意义.地震学报,28(5):451~461.
刁桂岺,王绍晋,龙晓帆等.1995.永善-大关7.1级地震序列震源区应力场分析.华北地震科学,13(1):28~33.
丁国瑜,李永善.1979.我国地震活动与地壳现代破裂网络.地质学报,53(1):22~34.
国家地震局.1981.中国地震烈度区划工作报告.北京:地震出版社,378~383.
韩德润.1993.马边—永善地震带构造形式及地震特征.地震地质,15(3):253~260.
李玶.1979.四川马边地震——一个震群型发震构造的实例.川滇强震区地震地质调查汇编,北京:地震出版社:132~143.
刘正荣,雷素华,胡素华.1977.1974年5月11日云南永善-大关地震.地球物理学报,20(2):110~114.
谢富仁,祝景忠,梁海庆,等.1993.中国西南地区现代构造应力场基本特征.地震学报,15(4):407~417.
徐锡伟,张培震,闻学泽,等.2005.川西及其邻近地区活动构造基本特征与强震复发模型.地震地质,27(3):446~461.
张世民,聂高众,刘旭东,等.2005.荥经-马边-盐津逆冲构造带断裂运动组合及地震分段特征.地震地质,27(2):221~233.
张文佑.1984.断块构造导论.北京:石油工业出版社,97~95.
周玖,黄修武.1980.在重力作用下的我国西南地区地壳物质流.地震地质,2(4):1~10.
Barrows L,Langer C J.1981.Gravitational potential as a source ofearthquake energy.Tectonpphysics,76:237~253.
Clark M K,Royden L H.2000.Topographic ooze:Building theeastern margin of Tibet bylower crustal flow.Geology,28(8):703~706.
Goodacre A K,Haegawa,H S.1980.Gravitationally inducedstresses at structural boundaries.Can.J.Earth Sci.,17:1286~1291.
Royden L H,Burchfiel B C,King R W,et al.1997.Surfacedeformation and lower crustal flowin eastern Tibet.Science,276(5313):788~790.
Zhang P Z,Shen Z K,Wang M,et al.2004.Continuousdeformation of the Tibetan Plateau from global positioningsystemdata.Geology,32(9):809~812.
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