紫坪铺水库区域地壳Qs成像及其与渗透关系研究P315
  • 【摘要】

    利用衰减结构层析成像方法尝试对紫坪铺水库区域地壳Qs进行成像,获得该区浅层地壳静态及蓄水前、后的Qs变化特征,结合实验研究成果、岩体岩性、断裂构造、水文地质条件探讨库水的渗透作用及其对地壳介质的影响,对研究区内地震活动类型及发震成因的介质物性变化进行了讨论.研究结果表明:紫坪铺水库区域地壳Qs横向不均匀变化显著,库区周边近似存在低Qs值环形区域,主要包括水库东北、东南、西南、西北及库区中段五个区域... 展开>>利用衰减结构层析成像方法尝试对紫坪铺水库区域地壳Qs进行成像,获得该区浅层地壳静态及蓄水前、后的Qs变化特征,结合实验研究成果、岩体岩性、断裂构造、水文地质条件探讨库水的渗透作用及其对地壳介质的影响,对研究区内地震活动类型及发震成因的介质物性变化进行了讨论.研究结果表明:紫坪铺水库区域地壳Qs横向不均匀变化显著,库区周边近似存在低Qs值环形区域,主要包括水库东北、东南、西南、西北及库区中段五个区域.其中,水库东北、库区中段、西南低Qs区域与库水渗透关系密切,初步认为库水可能沿着通济场断裂中段和两端的岩石破碎带及节理、裂隙发育地区向地下渗透,使岩石孔隙中充满流体,内摩擦增大,地震波大大衰减,从而导致Qs值大幅下降.同时,在西南区诱发了水库小震群,在东北区和东南区诱发了部分水库小震群.另外,紫坪铺水库区域东北、东南、西南三个小震群基本位于高Qs值(低衰减)和低Qs值(高衰减)过渡区域,可能由于低Qs区地震波衰减大,不易积累能量,而高、低Qs值的过渡区域,介质介于"软"、"硬"之间,有可能积累应变能,孕育地震.当高、低Qs过渡区域岩石裂纹饱含水或部分含水后,水对裂纹边界起潮湿和润滑作用,降低了发震断层的抗剪强度,使滑动容易产生,从而诱发地震.The?crustal?Qs?values?are?imaged?in?Zipingpu?Reservoir?Area?to?obtain?shallow?crustal?characteristics?of?Qs?variation?before?and?after?the?impoundment?of?water?through?two-dimensional?seismic?attenuation?tomography.?The?infiltration?of?reservoir?water?and?its?impact?on?the?crust?are?investigated?with?experimental?findings,?rocks?lithology,?faults,?hydrological?and?geologicalconditions.?Simultaneously,?we?discussed?the?type?of?seismic?activity?and?physical?variety?of?medium?about?the?cause?of?earthquake?occurrence?in?the?area.?The?results?show?that?there?is?a?significant?lateral?heterogeneity?in?Qs?distribution?in?Zipingpu?Reservoir?Area.?Approximately,?there?are?low?Qs?value?annular?regions?surrounding?the?reservoir,?namely,?the?Qs?values?are?low?on?the?northeast,?southeast,?southwest,?northwest?sides?and?in?the?middle?part?of?the?reservoir.?Particularly,?the?Qs?values?variation?are?most?closely?related?to?fluid?infiltration?in?the?middle?part?and?on?the?northeast,?southwest?sides?of?the?reservoir.?We?consider?that?the?reservoir?water?infiltrates?through?from?the?middle?part?and?two?sides?of?the?rock?fracture?zones,?joints?and?fractured?regions?of?the?Tongjichang?faults,?filling?with?fluid?in?the?rock?pores,?increasing?the?internal?friction,?causing?significant?attenuation?of?seismic?waves,?resulting?in?a?substantial?decline?in?the?value?of?Qs,?inducing?small?earthquake?swarms?on?the?southwest?and?partly?on?northeast?and?southeast?sides.?The?small?earthquake?swarms?in?northeast,?southeast?and?southwest?regions?are?basically?converged?to?transitional?edge?regions?of?high?and?low?Qs?values.?This?is?perhaps?a?result?of?accumulation?of?strain?energy?in?weak?and?soft?zones.?After?full?or?partial?filling?of?water?in?rock?cracks,?there?are?wet?and?lubricating?effect?on?the?crack?boundary?in?the?high?and?low?Qs?transition?region,reducing?the?shear?strength?of?seismogenic?faults,inducing?earthquakes. 收起<<

  • 【作者】

    王惠琳  张晓东  周龙泉  徐晓枫  杨志高  卢显  李智蓉 

  • 【作者单位】

    中国地震局地震预测研究所/中国地震台网中心/海南省地震局/云南省地震局

  • 【刊期】

    地球物理学报 ISTIC PKU 2012年2期

  • 【关键词】

    衰减成像  Qs  流体渗透  紫坪铺水库  Attenuation tomography, Qs, Fluid infiltration, Zipingpu Reservoir 

  • 【基金项目】

    地震行业科研专项(200808036) 国家科技支撑计划(2008BAC38803)共同资助.