中国强震前兆地震活动图像机理的三维数值模拟研究
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摘要
建立了含有母体岩石、硬包体和随机分布的小裂纹的三维有限元模型,计算了包体和各层实体中的应力分布.利用最高应力破裂准则、释放破裂单元刚度生与死的方法,模拟强震前岩石的破裂和小震的空间分布特征.结果表明,文中三种模型都显示出强震前在孕震体即包体附近出现了高应力集中单元.它们是形成小震空区、条带和地震空间丛集图像的基础.随机裂纹的存在,有利于在孕震体(包体)外的裂纹端部应力集中,先发生小震,形成包围孕震包体的前兆地震活动图像,而包体中的应力逐渐增加,为发生强震提供了条件.包体的形状和几何位置是影响强震前兆地震活动图像形态的重要因素.引入材料的黏弹性,导致了其中应力随时间迅速减小和弹性层某些部位应力随时间的增加.但在本文设定的构造模型框架和介质参数下,下层黏弹性的存在对上层母体的应力随时间的增加影响不大.
In this paper, we build three 3D finite-element models including mother rock body, hard inclusions and randomly distributed cracks and computed the stress distribution within the mother body and hard inclusions. Using the failure criterion of maximum equivalent stress and the method of Element Birth and Death, the space distribution features of small earthquakes (micro cracks in rock) before a strong earthquake are simulated. The results show that high stress elements are distributed around the hard inclusion in all the three models, and they construct the earthquake gap, earthquake belt and cluster before the strong earthquake. Stress concentrations in the tips of randomly distributed cracks around the inclusion lead to the precursory seismicity pattern. Stress increase in the inclusion is a condition of strong earthquake occurrence. The shape and geometry of inclusion is an important factor which affects the precursory seismicity pattern. The visco-elasticity of material in the bottom of rock body led to decrease of stress with time in the bottom part and to increase of stress at some places of elastic layers. But the stress increase due to bottom material visco-elasticity is small in the model of this paper.
In this paper, we build three 3D finite-element models including mother rock body, hard inclusions and randomly distributed cracks and computed the stress distribution within the mother body and hard inclusions. Using the failure criterion of maximum equivalent stress and the method of Element Birth and Death, the space distribution features of small earthquakes (micro cracks in rock) before a strong earthquake are simulated. The results show that high stress elements are distributed around the hard inclusion in all the three models, and they construct the earthquake gap, earthquake belt and cluster before the strong earthquake. Stress concentrations in the tips of randomly distributed cracks around the inclusion lead to the precursory seismicity pattern. Stress increase in the inclusion is a condition of strong earthquake occurrence. The shape and geometry of inclusion is an important factor which affects the precursory seismicity pattern. The visco-elasticity of material in the bottom of rock body led to decrease of stress with time in the bottom part and to increase of stress at some places of elastic layers. But the stress increase due to bottom material visco-elasticity is small in the model of this paper.
引文
[1]梅世蓉,薛艳,宋治平等.华北北部强震前测震学的主要异常及其机理的初步解释.见:国家地震局预测预防司编.“地震短临预报的理论与方法”.北京:地震出版社,1997.495~504Mei S R,Xue Y,Song Z P,et a1.The main seismological anomaly before strong earthquake in North China and primaryinterpret of their mechanism.In:Division of Prediction and Precautionary.State Seismological Bureau eds.Theory and Methods of Short-Term/Imminent Earthquake Prediction(in Chinese).Beijing:Seismological Press,1997.495~504
[2]陆远忠,吴云,王炜等.地震中短期预报的动态图像方法.北京:地震出版社,2001,273~292Lu Y Z,Wu Y,Wang W,et a1.Dynamic pattern method for earthquake prediction of middle-short period(in Chinese).Beijing:Seismological Press,2001.273~292
[3]陈棋福主编.中国震例(1997~1999).北京:地震出版社,2003Chen Q F ed.Earthquake Case in China(1997~1999)(in Chinese).Beijing:Seismological Press,2003
[4]刘杰,刘桂萍,李丽等.基于大陆地震活动特点建立的简化动力学模型-细胞自动机模型.地震,1999,19(3):230~238Liu J.Liu GP,Li L,et al.Simplified dynamic model based on the characteristics of continental seismicity-cell automat model.Earthquake(in Chinese),1999,19(3):230~238
[5]张国民,耿鲁明,石耀霖.中国大陆强震轮回活动的计算机模拟研究.中国地震,1993,9(1):20~32Zhang G M,Geng L M,Shi Y L.A computer model for cycle activities of strong earthquake in continental seismic zones.Earthquake Researchin China(in Chinese),1993,9(1):20~32
[6]Mori T,Kawamura H.Simulation study of the one-dimensional Burridge-Knopoff model of earthquakes.J.Geophys.Res.,2006,111,B07302,doi:10.1029/2005JB003942
[7]Z ller G,Hainzl S,Ben-Zion Y,et al.Earthquake activity relatedto seismic cycles in a model for a heterogeneous strike-slip fault.Tectonophysics,2006,423:137~145
[8]Cianetti S,Giunchi C,Cocco M.Three-dimensional finite element modeling of stress interaction:An application to Landers and Hector Mine fault systems.J.Geophys.Res.,2005,110,B05S17,doi:10.1029/2004JB003384
[9]冯德益,舒立得,刘喜兰等.华北北部地震前兆场时空演化模型的非线性有限元研究.见:国家地震局预测预防司编.“地震短临预报的理论与方法”.北京:地震出版社,1997.505~513Feng D Y,Shu L D,Liu X L,et al.Research of temporal-spatial evolution model of earthquake precursor field in nonlinear finite element.In:Division of Prediction and Precautionary,State Seismological Bureau eds.Theory and Methods of Short-Term/Imminent Earthquake Prediction(in Chinese).Beijing:Seismological Press,1997.505~513
[10]宋治平,梅世蓉.强大地震前地震活动增强区及其力学研究.地震学报,1999,21(3):271~277Song Z P,Mei S R.Seismicity increase areas before strong earthquakes andtheir mechanismresearch.Acta Seismologica Sinica(in Chinese),1999,21(3):271~277
[11]刘庭金,唐春安,焦明若.含典型裂纹系硬包体试样破裂机制的数值试验.东北大学学报(自然科学版),2001,22(5):553~556Liu TJ,Tang C A,Jiao MR.Numerical tests onfracture mechanism of hard inclusion specimen with typical cracks.Journal of Northeastern University(in Chinese),2001,22(5):553~556
[12]叶金铎,陆远忠,蒋淳.含硬包体岩石破裂演化过程的声发射数值模拟.天津理工学院学报,2004,20(4):1~5Ye J D,Lu Y Z,Jiang C.The numerical modeling of acoustic emissionto the processes of rock damaged and evolution with high velocity body.Journal of Tianjin Institute of Technology(in Chinese),2004,20(4):1~5
[13]陈连旺,陆远忠,刘杰等.1966年邢台地震引起的华北地区应力场动态演化过程的三维粘弹性模拟.地震学报,2001,23(5):480~491Chen L W,Lu Y Z,Liu J,et al.Three dimensional viscoelasticsimulation on dynamic evolution of stressfieldin North Chinainduced by the1966Xingtai earthquake.Acta Seismologica Sinica(in Chinese),2001,23(5):480~491
[14]胡新亮,王俊国,刁桂苓等.一个特殊的地震空区.防灾减灾工程学报,2004,24(2):182~186Hu XL,Wang J G,Diao G L,et al.Aspecial seismic gap before DatongM5.6earthquake in Shanxi.Journal of Disaster Prevention and Mitigation Engineer(in Chinese),2004,24(2):182~186
[15]许昭永,王彬,赵晋明等.含硬包体试样微破裂图象演变过程的实验研究.地震学报,1997,19(3):317~322Xue Z Y,Wang B,Zhao J M,et al.Experimental studies on the evolution process of microcrack patterns in concrete samples.Acta Seismologica Sinica(in Chinese),1997,19(3):317~322
[2]陆远忠,吴云,王炜等.地震中短期预报的动态图像方法.北京:地震出版社,2001,273~292Lu Y Z,Wu Y,Wang W,et a1.Dynamic pattern method for earthquake prediction of middle-short period(in Chinese).Beijing:Seismological Press,2001.273~292
[3]陈棋福主编.中国震例(1997~1999).北京:地震出版社,2003Chen Q F ed.Earthquake Case in China(1997~1999)(in Chinese).Beijing:Seismological Press,2003
[4]刘杰,刘桂萍,李丽等.基于大陆地震活动特点建立的简化动力学模型-细胞自动机模型.地震,1999,19(3):230~238Liu J.Liu GP,Li L,et al.Simplified dynamic model based on the characteristics of continental seismicity-cell automat model.Earthquake(in Chinese),1999,19(3):230~238
[5]张国民,耿鲁明,石耀霖.中国大陆强震轮回活动的计算机模拟研究.中国地震,1993,9(1):20~32Zhang G M,Geng L M,Shi Y L.A computer model for cycle activities of strong earthquake in continental seismic zones.Earthquake Researchin China(in Chinese),1993,9(1):20~32
[6]Mori T,Kawamura H.Simulation study of the one-dimensional Burridge-Knopoff model of earthquakes.J.Geophys.Res.,2006,111,B07302,doi:10.1029/2005JB003942
[7]Z ller G,Hainzl S,Ben-Zion Y,et al.Earthquake activity relatedto seismic cycles in a model for a heterogeneous strike-slip fault.Tectonophysics,2006,423:137~145
[8]Cianetti S,Giunchi C,Cocco M.Three-dimensional finite element modeling of stress interaction:An application to Landers and Hector Mine fault systems.J.Geophys.Res.,2005,110,B05S17,doi:10.1029/2004JB003384
[9]冯德益,舒立得,刘喜兰等.华北北部地震前兆场时空演化模型的非线性有限元研究.见:国家地震局预测预防司编.“地震短临预报的理论与方法”.北京:地震出版社,1997.505~513Feng D Y,Shu L D,Liu X L,et al.Research of temporal-spatial evolution model of earthquake precursor field in nonlinear finite element.In:Division of Prediction and Precautionary,State Seismological Bureau eds.Theory and Methods of Short-Term/Imminent Earthquake Prediction(in Chinese).Beijing:Seismological Press,1997.505~513
[10]宋治平,梅世蓉.强大地震前地震活动增强区及其力学研究.地震学报,1999,21(3):271~277Song Z P,Mei S R.Seismicity increase areas before strong earthquakes andtheir mechanismresearch.Acta Seismologica Sinica(in Chinese),1999,21(3):271~277
[11]刘庭金,唐春安,焦明若.含典型裂纹系硬包体试样破裂机制的数值试验.东北大学学报(自然科学版),2001,22(5):553~556Liu TJ,Tang C A,Jiao MR.Numerical tests onfracture mechanism of hard inclusion specimen with typical cracks.Journal of Northeastern University(in Chinese),2001,22(5):553~556
[12]叶金铎,陆远忠,蒋淳.含硬包体岩石破裂演化过程的声发射数值模拟.天津理工学院学报,2004,20(4):1~5Ye J D,Lu Y Z,Jiang C.The numerical modeling of acoustic emissionto the processes of rock damaged and evolution with high velocity body.Journal of Tianjin Institute of Technology(in Chinese),2004,20(4):1~5
[13]陈连旺,陆远忠,刘杰等.1966年邢台地震引起的华北地区应力场动态演化过程的三维粘弹性模拟.地震学报,2001,23(5):480~491Chen L W,Lu Y Z,Liu J,et al.Three dimensional viscoelasticsimulation on dynamic evolution of stressfieldin North Chinainduced by the1966Xingtai earthquake.Acta Seismologica Sinica(in Chinese),2001,23(5):480~491
[14]胡新亮,王俊国,刁桂苓等.一个特殊的地震空区.防灾减灾工程学报,2004,24(2):182~186Hu XL,Wang J G,Diao G L,et al.Aspecial seismic gap before DatongM5.6earthquake in Shanxi.Journal of Disaster Prevention and Mitigation Engineer(in Chinese),2004,24(2):182~186
[15]许昭永,王彬,赵晋明等.含硬包体试样微破裂图象演变过程的实验研究.地震学报,1997,19(3):317~322Xue Z Y,Wang B,Zhao J M,et al.Experimental studies on the evolution process of microcrack patterns in concrete samples.Acta Seismologica Sinica(in Chinese),1997,19(3):317~322
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