断层结构非均匀性对地震活动性影响的细胞自动机模拟
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摘要
基于断层强度分布的非均匀性,构建了由81×81个细胞单元组成的4种不同匀质度及其各自6种不同随机构型共计24个非均匀二维单断层模型样本,并通过设计的细胞自动机模拟程序,在保持其它模拟参数不变的条件下对它们进行了模拟试验.研究结果表明,随着断层结构非匀质度的增加,其宏观变形破坏行为由相对脆性向塑性变化;地震序列类型依次表现出主震型、前震-主震-余震型和震群型;震级分布表现出非均匀性依次减小;地震发生在时间上表现为一种确定性的随机过程,即小震随机、中强地震丛集和大震准周期的特点.此外,结构几何分布的随机性也对地震序列的特点有较显著的影响,但这种随机差异性随着结构非匀质程度的增加逐渐减小.
A 2-D cellular automata fault model with 81×81 cells was constructed to test its seismicity performance. In a series of tests 4 kinds of fault strength heterogeneity and 6 different strength geometrical distributions were taken. With the model simulation we analyzed how the fault structure heterogeneity affects macroscopic fault failure behavior and generated seismic sequence type. The results show that with increasing degree of heterogeneity the macroscopic deformation and fracture process present from brittle to plastic behavior, and produce 3 different types of seismic sequence, i.e., main shock type, foreshock-main shock-aftershock type and swarm type. In the same time, with increasing fault strength heterogeneity the fracture size distribution more regularly follows the G-R relation. Besides, temporarily the events occur in a certain random process, that is, small events appear randomly, medium size events occur in clusters and large ones emerge quasi-periodically. The event clustering and quasi-periodic occurrences become less significant with the fault heterogeneity increasing. It is also found that the randomness of structural geometric variation may affect characteristics of seismic sequences, but the difference in randomness becomes weaker as degree of heterogeneity increases.
A 2-D cellular automata fault model with 81×81 cells was constructed to test its seismicity performance. In a series of tests 4 kinds of fault strength heterogeneity and 6 different strength geometrical distributions were taken. With the model simulation we analyzed how the fault structure heterogeneity affects macroscopic fault failure behavior and generated seismic sequence type. The results show that with increasing degree of heterogeneity the macroscopic deformation and fracture process present from brittle to plastic behavior, and produce 3 different types of seismic sequence, i.e., main shock type, foreshock-main shock-aftershock type and swarm type. In the same time, with increasing fault strength heterogeneity the fracture size distribution more regularly follows the G-R relation. Besides, temporarily the events occur in a certain random process, that is, small events appear randomly, medium size events occur in clusters and large ones emerge quasi-periodically. The event clustering and quasi-periodic occurrences become less significant with the fault heterogeneity increasing. It is also found that the randomness of structural geometric variation may affect characteristics of seismic sequences, but the difference in randomness becomes weaker as degree of heterogeneity increases.
引文
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Bak P,Tang C,Wiesenfeld K.1989.Earthquake as a self-organized critical phenomenon[J].J Geophs Res,94(B11):15635-15637.
Ben-Zion Y,Rice J R.1993.Earthquake failure sequences along a celluar fault zone in a three-dimensional elastic solid containing asperity and nonasperity regions[J].J Geophys Res,98(B8):14109-14131.
Kagan Y Y,Jackson D D.1991.Long-term earthquake clustering[J].Geophys J Int,104(1):117-133.
Main I G.1996.Statistical physics,seismogensis and seismic hazard[J].Rev Geophys,104(B3):4755-4768.
Mogi K.1963.Some discussion on aftershock,foreshock and swarm[J].Bull Earthq Res Inst,Univ Tokyo,41(4):615-658.
Rundle J B,Klein W,Gross S.1999.Physical basis for statistical patterns in complex earthquake populations:Models,predictions and tests[J].Pure Appl Geophys,155(2-4):575-607.
Steacy S J,McCloskey J.1998.What controls an earthquakes size?:Results from a heterogeneous celluar automaton[J].Geophys J Int,133(1):F11-F14.
焦明若,唐春安,张国民,石耀霖,候万凯.2003.细观非均匀性对岩石破裂过程和微震序列类型影响的数值实验研究[J].地球物理学报,46(4):659-666.
李纲,刘杰,傅征祥,刘桂萍.2004.运用细胞自动机模型模拟强震前地震活动时间演化过程[J].地震,24(1):34-41.
李锰,杨峰.2010.结构非均匀性理论模型的关联维描述[J].内陆地震,24(3):193-198.
刘桂萍,傅征祥,刘杰.2000.摩擦时间依从的地震活动性细胞自动机模型[J].地球物理学报,43(2):204-211.
刘桂萍,傅征祥.2001.地震强度分布不均匀性的摩擦时间依从CA模型[J].地震,21(2):22-28.
刘杰,刘桂萍,李丽,张国民.1999.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[J].地震,19(3):230-238.
陆远忠,吕悦军,郑月君.1994.强震孕育后期地震活动演化的定量表征[J].中国地震,10(增刊):12-17.
罗灼礼,王伟君.2005.震级变异系数与地震序列类型、性质的统计物理特征和早期判定方法的研究[J].地震,25(4):1-13.
唐春安,刘红元,秦四清,杨志法.2000.非均匀性对岩石介质中裂纹扩展模式的影响[J].地球物理学报,43(1):116-120.
王林瑛,陈佩燕,吴忠良,白彤霞.2005.前震特征及其识别研究[J].地震学报,27(2):171-177.
朱守彪,蔡永恩,刘杰,石耀霖.2006.利用三维细胞自动机模拟地震活动性[J].北京大学学报:自然科学版,42(2):206-210.
Bak P,Tang C,Wiesenfeld K.1989.Earthquake as a self-organized critical phenomenon[J].J Geophs Res,94(B11):15635-15637.
Ben-Zion Y,Rice J R.1993.Earthquake failure sequences along a celluar fault zone in a three-dimensional elastic solid containing asperity and nonasperity regions[J].J Geophys Res,98(B8):14109-14131.
Kagan Y Y,Jackson D D.1991.Long-term earthquake clustering[J].Geophys J Int,104(1):117-133.
Main I G.1996.Statistical physics,seismogensis and seismic hazard[J].Rev Geophys,104(B3):4755-4768.
Mogi K.1963.Some discussion on aftershock,foreshock and swarm[J].Bull Earthq Res Inst,Univ Tokyo,41(4):615-658.
Rundle J B,Klein W,Gross S.1999.Physical basis for statistical patterns in complex earthquake populations:Models,predictions and tests[J].Pure Appl Geophys,155(2-4):575-607.
Steacy S J,McCloskey J.1998.What controls an earthquakes size?:Results from a heterogeneous celluar automaton[J].Geophys J Int,133(1):F11-F14.
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