利用非均匀细胞自动机模拟震级与应力降关系
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摘要
为解释实际观测资料震源破裂过程与自相似(分形)模型的不一致性,本文基于观测结果,构建了由81×81个细胞单元组成二维非均匀断层模型,并通过设计的细胞自动机模拟程序进行了模拟试验。研究结果表明:断层结构非均匀性是影响孕震过程特征的重要因素,而且地震强度分布并非简单的自相似。随着断层非匀质性增加,破裂过程出现由相对的脆性破坏向塑性破坏特征变化的趋势。利用细胞自动机不仅能较好地解释震级-频度关系中的大、小震级段低头现象,而且也可解释大震级事件具有相对恒定的应力降,得到了与实际观测研究相一致的结果。
In the paper,three kinds of heterogeneous faults with 81×81 cells are set up using celluar automata models and simulated for explaining the inconsistency between the observations and fractal-based model.The results show that the G-R relations behave not in simple self-similarity but multi-fractal,and with the increasing of heterogeneity the fracture process tends to turn from brittle to plastic behaviors.At the same time,using the models can explain not only the curvature at smaller and larger magnitudes in G-R relation but also the relatively constant stress drop for larger magnitude earthquake events.Fault structural heterogeneity plays a important role in earthquake preparation process.The results from computer simulation are consistent with observations from detailed seismicity studies.
In the paper,three kinds of heterogeneous faults with 81×81 cells are set up using celluar automata models and simulated for explaining the inconsistency between the observations and fractal-based model.The results show that the G-R relations behave not in simple self-similarity but multi-fractal,and with the increasing of heterogeneity the fracture process tends to turn from brittle to plastic behaviors.At the same time,using the models can explain not only the curvature at smaller and larger magnitudes in G-R relation but also the relatively constant stress drop for larger magnitude earthquake events.Fault structural heterogeneity plays a important role in earthquake preparation process.The results from computer simulation are consistent with observations from detailed seismicity studies.
引文
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[14]Sacks I S,Rydelek P A.Earthquake“quanta”as an explanation for observed magnitude and stressdrops[J].Bull Seism Soc Am,1995,85:808-813.
[15]Rice J R.Spatio-temporal complexity of slip on a fault[J].J Geophys Res,1993,98:9 885-9 907.
[16]罗灼礼,王伟君.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,2005,25(4):1-13.
[2]孙文福,顾浩鼎.具有独立过程的地震系列震级-频度分布[J].地震学报,1992,14(3):273-280.
[3]Scholz C H.The frequency-magnitude relation of microfracturing in rock and its relation to RFPA[J].Bull Seism Soc Am,1968,58:399-415.
[4]Mogi K.Some discussion on aftershock,foreshock and swarm[J].Bull Earthquake Res Inst,UnivTokoy,1963,41:615-658.
[5]蒋海昆,张流,周永胜.不同围压条件下花岗岩变形破坏过程中的声发射时序特征[J].地球物理学报,2000,46(6):812-822.
[6]Dysart P S,Snoke J A,Sacks I S.Source parameters and scaling relations for small earthquakes inMatsushiro region,southwest Honshu,Japan[J].Bull Seism Soc Am,1988,78:571-589.
[7]Taylor D W A,Snoke J A,Sacks I S,et al.Non-linear frequency-magnitude relationships for theHokkaido Conner,Japan[J].Bull Seism Soc Am,1990,80:340-353.
[8]Rydelek P A,Sacks I S.Testing the completeness of earthquake catalogues and the hypothesis ofself-similarity[J].Nature,1989,337:251-253.
[9]Scholz C H.The mechanics of earthquake and faulting[M].Cambridge University Press,1990.
[10]Bak P,Tang C,Wiesenfeld K.Earthquake as a self-organized critical phenomenon[J].J GeophsRes,1989,94:15 635-15 637.
[11]朱守彪,蔡永恩,刘杰,等.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),2006,42(2):206-210.
[12]Power W L,Tullis T E,Brown S R,et al.Roughness of natural fault surface[J].Geophys ResLett,1987,14:29-32.
[13]Wesnousky S G.Seismological and structural evolution of strike-slip faults[J].Nature,1988,335:340-343.
[14]Sacks I S,Rydelek P A.Earthquake“quanta”as an explanation for observed magnitude and stressdrops[J].Bull Seism Soc Am,1995,85:808-813.
[15]Rice J R.Spatio-temporal complexity of slip on a fault[J].J Geophys Res,1993,98:9 885-9 907.
[16]罗灼礼,王伟君.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,2005,25(4):1-13.
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