含有单-粗糙面的走滑断层的滑动弱化不稳定性h
SLIP-WEAKENING INSTABILITY ON A STRIKE-SLIP FAULT WITH ASPERITY
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摘要: 本文研究了有限长度含有单一粗糙面的垂直走滑断层的滑动弱化不稳定性.我们假定断层强度在其深度方向是均匀的,而在走滑方向是不均匀的,即存在一个高强度段.并假定断层上的粗糙段及断层上的其它部分具有相同类型的本构律,只是峰值应力不同.断层周围的地壳材料用上、下表面应力自由的弹性平板来模拟.我们用有限元方法研究了理论位移场、应力场和应变场随远场位移的演变情况.此时,断层位移和摩擦应力并不是预先给定的,而是在求解过程中同时确定的.根据计算结果,我们比较了理论位移场及断层上摩擦应力分布在稳定和不稳定滑动情况时的差别.并与内部含有低强度段的走滑断层的场合做了比较.Abstract: In this paper, we have studied the slip-weakening instability on a finite and vertical strike-slip fault with asperity. We assumed that the fault strength is uniform in depth, but the strength is non-uniform in the strike direction, i.e., there is asperity on the fault. The segments with and without asperity of the fault follow the same type of constitutive law, but have different peak stresses. The material surrounding the fault is represented by elastic plates whose upper-surface and bottom are stress-free. We use finite element method to study the evolution of theoretical displacement, stress and strain fields that vary with a remote displacement. When the displacement and frictional stress are not given in advance but are determined in the solving process. According to the results, we have compared the differences of theoretical displacement and the distribution of frictional stress on the fault between stable and unstable slip. In addition, we have compared the results in this paper with known results for the strike-slip fault with a segment of lower strength.
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[1] Stuart, W. D., Strain softening prior to two——dimensional strike——slip earthquakes, J. Geophys. Res., 84,1063——1070, 1979.
[2] Stuart, W. D. and G. M. Mavko, earthquake instability on a strike——slip fault, J. Geophys. Ret., 84, 2153——2160, 1979.
[3] Reasenberg, P. and W. L. Ellsworth, Aftershocks of the Coyote Lake, California, earthquake of August 6,1979: A detailed study, J. Geophys. Res., 87, 10637——10655, 1982.
[4] Pechmann, J. C. and H. Kanamori, Waveforms and spectra of preshocks and aftershocks of the 1979 Imperial Valley, California earthquake: Evidence for fault heterogeneityl, J. Geophys. Res., 87, 10579——10597,1982.
[5] McGarr, A., D. Pollard, N. C. Gay and }W. O. Ortlepp, Observations and analysis of structures in exhumed mine——induced faults, Proceedings of Conference VIII, Analysis of Actual Fault Zones in Bedrock, U. S.Geol. Surv. Open File Rep., 79——1239, 101——120, 1979.
[6] Segall, P, and D. D. Pollard, Nucleation and growth of strike slip faults in granite, J. Geophys. Res., 88,555——568, 1983.
[7] Kanamori, H. and G. S. Stewart, Seismological aspects of the Guatemala earthquake of February 4, 1976,J. Geophys. Res., 83, 3427——3434, 1978.
[8] Kanamori, H., Use of seismic radiation to infer source parameters, Proceedings of Conference III, Fault Mechanics and Its Relation to Earthquake Prediction, Geol. Surv. Open File Rep. U. S., 78——380, 283——318, 1978.
[9] Das, S. and K. Aki, Fault plane with barriers: A versatile earthquake model, J. Geophyt. Res., 82, 5658——5670, 1977.
[10] Aki, K., Characterization of barriers on an earthquake fault, J. Geophys. Res., 84, 6140——6148, 1979.
[11] Mikumo, T. and T. Miyatake, Earthquake sequences on a frictional fault model with non——uniform strengths and relaxation times, Geophys. J. R. Astron. Soc., 59, 497——522, 1979.
[12] Ishiad, M. and H. Kanamori, The foreshock activity of the 1971 San Fernando, California earthquake, Bull.Seismol. Soc. Am., 68, 1265——1279, 1978.
[13] Ishiad, M. and H. Kanamori, Temporal variation of seismicity and spectrum of small earthquakes preced——ing the 1952 Kern County, California earthquake, Bull. Seismol. Sac. Am., 70, 509——528, 1980.
[14] Lay, T. and H. Kanamori, Earthquake doublets in the Solomon Islands, Phys. Earth Planet. Inter., 21,283——304, 1980.
[15] Dmowska, R. and V. C. Li, A mechanical model of precursory source processes for some large earthquake,Ceophys. Res. Lett., 9, 393——396, 1982.
[16] Niu Zhiren(牛志仁)and Zhang Yi(张逸),Analysis for slip——softening instability on a heterogeneous fault by finite element method,地震研究,8, 281——302, 1985.
[17] 陈运泰、黄立人、林邦慧、刘妙龙、王新华,用大地测量资料反演的1976年唐山地震的位错模式,地球物理学报, 22, 201——216, 1979[1] Stuart, W. D., Strain softening prior to two——dimensional strike——slip earthquakes, J. Geophys. Res., 84,1063——1070, 1979.
[2] Stuart, W. D. and G. M. Mavko, earthquake instability on a strike——slip fault, J. Geophys. Ret., 84, 2153——2160, 1979.
[3] Reasenberg, P. and W. L. Ellsworth, Aftershocks of the Coyote Lake, California, earthquake of August 6,1979: A detailed study, J. Geophys. Res., 87, 10637——10655, 1982.
[4] Pechmann, J. C. and H. Kanamori, Waveforms and spectra of preshocks and aftershocks of the 1979 Imperial Valley, California earthquake: Evidence for fault heterogeneityl, J. Geophys. Res., 87, 10579——10597,1982.
[5] McGarr, A., D. Pollard, N. C. Gay and }W. O. Ortlepp, Observations and analysis of structures in exhumed mine——induced faults, Proceedings of Conference VIII, Analysis of Actual Fault Zones in Bedrock, U. S.Geol. Surv. Open File Rep., 79——1239, 101——120, 1979.
[6] Segall, P, and D. D. Pollard, Nucleation and growth of strike slip faults in granite, J. Geophys. Res., 88,555——568, 1983.
[7] Kanamori, H. and G. S. Stewart, Seismological aspects of the Guatemala earthquake of February 4, 1976,J. Geophys. Res., 83, 3427——3434, 1978.
[8] Kanamori, H., Use of seismic radiation to infer source parameters, Proceedings of Conference III, Fault Mechanics and Its Relation to Earthquake Prediction, Geol. Surv. Open File Rep. U. S., 78——380, 283——318, 1978.
[9] Das, S. and K. Aki, Fault plane with barriers: A versatile earthquake model, J. Geophyt. Res., 82, 5658——5670, 1977.
[10] Aki, K., Characterization of barriers on an earthquake fault, J. Geophys. Res., 84, 6140——6148, 1979.
[11] Mikumo, T. and T. Miyatake, Earthquake sequences on a frictional fault model with non——uniform strengths and relaxation times, Geophys. J. R. Astron. Soc., 59, 497——522, 1979.
[12] Ishiad, M. and H. Kanamori, The foreshock activity of the 1971 San Fernando, California earthquake, Bull.Seismol. Soc. Am., 68, 1265——1279, 1978.
[13] Ishiad, M. and H. Kanamori, Temporal variation of seismicity and spectrum of small earthquakes preced——ing the 1952 Kern County, California earthquake, Bull. Seismol. Sac. Am., 70, 509——528, 1980.
[14] Lay, T. and H. Kanamori, Earthquake doublets in the Solomon Islands, Phys. Earth Planet. Inter., 21,283——304, 1980.
[15] Dmowska, R. and V. C. Li, A mechanical model of precursory source processes for some large earthquake,Ceophys. Res. Lett., 9, 393——396, 1982.
[16] Niu Zhiren(牛志仁)and Zhang Yi(张逸),Analysis for slip——softening instability on a heterogeneous fault by finite element method,地震研究,8, 281——302, 1985.
[17] 陈运泰、黄立人、林邦慧、刘妙龙、王新华,用大地测量资料反演的1976年唐山地震的位错模式,地球物理学报, 22, 201——216, 1979
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