断层破裂传播速度与破坏性地震的烈度分布--浅源地震的断层不均匀性与短周期波动的多普勒效应
SEISMIC INTENSITY DISTRIBUTION OF SHALLOW EARTHQUAKES DUE TO RUPTURE VELOCITIES AND FAULTING MODES
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摘要: 地震的等震线不仅反映了地震的大小,而且也反映了地震断层过程的类型和破裂速度.单侧破裂的断层过程呈现出蛋型的等震线,而双侧破裂的断层过程呈现出椭圆的等震线,等震线的长轴与短轴之比对于破裂传播速度十分敏感.本研究利用理论等震线与观测结果相比较的方法,确定了1964年日本新地震、1983年日本海中部地震、1975年中国海城地震和1976年中国唐山地震的破裂传播速度、断层类型以及断层走向.得到的断层破裂速度是剪切波的0.7——0.9倍.这些值比用长周期地震波所确定的要稍大.产生这种差异的原因是:对烈度起主要影响的短周期地震波强烈地依赖于小尺度的断层不均匀破裂过程,以及局部的破裂传播的开始和终止;而由长周期波所得到的破裂速度却反映了在整个断层上破裂传播的平均过程.根据等震线图所得出的断层类型及断层走向与其它独立方法的结果相一致.这意味着本方法可以应用于推断某些历史地震的断层类型、破裂传播速度及破裂传播方向.Abstract: Isoseismals not only represent seismic intensity distributions but also represent earthquake source size, faulting mode, and rupture velocity of fault propagation. Unilateral faulting forms egg-shaped isoseismals, while bilateral faulting forms elliptical ones. It is found that the ratio of major to minor axes of isoseismals is sensitive to rupture velocity. Rupture velocity, faulting mode, and fault trend have been determined from the seismic intensity maps of the 1964 Niigata and the 1983 Japan Sea earthquakes in Japan and the 1975 Haicheng and the 1976 Tangshan earthquakes in China by matching theoretical isoseismals. Rupture velocities thus estimated are mostly 70 to 90% of shear wave velocity They are a little higher than those obtained from long-period seismic waves. This difference would be considered as follows: Short-waves which determine the seismic intensity are strongly dependent on the rupture of small-scale, fault heterogeneities and on the jerky onsets and terminations of local rupture propagations. On the other hand, rupture velocity from long-waves represents an average rupture propagation along the whole fault length. Faulting mode and fault trend estimated from seismic intensity maps match with the earthquake faulting independently determined. This suggests that the present method could be applicable to some historical earthquakes with known seismic intensity distribution to obtain detailed information on the faulting process.
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[2] 宇佐美翁夫,1987,新摄日本被害地震捻览.束京大学出版会.束京,1——434,
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[4] Cervenj., V., Popov, M. M.and Psencik, L, 1982. Computation of wave fields in iahomogeneous media——Gaussian beam approach. Geophyr. J. R. astr. Soc., 70, 109——128.
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[26] Zhou, H., Allen, C. R. anti Kanamori, H., 19836, Rupture complexity of the 1970 Tonghai and 1973 Luhuo earthquakes, China, from P——wave inversion, and relationship to surface faultingBull. Seism. Sot. Amen, 73, 1585——1597.
[27] Kanamori, H. and Anderson, D. L., 1975. Theoretical basis of some empirical relations in seisinology. Bull. Seirm. Sot. Amen, 65, 1073——1095.
[28] Brune, J. N. and King, D. Y., 1967. Excitation of mantle Rayleigh waves of period 100 seconds as a function of magnitude. Bull. Seism. Soc. Amen, 57, 1355——1385.
[29] Koyama, J., Takemura, M. and Suzuki, Z., 1982. A scaling model for quantification of rthquakes in anal near Japan. Tectonophysicr, 84, 3——16.
[30] Koyama, J., 1987. Focal mechanism of tsunami and tsunamigenic earthquakes. Yroc. Intern.Tsunami Symp. 1987, in press, lUGG.
[31] Aki, K., 1966. Generation and propagation of G waves from the Niigata earthquake of June 16, 1964. Bull. Earzhg. Res. Inst., Tokyo Ilniv., 44, 23——88.
[32] 7hou, H., Liu, H. L. and Kanamori, H., 1983. Source process of large earthquakes along the Xianshuihe fault in Southwestern China. Bull. Seism. Sac. timer 73, 537——551.
[33] Zheng, S., 1983. Seismic moment tensor inversion of earthqaukes in and near the Tibetan plateau.博士学位论文,束北大学理学部,1——187,[1] 国家地晨局,1979.中国地震等烈度腺图集,地震出版社.北京,1——107,
[2] 宇佐美翁夫,1987,新摄日本被害地震捻览.束京大学出版会.束京,1——434,
[3] Campillo, M. and Bouchon, M., 1983. A theoretical study of the radiation from small strikeslip earthquakes at close distances. Buld. Seism. Soc. Amer,73, 83——96.
[4] Cervenj., V., Popov, M. M.and Psencik, L, 1982. Computation of wave fields in iahomogeneous media——Gaussian beam approach. Geophyr. J. R. astr. Soc., 70, 109——128.
[5] Trifunac, M, D. and Brady, A. G., 1975. On the correlation of seismic intensity scales with the peaks of recorded strong ground motion. Bull. Seism. Sac. Amer. 65, 139——162.
[6] Koyama, J., 1985. Earthquake source time——function from coherent and incoherent rupture. Tectonophyrics, I18, 227——242.
[7] 小山顺二,1987,短周期地震波。方位依存性.地震2,40,397——404,
[8] Koyama, J. and Zheng, S. H., 1985. Excitation of short——period body——waves by great earthquakes. Phys. Earth Planet, later., 37, 108——123.
[9] 小山顺二,1988,震度分布t断屠遐勤一加速度。方位依存性.地震,41,79——87,
[10] 小山顺二、泉谷恭男,1988.最大加速度、1964年新渴地震乏1983年日本海中部地震.地震,41,1——8
[11] Boore, D. M., 1983. Stochastic simulation of high——frequency ground motions based on seismological models of the radiated Koyama, J. and Shimada. N spectra. Bull. Seism. Sac, Amer., 73, 1865——1894.
[12] Physical basis of earthquake magnitudes: An extreme value of seismic amplitudes from incoherent fracture of random fault patches. Phyr. Earth Planet.Inter., 40, 301——308.
[13] Gutenberg, B. and Richter, C. F., 1942. Earthquake magnitude, intensity, energy, and acceleraLion. Bull. Seism. Soc. Amen, 32, 163——191.
[14] Hirasawa, T 1965. Source mechanism of the Niigata earthquake of June 16, 1964, as derived from body waves. J. Phys. Earth., 13, 35——66.
[15] 茅野一郎 1973.近地地震。震源决定地震。地震研究所研究.束京大学,12,83——98,
[16] Kawasumi, H. and Sato, Y., 1968. Intensity of Niigata earthquake as determined from questionnaires. General Rep. Niigata Earthq. 1964. Tokyo Elec. Eng. Coll., 175——179.
[17] 河角店X1973.地震炎害,共立出版,束京.1——276.
[18] 梅世蓉X1982, 1976年唐山地展,地震出版社,北京.1——459,
[19] Butler, R., Stewart, G. S, and Kanamori, H., 1979. The July 27, 1976 Tangshan, China earthquake——A complex sequence of intraplate events. Bull. Seism. Soc. Amer. 69, 207——220.
[20] Chen, P. and Nuttli, O. W., 1984. Estimates of magnitudes and short——period :wave attenuation of Chinese earthquakes from modified ,Mercalli intensity data. Bull. Seism. Soc. Amen, 74,957——9ti8.
[21] ;,ato, T Kosuga, M Tanaka, K, and Sato, H., 1986. Aftershock distribution the 1983 Nihonkai——chubu (Japan Sea) earthquake determined from relocated hypocenters. J. Phys. Earth.34, 203——223.
[22] 太田裕、镜味洋史、俊藤典俊、同田成幸、掘田淳、1984, 4, 2, 2, 1983年日本海中部地震,北北海道地域市时村震度稠查.1983年日本海中部地震稠查研究 176——179,
[23] Hashida, T, and Shimazaki, K., 1987. Predicting JMA seismic intensities based on 3——D attenuanon structure and suface amplifying factor: The Tohoku district, Japan. J. Phys. Earrh., 35,367——379.
[24] Cipar, J., 1979. Source processes of the Haicheng, China earthquake from observations of Ptnd S waves. Bull. Seism. Soc. Amen, 69, 1903——1916.
[25] 蒋凡,1978.海城地震,地震出版社,北京.1——90,
[26] Zhou, H., Allen, C. R. anti Kanamori, H., 19836, Rupture complexity of the 1970 Tonghai and 1973 Luhuo earthquakes, China, from P——wave inversion, and relationship to surface faultingBull. Seism. Sot. Amen, 73, 1585——1597.
[27] Kanamori, H. and Anderson, D. L., 1975. Theoretical basis of some empirical relations in seisinology. Bull. Seirm. Sot. Amen, 65, 1073——1095.
[28] Brune, J. N. and King, D. Y., 1967. Excitation of mantle Rayleigh waves of period 100 seconds as a function of magnitude. Bull. Seism. Soc. Amen, 57, 1355——1385.
[29] Koyama, J., Takemura, M. and Suzuki, Z., 1982. A scaling model for quantification of rthquakes in anal near Japan. Tectonophysicr, 84, 3——16.
[30] Koyama, J., 1987. Focal mechanism of tsunami and tsunamigenic earthquakes. Yroc. Intern.Tsunami Symp. 1987, in press, lUGG.
[31] Aki, K., 1966. Generation and propagation of G waves from the Niigata earthquake of June 16, 1964. Bull. Earzhg. Res. Inst., Tokyo Ilniv., 44, 23——88.
[32] 7hou, H., Liu, H. L. and Kanamori, H., 1983. Source process of large earthquakes along the Xianshuihe fault in Southwestern China. Bull. Seism. Sac. timer 73, 537——551.
[33] Zheng, S., 1983. Seismic moment tensor inversion of earthqaukes in and near the Tibetan plateau.博士学位论文,束北大学理学部,1——187,
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