| 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 |
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| 引用本文： | 小山顺二,郑斯华.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[J].地震学报,1991,13(2):190-201. |
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| 作者姓名： | 小山顺二 郑斯华 |
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| 作者单位： | 1. 日本 980 仙台东北大学理学部地球物理学教室
2. 中国北京 100036 国家地震局分析预报中心 |
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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.
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| 关 键 词： | 破裂传播速度 地震烈度 断层不均匀性 |
SEISMIC INTENSITY DISTRIBUTION OF SHALLOW EARTHQUAKES DUE TO RUPTURE VELOCITIES AND FAULTING MODES |
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| Affiliation: | 1. Geophysical Institute, Faculty of Science, Tohoku University, Sendai, 980 Japan;
2. Center for Analysis and Prediction, Slate Scismological Bureau, Beijing 100036 China |
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| 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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