摘要:
首先对地幔对流、大陆漂移和地震起源的机制做了尝试性分析,给出一个简单的力学解释。然后,考虑不同的震源类型,破裂传播以及岩体性质,探讨了震源机制对地面运动和波传播的影响。根据间断(阶跃)波理论阐明了至少应该有两个物理参量才能表征地震烈度,因为在震源处同时有应力阶跃和质点速度阶跃发生。也阐明了断层的破裂速度连同断层面积一起应是第三个重要影响参量,因为它对震源处卸载的时间函数的形式有决定性的影响。由于断层破裂是一个瞬间卸载过程,并引起应力和速度阶跃,而现行惯用的一些概念均未考虑到这一点,所以笔者对工程地震和地震工程中若干概念提出了一些看法,意在引起学术界讨论
关键词:
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波传播
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破裂传播
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震源机制
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地运动
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卸载波
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阶跃波
Abstract:
A tentative analysis of the mechanism of mantle circulation flow, continent drifting and earthquake origin is first clearly made, giving a simple mechanics-based explanation of the nature. Then the effects of earthquake mechanism on ground motion and wave propagation are delineated in a simple manner by accounting for the different types of earthquake source, break propagation, as well as the variations of rock property. It is shown on the basis of principles of mechanics that at least two physical parameters characterizing the seismic intensity must be specified because at the earthquake source two parameters, the stress jump and the velocity jump of particle motion, should act simultaneously whenever a sudden break occurs according to the discontinuous (jump) wave theory. While it is shown that the break propagation speed C b together with the break plane area may be the third key parameter influencing definitely the time form of unloading function at the source. Since the fault break is an unloading process in the sense of mechanics and the break lead to stress jump and velocity jump so some concepts so far defined seem not exact or even of misunderstanding. Thus some comments on a number of basic concept in engineering seismology and earthquake engineering are made tentatively, aiming at arising an academic discussion.
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