| In a short time, as we know, it is very difficult to acquire great advances in research field of predicting earthquake, however, major earthquake frequently occurs in the world and cause a great deal of economic losses and people's death. Therefore, it is easy to understand that government and society especially pay attention to seismic early warning system which is considered as affective measure of mitigating disaster caused by earthquake. In this paper, the research advances of earthquake early warning system is briefly summarized and the real-time processing technique of strong ground motion parameters is mainly researchedThe main achievements of this study could be summarized as follows:1. Trie concept of seismic early warning system (EWS) is discussed and the research advances is briefly summarized in this paper. Based on this, the practical scientific and technological problems of EWS are discussed. As the base of EWS, the rail-time processing technique of strong ground motion parameters is pointed out.2. The real-time processing technique of strong ground motion data is studied in this paper. Based on the research of Kanamori etc., the relation between the design parameters of recursive filter and its corresponding Low frequency cut-off frequency is obtained and quantitative phase adjustment is analyzed. By using this technique, the baseline of transmitting acceleration data in real time is adjusted, and the velocity and the displacement are integrated synchronistically. Based on this technique, a batch of data can be processed quickly.3. The calculation of response spectrum and Wood-Anderson seismogram can be considered as the response of single-degree-of-freedom (SDOF) system to ground motion. From the viewpoint of this, the forward difference method for calculating the SDOF system is analyzed in this paper. The accuracy and the existent problem of forward difference method are analyzed on the basis of comparing the transfer function of recursive formula with theoretical transfer function. The factitious damping is introduced in the forward method, and with the increasing of time interval and natural frequency, the method completely fails to reproduce the narrow-band response. Furthermore, the phase of system is changed greatly. To reproduce the narrow-band response, based on the thought of Kanamori etc., the damping ratio and natural period are modified. Through this adjustment, thenarrow-band response can be reproduced, but for some natural periods the adjustive damping ratio has become negative. The negative damping is strange and can not be explained by the equation of motion for SDOF system. Furthermore, in effective frequency-band, the transfer function can not accurately simulate the theoretical transfer function, especially for phase property. It shows that Kanamori's method is not a good one.4. In order to make it clear that the accuracy and the existent problem of typical algorithms of time-domain method, four numerical step-by-step methods are reviewed and compared in this paper. Based on the unified recursive formula, the four algorithms included in this study are the Central Difference Method, the Newrnark's method, Z-transform method, and Duhamel's step integral method. The accuracy, the phase and other existent problem are studied in this paper. It is proved in this paper that the recursive parameters b1and b2are relate to the poles of theoretical transfer function. Furthermore, the constraint condition of the transfer function at the zero frequency and the phase invariability condition of transfer function are presented. Based on the invariability of dynamic equation, the interrelation among recursive equation of relative displacement, velocity and acceleration are also obtained. At last, an algorithm for calculating response of SDOF system to ground motion is suggested.5. According to the analysis mentioned above, a set of recursive formula is found whose precision is equivalent to that of frequency-domain method. Only one undetermined parameter 8...
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