Preliminary Research On The Computational Method And Standards Of Seismic Intensity

According to current Chinese seismic intensity scale, there is a relationship between seismic intensity and two physical parameters (the peak ground acceleration and the peak ground velocity) respectively. The probability of the calculated instrument intensity agrees with that of site investigation are low when the two physical parameters are used to assess the seismic intensity. In practice, it is significant to study how to calculate the instrument intensity. Based on this problem, the thesis has done the following work.1 The acceleration records of 88 strong ground motions in the Wenchuan seismic sites whose seismic intensity arrange fromâ…¥toâ…¨are selected. Then the velocity records are simulated based on the acceleration records. In addition, both peaks of the acceleration records and the velocity records are calculated. Finally, the intensities of stations'spots are assessed by the two physical standards of Chinese seismic intensity scale, and the results of the two methods are quite different from the site investigation.2 The thesis calculates the following ten seismic ground motion parameters: the Peak Ground Acceleration (PGA), the Peak Ground Velocity (PGV), the 90% energy duration (Td) and so on. To find some representative seismic ground motion parameters involved in intensity assessment, the thesis calculate the correlation coefficient between these parameters. These parameters can be divided into three groups through the analysis of the correlation coefficient, considering the case of convenient application, this article initial choice PGA,PGV and Td as physical assessment criterion of seismic intensity in each group. Then the relationships between seismic intensity and PGA, PGV, Td are simulated respectively, the results of simulation show that the correlation coefficients between PGA and seismic intensity are as high as that of PGV, but the correlation coefficients between Td and seismic intensity is relatively low. Based on the results, the PGA and PGV are selected as the physical assessment criteria of seismic intensity. The thesis separately assessed the intensities of the stations site by the two parameters according to current Chinese seismic intensity scale. The probability of the calculated instrument intensity agrees with that of site investigation by PGA is 35% and by PGV is 50%,the calculated result of PGA is lower than the result of PGV obviously,but both probability of calculated intensity agrees with that of site investigation lower that we want. To solve this problem, a comprehensive evaluation seismic intensity method is given by analyzing the results of assessment independently. We find:The results of the comprehensive determination method PGA and PGV is better than before. And the instrument intensity is closer to the investigation intensity effectively 3 Based on the method of the Japanese Instrument intensity calculation, the thesis obtain an Instrument intensity criterion in line with our current assessment criterion broadly, and testing with the records of wenchuan earthquake. We find:The results of the comprehensive determination method PGA and PGV and this instrument intensity criterion agrees with that of site investigation all above the probability of 60%. At the same time,?this article also carried out checking with the Chi-Chi earthquake data, the result shows: the calculated result of PGA is better than the results of other methods. The comprehensive determination method of PGA and PGV calculate simply, then, the Japanese instrument intensity method is more comprehensive, assessment results are also better stability, before further study the method of this peper advised, the Japanese methods could be applied in practice.In the conclusion part, the summary is given.