Fractal characterization and frequency properties of near-fault ground motions |
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| Authors: | Dixiong Yang Changgeng Zhang |
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| Institution: | 1. Department of Engineering Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian, 116023, China
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| Abstract: | This study explores the irregularity and complexity of strong earthquake ground motions from the perspective of fractal geometry, and constructs a relation with the frequency content of the ground motions. The box-counting fractal dimensions and five representative period parameters of near-fault ground motions from the Chi-Chi and Northridge earthquakes are calculated and compared. Numerical results indicate that the acceleration and velocity time histories of ground motions present the statistical fractal property, and the dominant pulses of near-fault ground motions have a significant influence on their box dimensions and periods. Further, the average box dimension of near-fault impulsive ground motions is smaller, and their irregular degree of wave forms is lower. Moreover, the box dimensions of ground motions reflect their frequency properties to a large extent, and can be regarded as an alternative indicator to represent their frequency content. Finally, the box dimension D of the acceleration histories shows a considerably negative correlation with the mean period T m. Meanwhile, the box dimension of the velocity histories D vel is negatively correlated with the characteristic period T c and improved characteristic period T gi. |
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| Keywords: | near-fault ground motions fractal property box-counting dimension frequency content indicators correlation analysis |
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