On Near‐Fault Ground Motion Characteristics Through Multi‐Scale Method

Abstract

AbstractGround motion recorded in near‐fault regions that possesses long‐period pulse is a special destructive ground motion. For further research on the constituent of low‐frequency component and its pulse characteristics, a decomposition method based on multi‐scale analysis method in wavelet theory is proposed. Accordingly, an intact ground motion can be decomposed into multiple components having different frequency contents. Firstly, the validity and accuracy of this decomposition method are elaborated in three aspects which are the frequency domain, time domain and the dynamic response. Secondly, a suite of 53 typical near‐fault ground motions recorded from 12 recent major earthquakes are decomposed through this method, then a total of 266 ground motion components are obtained. Thirdly, a quantitative statistical study of the variation of the long period components contained in near‐fault ground motions with the impact of site and rupture distance is carried out in this paper. Lastly, predominant component is used as the simplified model of dominant pulse, and the variation of velocity amplitude and pulse period with the impact of magnitude and rupture distance is presented. It is concluded that: the period of the component which is the main ingredient of near‐fault ground motions is within 0.2∼2 s; the long‐period component contained in soil ground motions is richer than in rocks; in near‐fault area where the rupture distance is 0∼15 km, the proportion of the long period component decreases along with rupture distance increase; PGVp, the velocity amplitude of predominant component, is about 0.6 times of PGV, the velocity amplitude of original ground motion, and a clear linear relation is found between them; PGVp decreases as rupture distance increases, and will be larger in great earthquakes; logarithm of the pulse periods Tp increases linearly as magnitude increases.