Abstract
To investigate the seismic response of layered rock sites, a multidomain analysis method was proposed. Three finite element models with infinite element boundaries for layered sites were analysed. The results of this multidomain analysis show that stratum properties and elevation have an impact on wave propagation characteristics and the dynamic response of layered sites. Compared with the rock mass, the overlying gravel soil has a greater dynamic amplification effect at the sites. A time domain analysis parameter PGA(IMF) was proposed to analyse the effects of different strata on the seismic magnification effect of layered sites, and its application was also discussed in comparison with PGA. According to the frequency domain analysis, the interface of the rock mass strata has a low impact on the Fourier spectrum characteristics of the sites, but gravel soil has a great magnification effect on the spectrum amplitude in the high-frequency band (≥30 Hz) of waves. Moreover, the stratum properties have a great influence on the shape and peak value of the Hilbert energy and marginal spectrum at layered sites. When waves propagate from hard rock to soft rock, the peak value of the Hilbert energy spectrum changes from single to multiple peaks; then, in gravelly soil, the Hilbert energy spectral peak, its nearby amplitude and the amplitude in the high-frequency band (28–36 Hz) are obviously amplified. The frequency components and amplitude of the marginal spectrum become more abundant and larger from rock to gravelly soil in the high-frequency band (28–35 Hz).
Highlights
Western China has been prone to earthquakes in recent decades; the Wenchuan earthquake in 2008 was the largest and most widely distributed earthquake disaster in China [1,2]
Earthquake disasters mainly involve damage directly caused by fault dislocation and damage caused by strong earthquakes [3,4,5]. The former is generally in the blind area of the earthquake, which is difficult to prevent, while the latter is mainly affected by geological conditions, as has been verified by the Wenchuan earthquake [6,7]
In Southwest China, many important buildings are built on different types of sites with complex geological structures; in particular, layered sites are a common type of building site
Summary
Western China has been prone to earthquakes in recent decades; the Wenchuan earthquake in 2008 was the largest and most widely distributed earthquake disaster in China [1,2]. Celebi studied the intensity anomalies in the Chile and Mexico earthquakes in 1985 and California earthquakes in 1987 by using the traditional spectral ratio method based on the main and aftershock acceleration histories of earthquakes and thereby obtained the topography and soil layer amplification effect [24]. Based on the soil dynamic constitutive model, Jin et al proposed an explicit finite element method (FEM) for the seismic response of horizontally stratified sites under the condition of transmitting artificial boundaries [28]. Fan et al studied the seismic response of horizontally stratified sites under seismic conditions by using a shaking table test in the time-frequency domain [20]. A multidomain analysis method is used to investigate the seismic response of the layered sites under earthquake excitation (Figure 2). F4l.oFwlcohwarcthfoarrEt MfoDr EapMprDoaachp[p4r3o].ach [43]
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