## 1 Introduction  
The seismic amplification effects in earthquake-prone areas need to be considered in building or structure designs. The relationship between the site condition and seismic ground motion has been researched for over one hundred years [1]. Pioneer researchers gathered a great deal of observational evidence to establish this relationship in the earlier studies [2]. Subsequently, many researchers [3, 4, 5, 6, 7, 8, 9, 10] attempted to evaluate the amplification characteristics of strong ground motions at a given site according to the acceleration records. For unrecorded locations, it is common to rely on the regression relationship obtained from the recorded results. This approach is regarded as reliable because the earthquake records [11] include all the influences of the earthquake source, transmission path and site features. However, for many local site amplification zones with no ground motion records, a simple regression relationship based on a large-sized site and inadequate data seems unreasonable. To overcome the lack of strong motion data to estimate the amplification factors at many local zones, an alternative to the seismic record method needs to be developed. The microtremor-based method, which is an empirical method, was first used by [PERSON] [12] and further developed by [PERSON] [13] for the site amplification analysis of cases without seismic records. By measuring the ambient noise or microtremors, the method can obtain the experimental transfer functions and predict the amplification factors of the site. Although the microtremor-based method can improve the surface amplification prediction for the area without seismic records, the research shows that there are significant differences in the predictions of the amplification characteristics under strong earthquakes. Signal processing has also become a key to prediction. The existing methods of processing signal data include wavelet transform methods [14; 15; 16], Fourier transform methods [17] and so on. As an alternative to the seismic record method, some researchers [18; 19] have used site response simulations based on the wave propagation theory and numerical methods to estimate the transfer functions and predict ground motions in particular regions. Compared with the empirical methods, numerical simulations [20] based on the wave propagation theory can establish an analytical model for the seismic response of a local site and adjust the parameters to predict the amplification factor of the site. However, simulation models still employ some major simplifications at present. Considering the heterogeneous structures of a local site [21; 22], seismologists [23; 24; 25] usually establish more realistic 2-D or 3-D wave propagation models to predict the ground motion and site amplification factors. These 2-D or 3-D models can reflect the effect of more site geology information. However, it is difficult to model seismic ground motions and predict site amplification in simulations of engineering problems, due to the high computational cost and complex simulation technology [26; 27; 28]. To improve prediction of the surface amplification characteristics in local areas, including basin regions, more and more local site stations have been established around the world for obtaining seismic observation records. Since the number of earthquake observation records in local domains has been increasing over the years, many researchers across the world prefer to develop amplification prediction models in a specific local site. Whether employing regression data from the observation records or computational simulations with predefined functions to predict the ground motion amplification factors, the aim is to develop reasonable prediction models or equations for the surface ground motion amplification factors in complex local sites.