Site amplification models using relatively simple site proxies (e.g., averaged shear‐wave velocity and soil depth) do not capture site‐specific resonance effects observed at soil sites having a high shear‐wave velocity impedance contrast. We present a model to supplement ergodic site amplification equations to consider these effects (i.e., our model is additive to ergodic equations in a natural log sense). The model is conditional on properties of horizontal‐to‐vertical (H/V) spectral ratios recorded at the site of interest and consists of a frequency‐domain pulse function parameterized by site period, pulse amplitude, and pulse width. H/V spectral ratio peaks are observed in 97% of sites in our data set. When no appreciable H/V spectral ratio peak is present, we provide a broadband adjustment to the ergodic model. Because H/V spectral ratios are typically measured under small‐strain (effectively viscoelastic) conditions but applied in engineering practice for stronger shaking conditions, our model modifies site period for nonlinear site‐response effects. The model adapts in an empirical manner H/V spectral ratio attributes measured from Fourier amplitude spectral ratios to horizontal response spectral amplification using a data set from Japan composed of sites having sufficient recordings to produce stable mean H/V spectral ratios. Compared to an ergodic model that does not consider H/V spectral ratios, application of the proposed model reduces natural log within‐event standard deviation by an average of 0.04.

A series of one-dimensional (1-D) site response analyses were performed using the nonlinear (NL) and equivalent linear (EQL) approaches to assess the applicability of the Vietnamese earthquake-resistance design code TCVN 9386: 2012. Six soil profiles were selected from three districts in Hanoi (Vietnam). A number of ground motions compatible with the rock design spectrum were used as input for carrying out analyses. The results highlight that the calculated response is higher than the design spectrum for site class C and lower for site class D. The normalized response spectra of the EQL approach results are higher than those of the NL approach. Moreover, the peak ground accelerations at the surface from EQL analyses are greater than those of the NL method because the latter generates a higher amount of nonlinearity. The results from the NL approach also illustrate that the deamplification phenomenon occurs in the soft soils of the Hanoi region (e.g., soil profile P3 and P5 of site class D). Additionally, the shear strains calculated from the NL method are closely matched with those from the EQL method, the difference between them increasing with a decrease in soil stiffness.