Simulation-Based Nonlinear Site Amplification Models for Western United States
Earthquake Spectra, cilt.42, sa.4, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 42 Sayı: 4
- Basım Tarihi: 2026
- Doi Numarası: 10.1002/esp4.70123
- Dergi Adı: Earthquake Spectra
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Compendex, Geobase
- Anahtar Kelimeler: response spectrum, site amplification, site effects, smoothed effective amplitude spectrum, Western United States
- Ankara Yıldırım Beyazıt Üniversitesi Adresli: Evet
Özet
This article presents one of the first nonlinear (NL) site amplification models relative to VS30 of 800 m/s for the Western United States (WUS) for both the smoothed effective amplitude spectrum (EAS), described as the orientation-independent horizontal-component Fourier amplitude spectrum (FAS) of ground acceleration, and the response spectra (RS). The amplification models were derived from a total of 286,254 1D site response analyses using randomizations of base-case VS profiles, generated through a new slowness model developed using VS measurements at California, and 600 recorded ground-motion pairs, scaled to match target spectra for 12 earthquake scenarios. The use of slowness model for generating VS randomizations yields a far broader suite of site conditions than from the preceding study employing only eight generic profiles. The simulation-based EAS- and RS-based NL amplification data exhibits more continuous behavior and alleviates the data sparsity in the low (<0.02 g) to mid (0.5–0.7 g) PGAr (peak ground acceleration at VS30 = 800 m/s) range as compared with prior work. Four NL mean amplification models with corresponding standard deviation relationships are proposed: two EAS-based named as N1EAS (VS30, EASr at 5 Hz), and N2EAS (VS30, frequency-specific EASr), and two RS-based models as N1RS (VS30, PGAr) and N2RS (VS30, pseudo-spectral acceleration at VS30 = 800 m/s (PSAr)). The N2 relationships exhibit lower standard deviation values of the residuals compared with their N1 counterparts. The compatibility between NL models’ predictions and observed NL amplification was assessed by incorporating NL relationships into an empirical ground motion model (GMM), resulting in within-event residuals of GMM closer to zero relative to those of GMM without NL terms, particularly for sites with 200 m/s < VS30 < 500 m/s. The amplification models are applicable for sites with VS30 ≥ 200 m/s and motions with PGAr ≤ 1.0 g or EASr≤ 0.3 g/s.