A Nonlinear Site Amplification Model for the Horizontal Component Developed for Ground-Motion Prediction Equations in Japan Using Site Period as the Site-Response Parameter

ABSTRACT This article presents a nonlinear site amplification model for ground-motion prediction equations (GMPEs), using site period as site-effect proxy based on the measured shear-wave velocity profiles of selected KiK-net and K-NET sites in Japan. This model was derived using 1D equivalent-linear site-response analysis for a total of 516 measured soil-site shear-wave velocity profiles subjected to a total of 912 components of rock-site records. The modulus reduction and damping curves for each soil layer were assigned based on the soil-type description for a particular layer. The site period and site impedance ratio affect both the linear and nonlinear parts of this study, and were used as the site parameters in the 1D amplification model. A large impedance ratio enhances the amplification ratios when the site responds elastically and enhances the nonlinear response when the site develops a significant nonlinear response. The effects of moment magnitude and source distance on the linear part of the 1D amplification model were also incorporated in the model. To implement the 1D amplification model into GMPEs, a model adjustment is required to match the GMPE amplification ratio at weak motion and to retain the nonlinear amplification ratio at the strong motion of the 1D model. The two-step adjustment method by Zhao, Hu, et al. (2015) was adopted in this study with significant modifications. It is not possible to obtain a credible second-step adjustment parameter using the GMPEs dataset only. We proposed three methods for calculating the scale factors. Method 1 is a constant angle in a 30°–60° range for all spectral periods; method 2 was based on the GMPE dataset and 1-D model parameters; and method 3 was based on the strong-motion records used for the 1D site modeling. A simple second-step adjustment factor leads to smoothing amplification ratios and soil-site spectrum.

Multi-method site characterization to verify the hard rock (Site Class A) assumption at 25 seismograph stations across Eastern Canada

Site characterization is a crucial component in assessing seismic hazard, typically involving in situ shear-wave velocity ( VS) depth profiling, and measurement of site amplification including site period. Noninvasive methods are ideal for soil sites and become challenging in terms of field logistics and interpretation in more complex geologic settings including rock sites. Multiple noninvasive active- and passive-seismic techniques are applied at 25 seismograph stations across Eastern Canada. It is typically assumed that these stations are installed on hard rock. We investigate which site characterization methods are suitable at rock sites as well as confirm the hard rock assumption by providing VS profiles. Active-source compression-wave refraction and surface wave array techniques consistently provide velocity measurements at rock sites; passive-source array testing is less consistent but it is our most suitable method in constraining the rock VS. Bayesian inversion of Rayleigh wave dispersion curves provides quantitative uncertainty in the rock VS. We succeed in estimating rock VS at 16 stations, with constrained rock VS estimates at 7 stations that are consistent with previous estimates for Precambrian and Paleozoic rock types. The National Building Code of Canada uses solely the time-averaged shear-wave velocity of the upper 30 m ( VS30) to classify rock sites. We determine a mean VS30 of ∼ 1600 m/s for 16 Eastern Canada stations; the hard rock assumption is correct (>1500 m/s) but not as hard as often assumed (∼2000 m/s). Mean variability in VS30 is ∼400 m/s and can lead to softer rock classifications, in particular, for Paleozoic rock types with lower average rock VS near the hard/soft rock boundary. Microtremor and earthquake horizontal-to-vertical spectral ratios are obtained and provide site period classifications as an alternative to VS30.

Site Amplification Functions for Central and Eastern North America – Part II: Modular Simulation-Based Models

Site amplification models for Central and Eastern North America are developed from simulation results presented in a companion paper. Linear and nonlinear amplification functions are developed for response spectral (RS) accelerations and smoothed Fourier amplitude spectra (FAS). Linear RS model components include ground motion scaling with 30 m time-averaged shear wave velocity ( VS30 scaling) and the effects of site period and sediment depth. These models are modular and can be used with or without period or depth terms. Including these terms, especially site period, is desirable and improves model estimation. Modularity also allows linear and nonlinear amplification terms to be developed and combined with linear amplification models without bias. Nonlinear RS models reduce linear amplification as VS30 decreases and the intensity of rock outcrop motions increases. Linear FAS models are tabulated amplification values as functions of VS30 and depth; nonlinear FAS models are analogous to those for the RS. A linear model for correcting a VS30 = 760 m/s rock condition to VS = 3,000 m/s is produced.

Nonlinear Analysis of Local Site Effects on Seismic Ground Response in New Damietta City, Egypt

New Damietta City is situated in a locale of moderate notable seismicity about M6.25 have happened. These dangerous tremors started from the Mediterranean subduction zone among African and Eurasian plates and is underlain by soaked late Holocene stores. In this examination, the city of New Damietta was assessed regarding site intensification and site period. Geographical and geotechnical examination including information base of 543 boreholes were gathered from past geotechnical reports and corroborative exhausting logs were executed by the Lodging and Building national Exploration focus. These information were incorporated to decide the variety of the dirt profile and in addition the qualities of the dirt layers inside the investigation site. One dimensional ground response close examination using corresponding straight system and nonlinear procedure have been done. Nonlinear examinations' results were differentiated and those of the indistinguishable direct method, and both of the similarities and differences are discussed. It is assumed that because of nonlinearity of soil under strong ground developments, 1-D parallel direct showing overestimates the strengthening structures the extent that add up to upgrade level, and can't viably speak to full frequencies and hysteric soil lead. Along these lines, more reasonable and suitable numerical strategies for ground reaction examination ought to be reviewed