Summary of the Abrahamson & Silva NGA Ground‐Motion Relations

Abstract

Empirical ground‐motion models for the rotation‐independent average horizontal component from shallow crustal earthquakes are derived using the PEER NGA database. The model is applicable to magnitudes 5–8.5, distances 0–200 km , and spectral periods of 0–10 sec . In place of generic site categories (soil and rock), the site is parameterized by average shear‐wave velocity in the top 30 m (V S 30 ) and the depth to engineering rock (depth to V S =1000 m/s). In addition to magnitude and style‐of‐faulting, the source term is also dependent on the depth to top‐of‐rupture: for the same magnitude and rupture distance, buried ruptures lead to larger short‐period ground motions than surface ruptures. The hanging‐wall effect is included with an improved model that varies smoothly as a function of the source properties (M, dip, depth), and the site location. The standard deviation is magnitude dependent with smaller magnitudes leading to larger standard deviations. The short‐period standard deviation model for soil sites is also distant‐dependent due to nonlinear site response, with smaller standard deviations at short distances.