Alternative (G‐16v2) Ground‐Motion Prediction Equations for Central and Eastern North America

Abstract

This article introduces new ground‐motion prediction equations (GMPE) for central and eastern North America that represents an alternative, more physically justified approach to ground‐motion attenuation modeling than my previous Graizer (2016) G‐16 model. The new model has a bilinear slope of ∼ R −1 within 70 km from the fault (confirmed by empirical data) with a slope of ∼ R −0.5 at larger distances corresponding to the geometrical spreading of body and surface waves. This new (G‐16v2) model is based on the Next Generation Attenuation (NGA)‐East database for the horizontal peak ground acceleration and 5% damped pseudospectral acceleration RotD50 component (Goulet et al. , 2014) and also on comparisons with western United States data and ground‐motion simulations. Based on data, I estimated the average slope of the distance attenuation within the 50–70 km distance from the fault to be ∼−1.0 at most of the frequencies supporting regular geometrical spreading of body waves. Multiple inversions are performed to estimate apparent (combination of intrinsic and scattering) attenuation of response spectral acceleration (SA) amplitudes from the NGA‐East database for incorporation into the GMPE. These estimates demonstrate a difference between classical seismological Q ( f ) and the above‐mentioned attenuation factor that I recommend calling Q SA( f ). Based on residuals, I adjusted previously developed site correction (Graizer, 2016) that was based on multiple runs of representative V S 30 (time‐averaged shear‐wave velocity in the upper 30 m of the geological material) profiles through SHAKE‐type equivalent‐linear codes. Site amplifications are calculated relative to the hard‐rock definition used in nuclear industry ( V S =2800 m/s). These improvements resulted in a modest reduction in total ( σ ) and within‐event (![Graphic][1] ) logarithmic standard deviations in the new G‐16v2 relative to G‐16 model. The number of model predictors is limited to a few measurable parameters: moment magnitude M , closest distance to fault rupture plane R rup, V S 30, and apparent attenuation factor Q SA( f ). The model is applicable for the stable continental regions and covers the following range: 4.0≤ M ≤8.5, 0≤ R rup≤1000 km, 450≤ V S 30≤2800 m/s, and frequencies 0.1≤ f ≤100 Hz. [1]: /embed/inline-graphic-1.gif