NGA-East Ground-Motion Characterization model part I: Summary of products and model development

Abstract

In this article, we present an overview of the research project NGA-East, Next Generation Attenuation for Central and Eastern North America (CENA), and summarize the key methodology and products. The project was tasked with developing a new ground motion characterization (GMC) model for CENA. The final NGA-East GMC model includes a set of 17 median ground motion models (GMMs) for peak ground acceleration and velocity (PGA, PGV) and response spectral ordinates for periods ranging from 0.01 to 10 s. The NGA-East GMMs are applicable to horizontal components of ground motions on very hard rock, for the moment magnitude range of 4.0–8.2, and distances of up to 1500 km. The aleatory standard deviations of GMMs are also provided for site-specific analysis (single-station standard deviation) and for general probabilistic seismic hazard analyses (PSHA) applications (ergodic standard deviation). In addition, adjustment factors are provided for source depth and hanging-wall effects, as well as for hazard computations at sites in the Gulf Coast Region. During the course of the project, several innovative technologies were developed and implemented to increase the transparency and repeatability of the GMC building process. This involved expanding on a set of candidate median GMMs to define and capture an appropriate range of epistemic uncertainty in ground motions. We also developed a new approach for modeling the aleatory variability that was completely independent of the median GMMs. The development made extensive use of the CENA database but also borrowed data from other parts of the world when relevant and led to an integrated suite of models. Through this repeatable process, epistemic uncertainty could be quantified more objectively than before, relying less on expert opinion. The NGA-East project went through a comprehensive Seismic Senior Hazard Analysis Committee (SSHAC) Level 3 peer review process before its release.

Ground-motion model for the standardized version of cumulative absolute velocity

“…In 2011, the authors developed a ground-motion model (GMM) for a damage-related version of cumulative absolute velocity ( CAV ) used by the US Nuclear Regulatory Agency (USNRC, 1997) to evaluate whether a US nuclear power plant must be shut down for inspection after an earthquake (Campbell and Bozorgnia, 2011; hereafter CB11). The GMM was developed using the database compiled for the Next Generation Attenuation (NGA) project (Power et al, 2008), currently referred to as NGA-West1 to distinguish it from subsequent NGA projects for western North America and other active tectonic regions (NGA-West2; Bozorgnia et al, 2014), central and eastern North America and other stable tectonic regions (NGA-East; Goulet et al, 2021), and global subduction zones (NGA-Subduction; Bozorgnia et al, 2022). The database is described in detail in Chiou et al (2008).…”

Exploring Australian hazard map exceedance using an Atlas of historical ShakeMaps

“…This first analysis uses GMMs preferred for use for Australian crustal conditions (Allen et al, 2019). Second, an alternative composite map is produced using the mean next-generation attenuation (NGA)-East GMM (Goulet et al, 2017(Goulet et al, , 2021-developed for Central and Eastern North America (CENA)with a 0.50 weight, and maintains the four preferred GMMs at a weight of 0.125 each (Table 1; Figure 4b). The latter GMM logic tree represents a more conservative scenario given the propensity of these CENA GMMs to overestimate short-period ground motions for Australian earthquakes (Ghasemi and Allen, 2018;Hoult et al, 2021a;Miller et al, 2023), particularly in the far-field (Allen and Atkinson, 2007).…”

Bayesian analysis of ground motion models using chimney fragility curves: 2021, 5.9-Mw Woods Point intraplate earthquake, Victoria, Australia

“…GMMs are used in this study, on the basis that they were used in the Australian NSHA18, previously a part of it, or being considered to be a candidate GMM. They include Allen (2012), Atkinson & Boore (2006), Boore et al (2014), Chiou & Youngs SWISS1 (2008), Chiou & Youngs (2014), Somerville et al non-cratonic (2009), Somerville et al Yilgarn Craton (2009), Gaull et al South East Australia (1990), Gaull et al WA (1990), and NGA-E (Goulet et al, 2021). GMMs currently contributing to the NSHA18 can be seen in Table 1 with their respective expert elicitation weights.…”

“…Future editions of the NSHA are considering the adaption of the Next Generation Attenuation for Central and Eastern North America (NGA-East (Goulet et al, 2021)) as a GMM candidate.…”