Search USGS⌕ Search
Home/Archive/USGS

USGS · 70228362

NGA-subduction global ground motion models with regional adjustment factors

Grace Alexandra Parker·Jonathan P. Stewart·David M. Boore·Gail M. Atkinson·Behzad Hassani
View original source ↗Export metadata ↓

Abstract

We develop semi-empirical ground motion models (GMMs) for peak ground acceleration, peak ground velocity, and 5%-damped pseudo-spectral accelerations for periods from 0.01 to 10 s, for the median orientation-independent horizontal component of subduction earthquake ground motion. The GMMs are applicable to interface and intraslab subduction earthquakes in Japan, Taiwan, Mexico, Central America, South America, Alaska, the Aleutian Islands, and Cascadia. The GMMs are developed using a combination of data inspection, data regression with respect to physics-informed functions, ground-motion simulations, and geometrical constraints for certain model components. The GMMs capture observed differences in source and path effects for interface and intraslab events, conditioned on moment magnitude, rupture distance, and hypocentral depth. Site effect and aleatory variability models are shared between event types. Regionalized GMM components include the model constant (that controls ground motion amplitude), anelastic attenuation, magnitude-scaling break point, linear site response, and sediment depth terms. We develop models for the aleatory between-event variability ( τ ) "> ( τ ) , within-event variability ( ϕ ) "> ( ϕ ) , single-station within-event variability ( ϕ SS ) "> ( ϕ SS ) , and site-to-site variability ( ϕ S 2 S ) "> ( ϕ S 2 S ) . Ergodic analyses should use the median GMM and aleatory variability computed using the between-event and within-event variability models. An analysis incorporating non-ergodic site response should use the median GMM at the reference shear-wave velocity condition, a site-specific site response model, and aleatory variability computed using the between-event and single-station within-event variability models. Epistemic uncertainty in the median model is represented by standard deviations on the regional model constants, which facilitates scaled-backbone representations of model uncertainty in hazard analyses.

Explore related subjects

Earthquake SpectraArticle

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Grace Alexandra Parker, Jonathan P. Stewart, David M. Boore, Gail M. Atkinson, Behzad Hassani. 2021-08-13. NGA-subduction global ground motion models with regional adjustment factors. https://doi.org/10.1177/87552930211034889

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

An examination of the reasons for, and variability of, the differences between response spectra and pseudo response spectra

For many decades, it has been common practice to overlook the differences between response spectra and pseudo response spectra. This practice stems from analyses indicating that the average difference between response spectra and pseudo response spectra is negligible for a viscous damping ratio of 5%, which is near-universally adopted. As others have shown, the differences depend strongly on the damping ratio, earthquake magnitude, and oscillator period, with larger differences for larger damping, smaller magnitudes, and longer periods. To quantify the full statistical distribution of the ratio of the absolute acceleration response spectrum (SA) to the pseudo absolute acceleration response spectrum (PSA), we fit empirical ratios with the generalized gamma distribution. Data for magnitudes from 4.0 to 5.5 give 95% prediction intervals for the ratio of 1.00–1.02 at 1 s and 1.01–2.24 at 10 s for 5% damping. For 30% damping, these intervals increase to 1.14–2.01 at 1 s and 1.62–11.8 at 10 s, respectively. Further, we demonstrate how the shape of the ground-motion Fourier amplitude spectrum interacts with the natural period of the oscillator to control the differences in the response spectra type. Routinely treating the two measures of acceleration response spectra as interchangeable may lead to unacceptable inconsistencies when the response spectra of individual records are important or when larger damping ratios are used, such as in direct displacement-based design. If one must convert between them, the uncertainty of the conversion should be accounted for during analysis.

Earthquake Spectra↗
USGS2026

Accounting for biases in the analysis of building damage data for the 2023 M7.8 Türkiye/Syria earthquake sequence

In the aftermath of a large earthquake, several practical constraints affect the systematic collection of data for assessing building damage. The available data are therefore typically incomplete, frequently missing key information such as the type of construction, age and geographic location. Moreover, the observations often favour certain locations and damage grades. In the absence of robust methods, using such data directly for characterising the building stock or conducting fragility assessments can introduce systematic bias. Using the 2023 M7.8 Türkiye/Syria earthquake sequence as a case study, we propose a statistical model that enables joint inference over the inventory and fragility of the building stock while explicitly accounting for sources of data error and missing information. The results show higher-than-expected vulnerability amongst several building types, particularly mid- and high-rise reinforced concrete buildings, which performed extremely poorly during the 2023 earthquake sequence. The proposed Bayesian framework provides rigorous uncertainty quantification that can be propagated to future applications.

Earthquake Spectra↗
USGS2026

Suite of regional seismic velocity models for the U.S. Atlantic and Gulf Coastal Plains (CPVMv2.0): Incorporating epistemic uncertainty in velocity models

The U.S. Atlantic and Gulf Coastal Plain (CP) sediments are kilometers-thick, low-velocity deposits underlain by high-velocity bedrock that create regional patterns of amplification and attenuation of ground motions. Capturing these effects is challenging because of the limited subsurface information available, particularly the shear wave velocity ( V S ) structure down to bedrock (or assumed reference rock condition) and the associated uncertainties. This paper introduces a new suite of regional velocity models for the CPs, called CPVMv2.0, which builds upon previous efforts integrating geology, V S measurements, and sediment thickness in the region. CPVMv2.0 uses 750 measured V S profiles and identifies nine surficial-geologic-age-based and geography-based groups (with alternative physiographic-province-based subgroupings) to create surface-based median V S profiles. This suite of new models also includes six subsurface-based median profiles developed using geologic age boundaries from depth-dependent stratigraphic sequences extracted from the U.S. Geological Survey National Crustal Model. In addition to quantifying aleatory variability in sediment velocity, weathered-rock velocity, bedrock velocity, and the depth to the top of weathered rock and bedrock, CPVMv2.0 provides alternative profile models that allow for the characterization of the epistemic uncertainty. This is a unique and relevant feature of CPVMv2.0. Our suite of models was validated using measured and estimated fundamental resonant frequencies as well as other V S models in the region. CPVMv2.0 enables the incorporation of crustal velocities (and their associated variability and uncertainty) into physics-based ground-motion simulations in the eastern United States and into the development of new ground-motion models aiming to characterize systematic site effects via V S30 , depths to V S isosurfaces, and/or sediment thickness in the region.

U.S. Atlantic and Gulf Coastal Plains↗