Calibration of the U.S. Geological Survey National Crustal Model

Relatively little research has been conducted to systematically quantify the nationwide earthquake risk of gas pipelines in the US; simultaneously, national guidance is limited for operators across the country to consistently evaluate the earthquake risk of their assets. Furthermore, many challenges and uncertainties exist in a comprehensive seismic risk assessment of gas pipelines. As a first stage in a systematic nationwide assessment, we quantify the earthquake risk of gas transmission pipelines in the conterminous US due to strong ground shaking, including the associated uncertainties. Specifically, we integrate the US Geological Survey 2018 National Seismic Hazard Model, a logic tree-based exposure model, three different vulnerability models, and a consequence model. The results enable comparison against other risk assessment efforts, encourage more transparent deliberation regarding alternative approaches, and facilitate decisions on potentially assessing localized risks due to ground failures that require site-specific data. Based on the uncertainties approximated herein, the resulting sensitivity analyses suggest that the vulnerability model is the most influential source of uncertainty. Finally, we highlight research needs such as (1) developing more vulnerability models for regional seismic risk assessment of gas pipelines; (2) identifying, prioritizing, and measuring input pipeline attributes that are important for estimating seismic damage; and (3) better quantifying seismic hazards with their uncertainties at the national scale, for both ground failures and ground shaking.

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“…• USGS 2020 National Crustal Model (Boyd 2020), publicly available at https://doi.org/10.5066/P9GO3CP8.…”

Section: Appendix Results For Additional Damage Modelsmentioning

confidence: 99%

Earthquake Risk of Gas Pipelines in the Conterminous United States and Its Sources of Uncertainty

Kwong

Jaiswal

Baker

et al. 2022

ASCE-ASME J. Risk Uncertainty Eng. Syst., Part A: Civ. Eng.

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“…Our V S model is developed using surface geology and near-surface geotechnical data, but it does not have lithology-based subgeologic groups as used by Thompson et al (2014), Parker et al (2017), and Ahdi et al (2017) because of the lack of more detailed descriptions of the stratigraphic sequences across the CP region. Future developments of this model could also use lithology information from the geologic framework in the U.S. Geological Survey National Crustal Model (Boyd, 2020).…”

Section: Vs Profile Development Overviewmentioning

confidence: 99%

Regional seismic velocity model for the U.S. Atlantic and Gulf Coastal Plains based on measured shear wave velocity, sediment thickness, and surface geology

Gann-Phillips,

Cabas,

et al. 2024

Earthquake Spectra

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The Atlantic and Gulf Coastal Plains (CPs) are characterized by widespread accumulations of low-velocity sediments and sedimentary rock that overlay high-velocity bedrock. Geology and sediment thickness greatly influence seismic wave propagation, but current regional ground motion amplification and seismic hazard models include limited characterization of these site conditions. In this study, a new regional seismic velocity model for the CPs is created by integrating shear wave velocity (VS) measurements, surface geology, and a sediment thickness model recently developed for the CPs. A reference rock VS of 3000 m/s has been assumed at the bottom of the sedimentary columns, which corresponds to the base of Cretaceous and Mesozoic sediments underlying the Atlantic CP and the Gulf CP, respectively. Measured VS profiles located throughout the CPs are sorted into five geologic groups of varying age, and median VS profiles are developed for each group by combining measured VS values within layer thicknesses defined by an assumed layering ratio. Statistical analyses are also conducted to test the appropriateness of the selected groups. A power law model with geology-informed coefficients is used to extend the median velocity models beyond the depths where measured data were available. The median VS profiles provide reasonable agreement with other generic models applicable for the region, but they also incorporate new information that enables more advanced characterizations of site response at regional scales and their effective incorporation into seismic hazard models and building codes. The proposed median velocity profiles can be assigned within a grid-based model of the CPs according to the spatial distribution of geologic units at the surface.

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Spectral Inversion for Seismic Site Response in Central Oklahoma: Low-Frequency Resonances from the Great Unconformity

Moschetti

Hartzell

2020

Bulletin of the Seismological Society of America

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We investigate seismic site response by inverting seismic ground-motion spectra for site and source spectral properties, in a region of central Oklahoma, where previous ground-motion studies have indicated discrepancies between observations and ground-motion models (GMMs). The inversion is constrained by a source spectral model, which we computed from regional seismic records, using aftershocks as empirical Green’s functions to deconvolve site and path effects. Site spectra across the region exhibit multiple, strong, low-frequency (f<2 Hz) resonances. Modeling of vertically propagating SH waves reproduces the mean amplitudes and frequencies of the site spectra and requires a deep (∼1–2 km) impedance contrast. Comparison of regional seismic velocity models and geologic profiles indicates that the seismic impedance contrast is, or is in proximity to, the Great Unconformity, which marks the interface between Precambrian basement rocks and overlying Paleozoic sedimentary rocks. Depth to Precambrian basement increases to the southwest across the study region (∼1500–4500 m), and the fundamental frequencies of the site spectra are anticorrelated with basement depth. The first higher-mode resonance also exhibits dependence on basement depth; although modeling suggests that the second higher mode should depend on basement depth, site spectra do not support this. The low-frequency resonances in central Oklahoma are not represented in the GMMs used in current seismic hazard analyses for tectonic earthquakes, though approaches to account for such features are under consideration in other regions of the central and eastern United States. Given the broad spatial extent of the Great Unconformity underlying eastern North America, it is likely that similar effects on seismic site response also occur in other areas. This study highlights the impact of regional geologic structure on earthquake ground motions and reiterates the need for modeling regional effects to improve ground-motion predictions and seismic hazard assessments.

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Calibration of the U.S. Geological Survey National Crustal Model

Cited by 7 publications

References 14 publications

Earthquake Risk of Gas Pipelines in the Conterminous United States and Its Sources of Uncertainty

Earthquake Risk of Gas Pipelines in the Conterminous United States and Its Sources of Uncertainty

Regional seismic velocity model for the U.S. Atlantic and Gulf Coastal Plains based on measured shear wave velocity, sediment thickness, and surface geology

Spectral Inversion for Seismic Site Response in Central Oklahoma: Low-Frequency Resonances from the Great Unconformity

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