Regional attenuation models in Central and Eastern North America using the NGA-East database

2021 ◽  
pp. 875529302110187
Author(s):  
Jeff Bayless
Keyword(s):  
North America ◽  
Frequency Dependence ◽  
Gulf Coast ◽  
Site Response ◽  
Epistemic Uncertainty ◽  
Amplitude Spectrum ◽  
Active Regions ◽  
Atlantic Coastal Plain ◽  
Eastern North America ◽  
Anelastic Attenuation

The anelastic attenuation term found in ground motion prediction equations (GMPEs) represents the distance dependence of the effect of intrinsic and scattering attenuation on the wavefield as it propagates through the crust and contains the frequency-dependent quality factor, [Formula: see text], which is an inverse measure of the effective anelastic attenuation. In this work, regional estimates of [Formula: see text] in Central and Eastern North America (CENA) are developed using the NGA-East regionalization. The technique employed uses smoothed Fourier amplitude spectrum (FAS) data from well-recorded events in CENA as collected and processed by NGA-East. Regional [Formula: see text] is estimated using an assumption of average geometrical spreading applicable to the distance ranges considered. Corrections for the radiation pattern effect and for site response based on [Formula: see text] result in a small but statistically significant improvement to the residual analysis. Apparent [Formula: see text] estimates from multiple events are combined within each region to develop the regional models. Models are provided for three NGA-East regions: the Gulf Coast, Central North America, and the Appalachian Province. Consideration of the model uncertainties suggests that the latter two regions could be combined. There were not sufficient data to adequately constrain the model in the Atlantic Coastal Plain region. Tectonically stable regions are usually described by higher [Formula: see text] and weaker frequency dependence ([Formula: see text]), while active regions are typically characterized by lower [Formula: see text] and stronger frequency dependence, and the results are consistent with these expectations. Significantly different regional [Formula: see text] is found for events with data recorded in multiple regions, which supports the NGA-East regionalization. An inspection of two well-recorded events with data both in the Mississippi embayment and in southern Texas indicates that the Gulf Coast regionalization by Cramer in 2017 may be an improvement to that of NGA-East for anelastic attenuation. The [Formula: see text] models developed serve as epistemic uncertainty alternatives in CENA based on a literature review and a comparison with previously published models.

Nonlinear site amplification model for ergodic seismic hazard analysis in Central and Eastern North America

2020 ◽  
Vol 36 (1) ◽  
pp. 69-86 ◽  
Author(s):  
Youssef M. A. Hashash ◽  
Okan Ilhan ◽  
Joseph A. Harmon ◽  
Grace A. Parker ◽  
Jonathan P. Stewart ◽  
...  
Keyword(s):  
North America ◽  
Site Response ◽  
Epistemic Uncertainty ◽  
Hazard Analysis ◽  
Reference Conditions ◽  
Site Amplification ◽  
Eastern North America ◽  
Ground Acceleration ◽  
Uncertainty Model ◽  
Nonlinear Amplification

This article presents recommendations for nonlinear site amplification models in Central and Eastern North America (CENA), which are developed from one-dimensional site response analyses results and accompanies linear site amplification model in a companion article. Two median nonlinear amplification models using identical functional forms are produced as a function of VS30 and peak ground acceleration for reference conditions ( PGAr) of VS = 3000 m/s and VS30 = 760 m/s. An epistemic uncertainty model on median nonlinear amplification is proposed as a piecewise functional form to generate reasonable variations of nonlinear amplification across the period and VS30 ranges of interest. Limitations of the models are based on both the methodology of the model derivation and assumptions of nonlinear amplification model forms.

Ergodic site amplification model for central and eastern North America

2020 ◽  
Vol 36 (1) ◽  
pp. 42-68 ◽  
Author(s):  
Jonathan P. Stewart ◽  
Grace A. Parker ◽  
Gail M. Atkinson ◽  
David M. Boore ◽  
Youssef M. A. Hashash ◽  
...  
Keyword(s):  
North America ◽  
Epistemic Uncertainty ◽  
Active Regions ◽  
The United States ◽  
Site Amplification ◽  
United States Geological Survey ◽  
Eastern North America ◽  
Site Factors ◽  
Research Results ◽  
Motion Data

The United States Geological Survey national seismic hazard maps have historically been produced for a reference site condition of VS30 = 760 m/s. For other site conditions, site factors are used, which heretofore have been developed using ground motion data and simulations for shallow earthquakes in active tectonic regions. Research results from the Next Generation Attenuation–East (NGA-East) project, as well as previous and contemporaneous related research, demonstrate different levels of site amplification in central and eastern North America (CENA) as compared to active regions. We provide recommendations for modeling of ergodic site amplification in CENA based primarily on research results from the literature. The recommended model has three additive terms in natural logarithmic units. Two describe linear site amplification: an empirically constrained VS30-scaling term relative to a 760 m/s reference and a simulation-based term to adjust site amplification from the 760 m/s reference to the CENA reference of VS = 3000 m/s. The third term is a nonlinear model that is described in a companion document. All median model components are accompanied by epistemic uncertainty models.

Birds of Summer Solstice: World-Renewal Rituality on the Northern Gulf Coast of Florida

2019 ◽  
Vol 30 (2) ◽  
pp. 275-293 ◽  
Author(s):  
Joshua M. Goodwin ◽  
Kenneth E. Sassaman ◽  
Meggan E. Blessing ◽  
David W. Steadman
Keyword(s):  
North America ◽  
Gulf Coast ◽  
Fish Bone ◽  
Eastern North America ◽  
Summer Solstice ◽  
First Millennium ◽  
Northern Gulf Coast

Prevalent as bird imagery is in the ritual traditions of eastern North America, the bony remains of birds are relatively sparse in archaeological deposits and when present are typically viewed as subsistence remains. A first-millennium ad civic-ceremonial centre on the northern Gulf Coast of Florida contains large pits with bird bones amid abundant fish bone and other taxa. The avian remains are dominated by elements of juvenile white ibises, birds that were taken from offshore rookeries at the time of summer solstices. The pits into which they were deposited were emplaced on a relict dune with solstice orientations. The timing and siting of solstice feasts at this particular centre invites discussion of world-renewal rituality and the significance of birds in not only the timing of these events but also possibly as agents of balance and rejuvenation.

Significance of site natural period effects for linear site amplification in central and eastern North America: Empirical and simulation-based models

2020 ◽  
Vol 36 (1) ◽  
pp. 87-110 ◽  
Author(s):  
Youssef M. A. Hashash ◽  
Okan Ilhan ◽  
Behzad Hassani ◽  
Gail M. Atkinson ◽  
Joseph Harmon ◽  
...  
Keyword(s):  
North America ◽  
Site Response ◽  
Reference Conditions ◽  
Site Amplification ◽  
Empirical Models ◽  
Response Analysis ◽  
Eastern North America ◽  
Natural Period ◽  
Motion Models ◽  
Simulation Based

This article evaluates linear simulation-based and empirical site amplification models including site natural period dependency parameters to account for the distinctive amplification behavior near site fundamental frequencies resulting from the sharp impedance contrast between soil and underlying hard bedrock in central and eastern North America (CENA). The simulation-based amplification models are developed using 581,685 frequency-domain linear analyses generated from a parametric study and include VS30-scaling and site natural period ( Tnat) parameters. The empirical models are derived from residuals analyses of ground-motion models for two reference conditions: B/C boundary ( VS30 = 760 m/s) and CENA hard-rock condition ( VS = 3000 m/s). The simulation-based and empirical models are compared for 8 site profiles in CENA to measured horizontal-to-vertical (H/V) component response spectral (RS) ratios, the mean of linear simulations for similar sites, and one-dimensional (1D) linear site response analysis for four of these sites. Comparisons between observed and estimated site amplification behaviors highlight model dependency on Tnat in CENA. Model consistencies and differences related to the distinct linear amplification features near site fundamental frequency are discussed.

Empirical Linear Seismic Site Amplification in Central and Eastern North America

2019 ◽  
Vol 35 (2) ◽  
pp. 849-881 ◽  
Author(s):  
Grace A. Parker ◽  
Jonathan P. Stewart ◽  
Youssef M. A. Hashash ◽  
Ellen M. Rathje ◽  
Kenneth W. Campbell ◽  
...  
Keyword(s):  
North America ◽  
Ground Motion ◽  
Site Response ◽  
Site Amplification ◽  
Eastern North America ◽  
Resonance Effects ◽  
Bayesian Techniques ◽  
Motion Data ◽  
Motion Models ◽  
Scaling Models

We present empirical linear site amplification models conditioned on time-averaged shear wave velocity in the upper 30 m ( VS30) for central and eastern North America. The models are derived from ground motion data and site condition information from the NGA-East project and are intended for use with reference rock ground motion models. Site amplification is found to scale with VS30 for intermediate to stiff site conditions ( VS30 > 300 m/s) in a weaker manner than for active tectonic regions such as the western United States. For stiff sites ( >800 m/s), we find differences in site amplification for previously glaciated and nonglaciated regions, with nonglaciated sites having lower amplification. The models were developed using a combination of least-squares, mixed effects, and Bayesian techniques; the latter show that accounting for predictor uncertainty does not appreciably affect the median model but decreases model dispersion. Our VS30-scaling models are modular and additive to simulation-based models for the nonlinear components of site response. A limitation of the present models is that they do not account for site-specific resonance effects.

Evidence for Stepped Pyramids of Shell in the Woodland Period of Eastern North America

2016 ◽  
Vol 81 (2) ◽  
pp. 345-363 ◽  
Author(s):  
Thomas J. Pluckhahn ◽  
Victor D. Thompson ◽  
W. Jack Rink
Keyword(s):  
North America ◽  
Gulf Coast ◽  
Construction Material ◽  
Time Frame ◽  
Late Woodland ◽  
Woodland Period ◽  
Alternative Form ◽  
Eastern North America ◽  
Late Woodland Period ◽  
Mississippian Period

AbstractAntiquarians of the nineteenth century referred to the largest monumental constructions in eastern North America as pyramids, but this usage faded among archaeologists by the mid-twentieth century. Pauketat (2007) has reintroduced the term pyramid to describe the larger, Mississippian-period (A.D. 1050 to 1550) mounds of the interior of the continent, recognizing recent studies that demonstrate the complexity of their construction. Such recognition is lacking for earlier mounds and for those constructed of shell. We describe the recent identification of stepped pyramids of shell from the Roberts Island Complex, located on the central Gulf Coast of Florida and dating to the terminal Late Woodland period, A.D. 800 to 1050, thus recognizing the sophistication of monument construction in an earlier time frame, using a different construction material, and taking an alternative form.

scholarly journals Trace fossils on dinosaur bones reveal ecosystem dynamics along the coast of eastern North America during the latest Cretaceous

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e4973
Author(s):  
Chase D. Brownstein
Keyword(s):  
North America ◽  
Marine Invertebrates ◽  
Atlantic Coastal Plain ◽  
Ecosystem Dynamics ◽  
Eastern North America ◽  
Marine Deposits ◽  
Terrestrial Vertebrate ◽  
Atlantic Coastal ◽  
Tibia Shaft

Direct evidence of paleoecological processes is often rare when the fossil record is poor, as in the case of the Cretaceous of eastern North America. Here, I describe a femur and partial tibia shaft assignable to theropods from two Late Cretaceous sites in New Jersey. The former, identifiable as the femur of a large ornithomimosaur, bears several scores interpreted as shark feeding traces. The tibia shaft has punctures and flaked bone from the bites of mid-sized crocodyliforms, the first documented occurrence of crocodyliform traces on dinosaur bone from the Maastrichtian of the Atlantic Coastal Plain. The surface of the partial tibia is also littered with indentations interpreted as the traces of invertebrates, revealing a microcosm of biological interaction on the coastal seafloor of the Cretaceous Atlantic Ocean. Massive crocodyliforms, such as Deinosuchus rugosus and the slightly smaller Deltasuchus motherali, maintained the role of terrestrial vertebrate taphonomic process drivers in eastern North America during the Cretaceous. The report of crocodyliform bite marks on the ornithomimosaur tibia shaft in this manuscript reinforces the importance of the role of crocodyliforms in the modification of terrestrial vertebrate remains during the Cretaceous in North America. The preserved invertebrate traces add to the sparse record of the presence of barnacles and other marine invertebrates on dinosaur bone, and the evidence of shark feeding on the ornithomimosaur femur support the “bloat-and-float” model of terrestrial vertebrate fossil deposition in marine deposits from the Cretaceous of eastern North America.

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