Characterizing and Imaging Sedimentary Strata Using Depth‐Converted Spectral Ratios: An Example from the Atlantic Coastal Plain of the Eastern United States

2018 ◽  
Vol 108 (5A) ◽  
pp. 2801-2815 ◽  
Author(s):  
Thomas L. Pratt
Keyword(s):  
United States ◽  
Coastal Plain ◽  
Atlantic Coastal Plain ◽  
Eastern United States ◽  
Spectral Ratios ◽  
Atlantic Coastal

scholarly journals Fate of the other redcoat: remnants of colonial British foxes in the eastern United States

2015 ◽  
Vol 97 (1) ◽  
pp. 298-309 ◽  
Author(s):  
Adrienne E. Kasprowicz ◽  
Mark J. Statham ◽  
Benjamin N. Sacks
Keyword(s):  
United States ◽  
Coastal Plain ◽  
Red Fox ◽  
Hudson River ◽  
Atlantic Coastal Plain ◽  
Population Increase ◽  
Eastern United States ◽  
Red Foxes ◽  
Atlantic Coastal ◽  
Natural Population Increase

Abstract Red foxes were absent or rare in the southeastern United States until the late 1800s. Their origins potentially include natural population increase/expansion, translocations from Europe, and, eventually, 20th century fur farming. Previous studies have found no European haplotypes in North America, but few samples were sourced from the Atlantic coastal plain, closer to the source of putative introductions. Through analysis of mitochondrial DNA in 584 red foxes from this region, we identified indigenous haplotypes in ≥ 35% of foxes, 1 of 2 European haplotypes in 17% of foxes and fur farm haplotypes in ≥ 13% of foxes; another 35% of foxes had haplotypes potentially indigenous or native. In contrast, only 3 of 135 (2%) male foxes carried a single European Y chromosome haplotype. Most European and fur farm haplotypes were found near the densely human-populated coastal plain and Hudson River lowlands; most red foxes of the Appalachians and Piedmont had native eastern haplotypes. Our findings suggest that the more remote, upland populations primarily reflect indigenous red fox matrilines, whereas urban-associated populations in and around the mid-Atlantic coastal plain and Hudson lowlands reflect an admixture of native and nonnative maternal sources. Autosomal markers are needed to further elucidate the extent of European and fur farm introgression in the Appalachians and further west.

Three forgotten earthquakes

1963 ◽  
Vol 53 (3) ◽  
pp. 687-692
Author(s):  
Gerald R. MacCarthy
Keyword(s):  
United States ◽  
New York ◽  
North Carolina ◽  
South Carolina ◽  
Coastal Plain ◽  
Maximum Intensity ◽  
Atlantic Coastal Plain ◽  
Eastern United States ◽  
Atlantic Coastal

Abstract For a given maximum intensity, most earthquakes of the Eastern United States are felt over much wider area than their western counterparts. Several of these eastern shocks, have, because of their relatively low maximum intensities, received little or no attention in seismological literature. Three such earthquakes will be described in terms of contemporary accounts: those of March 9, 1828, April 29, 1852, and of August 31, 1861. In no case did the maximum intensity exceed about VI on the Mercalli Scale, yet each was felt over many thousands of square miles. The 1828 shock affected at least 190,000 square miles, and was reported from Pennsylvania to South Carolina. That of 1852 affected about 187,000 square miles, and was reported from New York to North Carolina. That of 1861 affected at least 280,000 square miles, and was reported from Maryland to the Georgia-Alabama border. All three were felt from the Atlantic Coastal Plain westward into Ohio.

Characterizing Fundamental Resonance Peaks on Flat-Lying Sediments Using Multiple Spectral Ratio Methods: An Example from the Atlantic Coastal Plain, Eastern United States

2021 ◽  
Author(s):  
Lisa S. Schleicher ◽  
Thomas L. Pratt
Keyword(s):  
United States ◽  
Coastal Plain ◽  
Site Response ◽  
Spectral Ratio ◽  
Atlantic Coastal Plain ◽  
Unconsolidated Sediments ◽  
Eastern United States ◽  
Fundamental Resonance ◽  
Hvsr Method ◽  
Atlantic Coastal

ABSTRACT Damaging ground motions from the 2011 Mw 5.8 Virginia earthquake were likely increased due to site amplification from the unconsolidated sediments of the Atlantic Coastal Plain (ACP), highlighting the need to understand site response on these widespread strata along the coastal regions of the eastern United States. The horizontal-to-vertical spectral ratio (HVSR) method, using either earthquake signals or ambient noise as input, offers an appealing method for measuring site response on laterally extensive sediments, because it requires a single seismometer rather than requiring a nearby bedrock site to compute a horizontal sediment-to-bedrock spectral ratio (SBSR). Although previous studies show mixed results when comparing the two methods, the majority of these studies investigated site responses in confined sedimentary basins that can generate substantial 3D effects or have relatively small reflection coefficients at their base. In contrast, the flat-lying ACP strata and the underlying bedrock reflector should cause 1D resonance effects to dominate site response, with amplification of the fundamental resonance peaks controlled by the strong impedance contrast between the base of the sediments and the underlying bedrock. We compare site-response estimates on the ACP strata derived using the HVSR and SBSR methods from teleseismic signals recorded by regional arrays and observe a close match in the frequencies of the fundamental resonance peak (f0) determined by both methods. We find that correcting the HVSR amplitude using source term information from a bedrock site and multiplying the peak by a factor of 1.2 results in amplitude peaks that, on average, match SBSR results within a factor of 2. We therefore conclude that the HVSR method may successfully estimate regional linear weak-motion site-response amplifications from the ACP, or similar geologic environments, when appropriate region-specific corrections to the amplitude ratios are used.

Constraining Properties of Sedimentary Strata Using Receiver Functions: An Example from the Atlantic Coastal Plain of the Southeastern United States

2020 ◽  
Vol 110 (2) ◽  
pp. 519-533 ◽  
Author(s):  
Erin Cunningham ◽  
Vedran Lekic
Keyword(s):  
United States ◽  
Coastal Plain ◽  
Velocity Profiles ◽  
Receiver Functions ◽  
Atlantic Coastal Plain ◽  
P Wave ◽  
Seismic Velocities ◽  
Eastern United States ◽  
Converted Wave ◽  
Atlantic Coastal

ABSTRACT Thickness and seismic velocities of sedimentary sequences strongly affect their response during earthquakes, which can prolong and amplify ground motions. We characterize shallow structure of Atlantic Coastal Plain (ACP) sediments using a passive-seismic approach based on high-frequency P-to-S receiver functions. We map the site-specific fundamental frequency for 64 USArray Transportable Array stations and confirm that the method yields results similar to those from traditional spectral ratio techniques, with fundamental frequencies between 0.1 and 1 Hz. In addition, using sediment S-wave reverberations and P-to-S phase arrival times measured directly from the receiver functions, we invert for average S- and P-wave velocity profiles of the ACP sedimentary strata. We find that VS increases with depth following a power-law relationship (VS∝z) whereas the increase of VP with depth is more difficult to constrain using converted wave methods; therefore, we choose to use the Brocher (2005) relationship to obtain VP through a VP/VS relationship. Finally, we use the variation of measured S-reverberation amplitudes with depth to validate these velocity profiles. These results have implications for seismic shaking across the ACP, which covers large portions of the eastern United States.

Carabodes of the eastern United States and adjacent Canada (Acari: Oribatida: Carabodidae)

1992 ◽  
Vol 70 (10) ◽  
pp. 2042-2058 ◽  
Author(s):  
R. Marcel Reeves
Keyword(s):  
United States ◽  
North America ◽  
Coastal Plain ◽  
Forest Floor ◽  
Appalachian Mountains ◽  
Atlantic Coastal Plain ◽  
Eastern North America ◽  
Eastern United States ◽  
Thelytokous Parthenogenesis ◽  
Atlantic Coastal

Adults of four new species of Carabodes, C. chandleri, C. erectus, C. interruptus, and C. pentasetosus, and the immatures of C. erectus, are described. All have been collected from a variety of forest-floor habitats, with C. chandleri, C. interruptus, and C. pentasetosus more common in leaf litter, and C. erectus preferring polyporous fungi. All four species are widely distributed in eastern North America, with C. chandleri, C. erectus, and C. interruptus more abundant in samples from the Appalachian Mountains and C. pentasetosus in those from the Atlantic coastal plain. Thelytokous parthenogenesis is suspected to occur in C. pentasetosus n.sp. and Carabodes granulatus Banks. A key to the 19 species of Carabodes found in North America is provided.

Past permafrost on the Mid-Atlantic Coastal Plain, eastern United States

2009 ◽  
Vol 20 (3) ◽  
pp. 285-294 ◽  
Author(s):  
Hugh French ◽  
Mark Demitroff ◽  
Wayne L. Newell
Keyword(s):  
United States ◽  
Coastal Plain ◽  
Atlantic Coastal Plain ◽  
Eastern United States ◽  
Atlantic Coastal

Characterizing Ground-Motion Amplification by Extensive Flat-Lying Sediments: The Seismic Response of the Eastern U.S. Atlantic Coastal Plain Strata

2021 ◽  
Author(s):  
Thomas L. Pratt ◽  
Lisa S. Schleicher
Keyword(s):  
United States ◽  
Coastal Plain ◽  
Fourier Transforms ◽  
Resonance Peak ◽  
Atlantic Coastal Plain ◽  
Eastern United States ◽  
Sedimentary Sequences ◽  
The North ◽  
Basement Rocks ◽  
Atlantic Coastal

ABSTRACT We examine the effects that Atlantic Coastal Plain (ACP) strata have on ground motions in the eastern and southeastern United States. The ACP strata consist of widespread, nearly flat-lying sediments, the upper portions of which are unconsolidated or semiconsolidated. The ACP sediments are deposited primarily on crystalline basement rocks, creating large velocity and density contrasts with the underlying rocks. At 211 sites on ACP strata to thicknesses of 4000 m, we compute spectral ratios relative to the average of four bedrock sites west or northwest of the strata. Sites consist of stations of Earthscope’s USArray Transportable Array (TA), and temporary deployments in the Southeast Suture of the Atlantic Margin Experiment (SESAME), Eastern North American Margin (ENAM) experiment, and the DCShake deployment in Washington, D.C. For the TA and SESAME stations, we use signals from 13 teleseisms and three regional earthquakes as input, combining the north and east components of motion after taking the Fourier transforms. We also include similarly processed site responses from the ENAM and DCShake arrays that were computed in earlier studies. Results show prominent, fundamental resonance peaks at frequencies determined by reverberations in the entire sediment column, and that often define the largest amplifications for each frequency. As frequencies increase, these resonance peaks migrate to thinner ACP strata and increase in amplitude. The peaks are well defined at frequencies below about 1 Hz, but become narrower and less defined regionally at higher frequencies. We develop simple equations to characterize amplification versus ACP thickness, which we approximate by cosine and Gaussian curves with amplifications of 1 on bedrock and rising to the resonance peak, and then decreasing to an average amplification at thicknesses greater than twice the resonance peak. Comparisons with other site corrections for the central and eastern United States based on sediment thickness show similarities on thin ACP strata but divergence on thicker sediments. The results also demonstrate the effectiveness of using teleseismic arrivals to characterize the site responses of sedimentary sequences.

Sign in / Sign up

Export Citation Format

Share Document