Thin lithosphere beneath the central Appalachian Mountains: Constraints from seismic attenuation beneath the MAGIC array

Byrnes, J. S.; Bezada, Maximiliano; Long, Maureen D.; Benoit, M. H.

doi:10.1016/j.epsl.2019.04.045

Cited by 31 publications

(130 citation statements)

References 69 publications

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“…Our temperature results strongly imply that there is no evidence of melt in the uppermost mantle of the CEUS because the highest temperature is less than the adiabatic temperature. This is what we would expect to see given the lack of active volcanism in the CEUS; other studies (e.g., Byrnes et al, ; Evans et al, ) suggest partial melt in the upper mantle at depth 120 to 200 km beneath the central Appalachian Mountains, where the lithosphere has thinned to 80 km.…”

Section: Temperature Implicationssupporting

confidence: 71%

Seismic Attenuation and Velocity Measurements of the Uppermost Mantle Beneath the Central and Eastern United States and Implications for the Temperature of the North American Lithosphere

2020

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We constructed a detailed map of the uppermost mantle seismic structure beneath the Central and Eastern United States (CEUS) using the International Seismological Centre Bulletin and seismic waveforms from USArray. Identical Pn and Sn travel time data sets were inverted to tomographically image the uppermost mantle P wave (Pn) velocity, S wave (Sn) velocity, and the velocity ratio (V Pn /V Sn ). Furthermore, we modified the two-station method in order to limit the contributions of site response and estimate the effective attenuation of Sn phase (Q −1 Sn). Lower Q values generally correspond with lower velocities in terms of both Pn and Sn wave speeds (e.g., New England and the Mississippi Embayment), but some regions, including southern Georgia, eastern South Carolina, and the New Madrid Seismic Zone, show high velocity and low Q Sn values. This can be explained by scattering attenuation of the Sn phase. To estimate the uppermost mantle temperature, a constrained grid-search algorithm was conducted using the observed V Sn , V Pn , and Q Sn with the calculated velocities of specific compositional models. The uppermost mantle temperature result shows 300-500°C beneath the northern midcontinent and 1100°C beneath New England. Although our temperature results appear to be well resolved, we found that V Pn , V Sn , and Q Sn are not enough to constrain the detailed uppermost mantle composition model. Our results highlight significant temperature heterogeneity in the uppermost mantle across the CEUS and is consistent with there not being any melt within the uppermost mantle beneath the CEUS.

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Section: Temperature Implicationssupporting

confidence: 71%

Seismic Attenuation and Velocity Measurements of the Uppermost Mantle Beneath the Central and Eastern United States and Implications for the Temperature of the North American Lithosphere

2020

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“…Finally, a waveform matching method based on fitting attenuated versions of the estimated source time function to the observed waveforms has been applied to data from Iberia and Morocco (Bezada 2017) as well as Australia (Bezada & Smale 2019), and the Central Appalachians (Byrnes et al 2019) yielding results that are wellcorrelated to known geological features. This method is similar to the time-domain method of Adams & Humphreys (2010) and will also be described in more detail in a later section.…”

Section: Ln R( F )mentioning

confidence: 99%

On the robustness of attenuation measurements on teleseismic P waves: insights from micro-array analysis of the 2017 North Korean nuclear test

Bezada

Byrnes

Eilon

2019

Geophysical Journal International

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SUMMARY Despite their importance as a fundamental constraint on Earth properties, regional-scale measurements of body-wave seismic attenuation are scarce. This is partially a result of the difficulty in producing robust estimates of attenuation. In this paper, we focus on measuring differential attenuation on records of teleseismic P waves. We examine a unique data set of five records of the North Korean nuclear test of 2017 measured at five broad-band seismic stations deployed within a few metres of each other but using different installation procedures. Given their extreme proximity, we expect zero differential intrinsic attenuation between the different records. However, we find that different attenuation measurement methods and implementation parameters in fact produce significant apparent differential attenuation (Δt*). Frequency-domain methods yield a wide range of Δt* estimates between stations, depending on measurement bandwidth and nuances of signal processing. This measurement instability increases for longer time windows. Time domain methods are largely insensitive to the frequency band being considered but are sensitive to the time window that is chosen. We determine that signal-generated noise can affect measurements in both the frequency and time domain. In some cases, the range of results amounts to a significant fraction of the range of differential attenuation across the conterminous United States as determined by a recent study. We suggest some approaches to manage the inherent instability in these measurements and recommend best practices to confidently estimate body wave attenuation.

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“…Like other mountains in passive margin areas, the Appalachians, in their current mountain configuration, have been established in relation to passive margin tectonics, i.e. since recent geological times (Byrnes et al, 2019). to medium depth faults (less than 10-15 km), in this sector, they correspond to the activation of stalled faults, moving the most littoral sectors towards the northwest and the most continental sectors towards the southeast.…”

Section: Passive Margin Beadsmentioning

confidence: 92%

“…The foci are shallow, just over a few tens of km and often with a distensive component. The western sector of North America, from the axis of the St. Lawrence Valley to the southeastern Appalachians, is clearly one of the sectors where earthquakes of high magnitude (> 7) are expected, since many studies show that some have occurred in recent centuries (Ebel and Tuttle, 2002;Neely et al, 2018;Byrnes et al, 2019). Seismic activity is related to the opening dynamics of the Atlantic Ocean, although the authors include the role of the rebound of the continent that has been recovering since the last ice age (Ebel and Tuttle, 2002).…”

Section: Passive Margin Beadsmentioning

confidence: 99%

Quelle approche « réaliste » de la montagne en géographie : l’exemple des bourrelets de marge passive

Pech¹,

Séguier²

2020

l'Information Géographique

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The mountain is an essential object of geography but, like other objects, it opposes an approach offering elements of description and explanation based on a realistic, and above all geological representation, to another one more recent taking counts the representations of the populations. For the geography taught but also for the use which is made of it from a legislative point of view in France with the Mountain Law, the realistic approach dominates. The question is to know if this one, which bases a normative approach of the mountain is still valid in the light of the most recent scientific advances. The passive margin mountains, emblematic mountains of physical geography, are used here as an example of a type of mountain. From an in-depth analysis of the scientific literature, two points stand out: the recent genesis of these mountains, like all mountains on the surface of the earth, and the variety of their evolution. Putting geographic science into debate here does not consist in destroying its status in its function of cognitive action, in particular in the service of uses requested by society, but in recognizing the biases and limits of certain knowledges.

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Thin lithosphere beneath the central Appalachian Mountains: Constraints from seismic attenuation beneath the MAGIC array

Cited by 31 publications

References 69 publications

Seismic Attenuation and Velocity Measurements of the Uppermost Mantle Beneath the Central and Eastern United States and Implications for the Temperature of the North American Lithosphere

Seismic Attenuation and Velocity Measurements of the Uppermost Mantle Beneath the Central and Eastern United States and Implications for the Temperature of the North American Lithosphere

On the robustness of attenuation measurements on teleseismic P waves: insights from micro-array analysis of the 2017 North Korean nuclear test

Quelle approche « réaliste » de la montagne en géographie : l’exemple des bourrelets de marge passive

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