Long‐Period Rayleigh Wave Phase Velocity Tomography Using USArray

Babikoff, Jordyn; Dalton, C. A.

doi:10.1029/2018gc008073

Cited by 22 publications

(41 citation statements)

References 47 publications

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“…In Figure 13b we only include an event‐specific

false| \nabla τ {false|}^{2}

value in the median calculation if the distance between the earthquake and pixel is

< 115

degrees, and in Figure 13c only

false| \nabla τ {false|}^{2}

values from earthquakes

> 115

degrees are included. For this test we use the Rayleigh wave Eikonal maps of Babikoff and Dalton (). Figure 13d shows that the number of distant events (

> 115

degrees) is much smaller than the number of nearby events (

< 115

degrees).…”

Section: Discussionmentioning

confidence: 99%

“…Eikonal phase velocities for 100 s Rayleigh waves calculated from the database of Babikoff and Dalton () for measurements grouped into different subsets based on path length. (a) All measurements are used.…”

Section: Discussionmentioning

confidence: 99%

“…While the focus of this study is synthetic seismograms, we also show some Rayleigh wave travel-time and amplitude measurements made on real data, using the data set of Babikoff and Dalton (2019). These measurements, which exist for the period range 25-180 s, were made using ASWMS (Jin & Gaherty, 2015) on waveforms recorded by 1831 USArray stations.…”

Section: Measurement Approachesmentioning

confidence: 99%

“…Figure 11. Evidence of the interference in real data using the 100-s Rayleigh wave travel-time and amplitude measurements from Babikoff and Dalton (2019) for two events, 201204150557 (a-c) and 201209140451 (d-f). Event 201204150557 is located at 90.31 o E, 2.49 o N, and 33.0-km depth.…”

Section: Implications For Usarray Measurements and Phase Velocity Mapsmentioning

confidence: 99%

“…Path-averaged dc/c predicted by integrating through the GDM52 phase-velocity map is subtracted from the measured values. Results are shown for 208,233 measurements at USArray stations (Babikoff & Dalton, 2019) and 282,996 measurements at global stations (Ekström, 2011). (b) Median absolute phase-velocity difference (m/s) in the contiguous U.S. between 549 event-specific Eikonal maps of Babikoff and Dalton (2019) and the U.S. portion of the GDM52 global map.…”

Section: Implications For Usarray Measurements and Phase Velocity Mapsmentioning

confidence: 99%

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Evidence of Overtone Interference in Fundamental‐Mode Rayleigh Wave Phase and Amplitude Measurements

Hariharan

Dalton

et al. 2020

JGR Solid Earth

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We present evidence that measurements of minor-arc fundamental-mode (FM) Rayleigh waves experience interference from major-arc overtones, resulting in travel-time and amplitude measurements oscillating along a ray path. The oscillations are present in synthetic seismograms generated in a 3-D Earth model via SPECFEM3D_GLOBE and in a 1-D Earth model by mode summation. The absence of oscillations in synthetics containing only the FM indicates that the oscillations originate from higher-mode interference. This interference is present across multiple measurement techniques, including multi-channel cross correlation, phase-matched filtering, and cluster analysis. Experiments with 1-D synthetics suggest that contamination from interference is largest at epicentral distances greater than around 120 degrees, where record sections of seismograms show the major-arc overtones intersecting the minor-arc FM Rayleigh wave. The short wavelength of the interference pattern means it is only observable with dense station spacing and high data quality, which may explain why it has not, to our knowledge, been previously recognized. We show the interference is visible in real data. Its overall impact on phase-velocity maps is probably minor due to many measurements from shorter path lengths less prone to interference bias. However, phase-velocity maps constructed only from measurements at epicentral distances prone to interference exhibit significant noise and poor agreement with maps from measurements that include all path lengths; the issue is especially problematic for approaches that use differential travel times between nearby stations. Accounting for interference may diminish noise in measurements and improve the accuracy of images of the upper mantle.

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“…In Figure 13b we only include an event‐specific

false| \nabla τ {false|}^{2}

value in the median calculation if the distance between the earthquake and pixel is

< 115

degrees, and in Figure 13c only

false| \nabla τ {false|}^{2}

values from earthquakes

> 115

degrees are included. For this test we use the Rayleigh wave Eikonal maps of Babikoff and Dalton (). Figure 13d shows that the number of distant events (

> 115

degrees) is much smaller than the number of nearby events (

< 115

degrees).…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Measurement Approachesmentioning

confidence: 99%

Section: Implications For Usarray Measurements and Phase Velocity Mapsmentioning

confidence: 99%

Section: Implications For Usarray Measurements and Phase Velocity Mapsmentioning

confidence: 99%

See 3 more Smart Citations

Evidence of Overtone Interference in Fundamental‐Mode Rayleigh Wave Phase and Amplitude Measurements

Hariharan

Dalton

et al. 2020

JGR Solid Earth

Self Cite

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Evaluating models for lithospheric loss and intraplate volcanism beneath the Central Appalachian Mountains

Long

Wagner

King

et al. 2021

Preprint

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The eastern margin of North America has been shaped by a series of tectonic events including the Paleozoic Appalachian Orogeny and the breakup of Pangea during the Mesozoic. For the past ∼200 Ma, eastern North America has been a passive continental margin; however, there is evidence in the Central Appalachian Mountains for post-rifting modification of lithospheric structure. This evidence includes two co-located pulses of magmatism that post-date the rifting event (at 152 and 47 Ma) along with low seismic velocities, high seismic attenuation, and high electrical conductivity in the upper mantle. Here, we synthesize and evaluate constraints on the lithospheric evolution of the Central Appalachian Mountains. These include tomographic imaging of seismic velocities, seismic and electrical conductivity imaging along the Mid-Atlantic Geophysical Integrative Collaboration array, gravity and heat flow measurements, geochemical and petrological examination of Jurassic and Eocene magmatic rocks, and estimates of erosion rates from geomorphological data. We discuss and evaluate a set of possible mechanisms for lithospheric loss and intraplate volcanism beneath the region. Taken together, recent observations provide compelling evidence for lithospheric loss beneath the Central Appalachians; while they cannot uniquely identify the processes associated with this loss, they narrow the range of plausible models, with important implications for our understanding of intraplate volcanism and the evolution of continental lithosphere. Our preferred models invoke a combination of (perhaps episodic) lithospheric loss via Rayleigh-Taylor instabilities and subsequent small-scale mantle flow in combination with shear-driven upwelling that maintains the region of thin lithosphere and causes partial melting in the asthenosphere. Plain Language SummaryFor the past 200 million years, the east coast of North America has been situated in the middle of a tectonic plate. Contrary to the expectations for this setting, a region of the Central Appalachian Mountains centered near the boundary between the U.S. states of Virginia and West Virginia exhibits atypical properties. The unusual observations include volcanic activity in the geologic past far away from a plate boundary, elevated rates of erosion associated with high topography in the Central Appalachians, and anomalous structure in the upper mantle that has been detected using geophysical methods. This article describes, synthesizes, and compares a suite of observations that show that this part of the Central Appalachians is unusual compared to other so-called passive continental margins. We discuss a range of different models that might describe how the lithosphere, or the rigid part of the crust and upper mantle that defines the tectonic plate, has evolved through time beneath our study region. We show that the lithosphere today is thin, and that past episodes of lithospheric loss involving a portion of dense lithosphere "dripping" into the mantle under the force of gravity may provide a goo...

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Shear-wave velocity structure beneath Alaska from a Bayesian joint inversion of Sp receiver functions and Rayleigh wave phase velocities

Gama

Fischer

Eilon

et al. 2021

Earth and Planetary Science Letters

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Long‐Period Rayleigh Wave Phase Velocity Tomography Using USArray

Cited by 22 publications

References 47 publications

Evidence of Overtone Interference in Fundamental‐Mode Rayleigh Wave Phase and Amplitude Measurements

Evidence of Overtone Interference in Fundamental‐Mode Rayleigh Wave Phase and Amplitude Measurements

Evaluating models for lithospheric loss and intraplate volcanism beneath the Central Appalachian Mountains

Shear-wave velocity structure beneath Alaska from a Bayesian joint inversion of Sp receiver functions and Rayleigh wave phase velocities

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