Inferring Earth’s discontinuous chemical layering from the 660-kilometer boundary topography

Science ◽  
2019 ◽  
Vol 363 (6428) ◽  
pp. 736-740 ◽  
Author(s):  
Wenbo Wu ◽  
Sidao Ni ◽  
Jessica C. E. Irving
Keyword(s):  
Solid Earth ◽  
Long Range ◽  
Upper Mantle ◽  
Lower Mantle ◽  
Seismic Waves ◽  
Short Length ◽  
Small Scale ◽  
Length Scale ◽  
Scale Roughness ◽  
Topographic Variation

Topography, or depth variation, of certain interfaces in the solid Earth can provide important insights into the dynamics of our planet interior. Although the intermediate- and long-range topographic variation of the 660-kilometer boundary between Earth’s upper and lower mantle is well studied, small-scale measurements are far more challenging. We found a surprising amount of topography at short length scale along the 660-kilometer boundary in certain regions using scatteredP'P'seismic waves. Our observations required chemical layering in regions with high short-scale roughness. By contrast, we did not see such small-scale topography along the 410-kilometer boundary in the upper mantle. Our findings support the concept of partially blocked or imperfect circulation between the upper and lower mantle.

Decoupling small-scale roughness and long-range features on deep reactive ion etched silicon surfaces

2013 ◽  
Vol 114 (11) ◽  
pp. 113506 ◽  
Author(s):  
Frank W. DelRio ◽  
Lawrence H. Friedman ◽  
Michael S. Gaither ◽  
William A. Osborn ◽  
Robert F. Cook
Keyword(s):  
Long Range ◽  
Silicon Surfaces ◽  
Small Scale ◽  
Etched Silicon ◽  
Scale Roughness

scholarly journals A Two-Scale Approach for Lubricated Soft-Contact Modeling: An Application to Lip-Seal Geometry

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Michele Scaraggi ◽  
Giuseppe Carbone
Keyword(s):  
Large Scale ◽  
Mixed Lubrication ◽  
Small Scale ◽  
Length Scale ◽  
Contact Modeling ◽  
Soft Contact ◽  
Lip Seal ◽  
Contact Algorithm ◽  
Scale Roughness ◽  
Lubrication Conditions

We consider the case of soft contacts in mixed lubrication conditions. We develop a novel, two scales contact algorithm in which the fluid- and asperity-asperity interactions are modeled within a deterministic or statistic scheme depending on the length scale at which those interactions are observed. In particular, the effects of large-scale roughness are deterministically calculated, whereas those of small-scale roughness are included by solving the corresponding homogenized problem. The contact scheme is then applied to the modeling of dynamic seals. The main advantage of the approach is the tunable compromise between the high-computing demanding characteristics of deterministic calculations and the much lower computing requirements of the homogenized solutions.

scholarly journals Power spectra of random heterogeneities in the solid earth

Solid Earth ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 275-292 ◽  
Author(s):  
Haruo Sato
Keyword(s):  
Solid Earth ◽  
Power Law ◽  
Upper Mantle ◽  
Spectral Envelope ◽  
Small Scale ◽  
Mean Square ◽  
Statistical Characterization ◽  
The Earth ◽  
Power Law Decay ◽  
Wide Range

Abstract. Recent seismological observations focusing on the collapse of an impulsive wavelet revealed the existence of small-scale random heterogeneities in the earth medium. The radiative transfer theory (RTT) is often used for the study of the propagation and scattering of wavelet intensities, the mean square amplitude envelopes through random media. For the statistical characterization of the power spectral density function (PSDF) of the random fractional fluctuation of velocity inhomogeneities in a 3-D space, we use an isotropic von Kármán-type function characterized by three parameters: the root mean square (RMS) fractional velocity fluctuation, the characteristic length, and the order of the modified Bessel function of the second kind, which leads to the power-law decay of the PSDF at wavenumbers higher than the corner. We compile reported statistical parameters of the lithosphere and the mantle based on various types of measurements for a wide range of wavenumbers: photo-scan data of rock samples; acoustic well-log data; and envelope analyses of cross-hole experiment seismograms, regional seismograms, and teleseismic waves based on the RTT. Reported exponents of wavenumber are distributed between −3 and −4, where many of them are close to −3. Reported RMS fractional fluctuations are on the order of 0.01–0.1 in the crust and the upper mantle. Reported characteristic lengths distribute very widely; however, each one seems to be restricted by the dimension of the measurement system or the sample length. In order to grasp the spectral characteristics, eliminating strong heterogeneity data and the lower mantle data, we have plotted all the reported PSDFs of the crust and the upper mantle against wavenumber for a wide range (10−3–108 km−1). We find that the spectral envelope of those PSDFs is well approximated by the inverse cube of wavenumber. It suggests that the earth-medium randomness has a broad spectrum. In theory, we need to re-examine the applicable range of the Born approximation in the RTT when the wavenumber of a wavelet is much higher than the corner. In observation, we will have to carefully measure the PSDF on both sides of the corner. We may consider the obtained power-law decay spectral envelope as a reference for studying the regional differences. It is interesting to study what kinds of geophysical processes created the observed power-law spectral envelope at different scales and in different geological environments in the solid earth medium.

scholarly journals Power Spectra of Random Heterogeneities of the Solid Earth

2018 ◽  
Author(s):  
Haruo Sato
Keyword(s):  
Solid Earth ◽  
Power Law ◽  
Upper Mantle ◽  
Spectral Envelope ◽  
Small Scale ◽  
Mean Square ◽  
Statistical Characterization ◽  
The Earth ◽  
Power Law Decay ◽  
Wide Range

Abstract. Recent seismological observations focusing on the collapse of an impulsive wavelet revealed the existence of small-scale random heterogeneities in the earth medium. The radiative transfer theory (RTT) is often used for the study of the propagation and scattering of wavelet intensities, the mean square amplitude envelopes. For the statistical characterization of the power spectral density function (PSDF) of the random fractional fluctuation of velocity inhomogeneities in a 3D space, we use von Karman type with three parameters: the root mean square (RMS) fractional velocity fluctuation, the characteristic length, and the order of the modified Bessel function of the second kind, which leads to the power-law decay of PSDF at wavenumbers higher than the corner. We compile reported statistical parameters of the lithosphere and the mantle based on various types of measurements for a wide range of wavenumbers: photo scan data of rock samples, acoustic well log data, and envelope analyses of cross-hole experiment seismograms, regional seismograms and tele-seismic waves based on the RTT. Reported exponents of wavenumber are distributed between −3 and −4, where many of them are close to −3. Reported RMS fractional fluctuations are of the order of 0.01 ~ 0.1 in the crust and the upper mantle. Reported characteristic lengths distribute very widely, however, each one seems to be restricted by the dimension of the measurement system or the sample length. In order to grasp the spectral characteristics, eliminating strong heterogeneity data and the lower mantle data, we have plotted all the reported PSDFs of the crust and the upper mantle against wavenumber for a wide range 10−3 ∼ 108 km−1. We find that the envelope of those PSDFs is well approximated by the −3rd power of wavenumber. It suggests that the earth medium randomness has a broad spectrum. In theory, we need to re-examine the applicable range of the Born approximation in the RTT when the wavenumber of a wavelet is much higher than the corner. In observation, we will have to measure carefully the PSDF on both sides of the corner. We may consider the obtained power-law decay spectral envelope as a reference for studying the regional differences. It is interesting to study what kinds of geophysical processes created the observed power-law spectral envelope in different scales and in different portions of the solid earth medium.

Annealing of metamict gadolinite-(Y): X-ray diffraction, Raman, IR, and Mössbauer spectroscopy

2019 ◽  
Vol 234 (9) ◽  
pp. 587-593 ◽  
Author(s):  
Carsten Paulmann ◽  
Peter Zietlow ◽  
Catherine McCammon ◽  
Ekhard K.H. Salje ◽  
Ulrich Bismayer
Keyword(s):  
Long Range ◽  
Room Temperature ◽  
Short Length ◽  
Length Scale ◽  
Experimental Uncertainty ◽  
X Ray Diffraction ◽  
X Ray ◽  
Radiation Induced ◽  
Long Range Ordering ◽  
Increasing Temperature

Abstract Radiation induced disorder in gadolinite that led to metamictization with an upper degree of amorphization of 18% was thermally annealed between room temperature and 1273 K. The degree of annealing was calibrated using the anti-symmetric Si–O–Si Raman-active stretching mode near 902 cm−1. Annealing increased with increasing temperature with a rapid critical recrystallization at ca. 943 K. This annealing on a short length scale was then complemented by investigations of long-range ordering seen by X-ray diffraction. The same critical temperature was found, and in addition further increase of long-range order extended to 1073 K. Metamict gadolinite contains only Fe2+ within experimental uncertainty.

scholarly journals Feedbacks between a non-Newtonian upper mantle, mantle viscosity structure and mantle dynamics

2020 ◽  
Vol 224 (2) ◽  
pp. 961-972
Author(s):  
A G Semple ◽  
A Lenardic
Keyword(s):  
Upper Mantle ◽  
Lower Mantle ◽  
Mantle Convection ◽  
Mantle Flow ◽  
Mantle Dynamics ◽  
Plate Motions ◽  
Low Viscosity ◽  
Mantle Viscosity ◽  
Flow Feature ◽  
Mantle Rheology

SUMMARY Previous studies have shown that a low viscosity upper mantle can impact the wavelength of mantle flow and the balance of plate driving to resisting forces. Those studies assumed that mantle viscosity is independent of mantle flow. We explore the potential that mantle flow is not only influenced by viscosity but can also feedback and alter mantle viscosity structure owing to a non-Newtonian upper-mantle rheology. Our results indicate that the average viscosity of the upper mantle, and viscosity variations within it, are affected by the depth to which a non-Newtonian rheology holds. Changes in the wavelength of mantle flow, that occur when upper-mantle viscosity drops below a critical value, alter flow velocities which, in turn, alter mantle viscosity. Those changes also affect flow profiles in the mantle and the degree to which mantle flow drives the motion of a plate analogue above it. Enhanced upper-mantle flow, due to an increasing degree of non-Newtonian behaviour, decreases the ratio of upper- to lower-mantle viscosity. Whole layer mantle convection is maintained but upper- and lower-mantle flow take on different dynamic forms: fast and concentrated upper-mantle flow; slow and diffuse lower-mantle flow. Collectively, mantle viscosity, mantle flow wavelengths, upper- to lower-mantle velocities and the degree to which the mantle can drive plate motions become connected to one another through coupled feedback loops. Under this view of mantle dynamics, depth-variable mantle viscosity is an emergent flow feature that both affects and is affected by the configuration of mantle and plate flow.

African Hot Spot Volcanism: Small-Scale Convection in the Upper Mantle Beneath Cratons

Science ◽  
2000 ◽  
Vol 290 (5494) ◽  
pp. 1137-1140 ◽  
Author(s):  
S. D. King
Keyword(s):  
Upper Mantle ◽  
Hot Spot ◽  
Small Scale

Small scale heterogeneity in the mid-lower mantle beneath the circum-Pacific area

2010 ◽  
Vol 183 (1-2) ◽  
pp. 91-103 ◽  
Author(s):  
Satoshi Kaneshima ◽  
George Helffrich
Keyword(s):  
Lower Mantle ◽  
Small Scale ◽  
Scale Heterogeneity ◽  
Pacific Area
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