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Monday, July 27, 2020 | History

2 edition of seismic attenuation structure of the East Pacific Rise found in the catalog.

seismic attenuation structure of the East Pacific Rise

William Sam Douglas Wilcock

seismic attenuation structure of the East Pacific Rise

by William Sam Douglas Wilcock

  • 107 Want to read
  • 24 Currently reading

Published by Woods Hole Oceanographic Institution in Woods Hole, Mass .
Written in English

    Subjects:
  • Seismic tomography -- Pacific Ocean.,
  • Sea-floor spreading.

  • Edition Notes

    Statementby William Sam Douglas Wilcock.
    SeriesWHOI -- 92-17., WHOI (Series) -- 92-17.
    ContributionsWoods Hole Oceanographic Institution., Massachusetts Institute of Technology.
    The Physical Object
    Pagination337 p. :
    Number of Pages337
    ID Numbers
    Open LibraryOL15182267M

    Models of seismic attenuation as a function of depth through the mantle are difficult to determine. Normal mode and surface waves have been used but use long wavelength waves and thus can only resolve broad scale structure. Body waves such as multiple ScS phases have been used for regional mantle attenuation studies but lack vertical resolution. Seismic-wave attenuation (1/Q) is thought to be highly sensitive to variations in temperature, and joint interpretation of attenuation and velocity models should aid in distinguishing between thermal and chemical heterogeneity in the mantle. However, global attenuation tomography has thus far contributed little to our understanding of Earth structure, and the existing 3-D global Q models show.

    Summary. We present QADR17, a global model of Rayleigh-wave attenuation based on a massive surface wave data set ( frequency-dependent attenuation curve. Up to s, three very attenuating zones appear, one under the East Pacific Rise (E.P.R), another one around Hawaii, a third one east of Kermadec. By inversion, those three anomalies are found.

    Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and Woods Hole Oceanographic. PDF | The Table of Contents is for the book Rock Quality, Seismic Velocity, Attenuation and Anisotropy. This is a pages wide-ranging review of | Find, read and cite all the research you.


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Seismic attenuation structure of the East Pacific Rise by William Sam Douglas Wilcock Download PDF EPUB FB2

Robert A. Dunn, Douglas R. Toomey, Sean C. Solomon, Three‐dimensional seismic structure and physical properties of the crust and shallow mantle beneath the East Pacific Rise at 9°30'N, Journal of Geophysical Research: Solid Earth, /JB,B10, (), ().Cited by: Omid Aghaei, Mladen R.

Nedimović, Milena Marjanović, Suzanne M. Carbotte, J. Pablo Canales, Hélène Carton, Nikola Nikić, Constraints on melt content of off‐axis magma lenses at the East Pacific Rise from analysis of 3‐D seismic amplitude variation with angle of incidence, Journal of Geophysical Research: Solid Earth, Cited by: The first evidence of structure within the inner core came from studies of seismic attenuation, which found relatively high levels of attenuation in the uppermost – km of the inner core.

More recently, it has been determined that the inner core is seismically anisotropic, with P -wave speeds being larger in the direction parallel to. Magnetotelluric and seismic data, collected during the MELT experiment at the southern East Pacific Rise 1,2, constrain the distribution of melt beneath this mid-ocean-ridge spreading centre and Cited by:   The East Pacific Rise (EPR) between 9° and 10° N is the most extensively studied section of the global ridge system Here the Cocos and Pacific Cited by: The East Pacific Rise velocity structures More porosity and fracture aspect ratio theories First sub-Pacific ocean core with sonic logs and permeability tests Attenuation and seismic Q due to fracturing and alteration Seismic attenuation tomography across the East Pacific Rise.

Ting Chen, Robert W. Clayton, Seismic attenuation structure in central Mexico: Image of a focused high‐attenuation zone in the mantle wedge, Journal of Geophysical Research: Solid Earth, /JB,B7, (). Mantle attenuation at MORs has received relatively little attention; global models show low Q S (50 to 60) in the upper km close to the ridge, whereas a single regional study found surprisingly high Q S (≈70) at the East Pacific Rise (EPR) using surface waves, at odds with low shear velocities.

Surface wave studies provide good vertical. Given that NoMelt asthenospheric attenuation is moderate and weaker than the asthenospheric attenuation measured at the East Pacific Rise (Yang et al., ) and Juan de Fuca ridge (Ruan et al., ), we conclude that our results are not consistent with an important role for melt.

Wilcock, W. et al. Seismic attenuation structure of the East Pacific Rise near 9° 30′ N. Geophys. Res.– () ADS Article Google Scholar. A recent global, tomographic model of attenuation considering focusing effects on amplitude finds attenuation at 50 s period on the East Pacific Rise that is ∼ 17% higher than our estimate for MELT and ∼ 72% greater than for the off-axis GLIMPSE area.

In the period range where the two studies overlap, the values are consistent within their. Robert A. Sohn, Spahr C. Webb, John A. Hildebrand, Fine‐scale seismic structure of the shallow volcanic crust on the East Pacific Rise at 9°50′N, Journal of Geophysical Research: Solid Earth, /JB,B12, ().

Muawia Barazangi, Bryan Isacks, Lateral variations of seismic‐wave attenuation in the upper mantle above the inclined earthquake zone of the Tonga Island Arc: Deep anomaly in the upper mantle, Journal of Geophysical Research, /JBip, 76, 35, (), ().

Seismic attenuation tomography across the East Pacific Rise Continuous sub-ocean floor seismic profiles 28/09/ Page VII. BibTeX @MISC{Hole92theseismic, author = {Woods Hole and William Sam and Douglas Wilcock and William Sam and Douglas Wilcock and Woods Hole and Woods Hole and G.

Michael Pr and Rm N and John W. Farringto Dstributgon I and Avatlabeijty Cudis and Dist Ai J Jldior and William Sam and Douglas Wilcock}, title = {THE SEISMIC ATTENUATION STRUCTURE OF THE EAST PACIFIC RISE}, year =.

Seismic methods and seafloor compliance techniques are two complementary tools that can be used to constrain seafloor structure. We have performed an analysis of both types of data recorded on-axis at 9°33′N on the East Pacific Rise to obtain a shear wave structure for the upper oceanic crust.

A model of Q β as a function of depth has been determined for the upper mantle beneath the East Pacific Rise. The model is appropriate for shear waves with periods from roughly 15 to 30 s.

The amplitudes of multibounce SH phases which propagate within the upper mantle were used to constrain the Q structure. The multibounce phase amplitudes were measured with respect to the S wave. R.A.

Dunn, D. Toomey, S.C. SolomonThree-dimensional seismic structure and physical properties of the crust and shallow mantle beneath the East Pacific Rise at 9º30′N J. Geophys. Res., (), pp. Attenuation structure through the Earth's subsurface.

Global attenuation model below has been obtained from the normal modes and surface waves displays the highest attenuation in the asthenosphere and inner core and low attenuation in the lithosphere and lower mantle (Figure 4).Global surface wave attenuation models correspond closely with shear velocity, suggesting that the.

Three-dimensional seismic structure and physical properties of the crust and shallow mantle beneath the East Pacific Rise at 9° 30′ N.

Geophys. Res. In the spring ofwe undertook an extensive geophysical study of the Clipperton Fracture Zone (FZ) on the fast spreading East Pacific Rise.

The Clipperton Area Seismic Study to Investigate Compensation experiment (CLASSIC) included surveys to examine the deep structures associated with the fracture zone and adjacent northern ridge segment.

In this paper, we report the results from five.This study uses inversions of isotropic and anisotropic seismic structure with geodynamic models to examine the mantle dynamics and rheology beneath the MELT region of the East Pacific Rise (EPR).The two-dimensional P-wave attenuation structure of the axial crust of the East Pacific Rise was obtained from an inversion of waveform spectra collected during an active-source seismic tomography experiment.

The structure shows that attenuation near the surface is high everywhere but decreases markedly within 1 to 3 kilometers of the rise axis.