Lower Mantle Lateral Heterogeneity Beneath the Caribbean Sea

Tibuleac, I. M.; Herrin, Eugene

doi:10.1126/science.285.5434.1711

Cited by 9 publications

(3 citation statements)

References 16 publications

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“…Smaller-scale plume or slab features that are below the current resolution of global seismic tomography, but can be resolved in regional-scale inversions (e.g., Hung et al, 2005;Wysession et al, 2001), exist in the D 00 region as well. Innovative scattering analysis or array imaging may prove to be the only means by which to constrain even smaller-scale structures (e.g., Ji and Nataf, 1998;Tibuleac and Herrin, 1999;Tilmann et al, 1998). The characterization of LLSVPs is rapidly improving and more detailed than for any of the smaller-scale structures, so this section will focus on them.…”

Section: Large Low-shear-velocity Provincesmentioning

confidence: 99%

Deep Earth Structure: Lower Mantle and D″

Lay

2015

Treatise on Geophysics

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Section: Large Low-shear-velocity Provincesmentioning

confidence: 99%

Deep Earth Structure: Lower Mantle and D″

Lay

2015

Treatise on Geophysics

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“…For instance PREM predicts slowness magnitudes of 2.7 s/deg for PcP and 0.71 s/deg for PKiKP , and the expected backazimuth is 145°. Slowness anomalies at arrays are not uncommon and can arise because of deep earth velocity heterogeneities [ Kanasewich et al , 1972; Tibuleac and Herrin , 1999], near receiver site effects [ Lin and Roecker , 1996; Tibuleac and Herrin , 1997], or intra‐array velocity variations, including topography [ Bokelmann , 1995]. Accounting for such anomalies is critical when slownesses are used in event location, and a large amount of effort has gone into calibrating various array stations and generating corrective slowness perturbations [ Koch and Kradolfer , 1997; Bondar and North , 1999; Bondar et al , 1999].…”

Section: Validation Of the Pkikp‐pcp Timesmentioning

confidence: 99%

Constraints on aspherical core structure from PKiKP‐PcP differential travel times

2003

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[1] We have assembled a data set of 302 differential PKiKP-PcP travel times that were recorded by seismic array stations of the International Monitoring System. This is an order of magnitude more data than all previous PKiKP-PcP observations combined. The differential times were measured using a beam-forming and cross-correlation algorithm that has a precision of 1-2 sampling intervals (<0.1 s). The use of differential times mitigates the effects of hypocentral errors and heterogeneities in the crust and upper mantle, leaving the data sensitive to deep Earth structure. The PKiKP-PcP times are especially sensitive to variations in the thickness of the liquid outer core. The data are well fit by PREM, with residuals having a mean of À0.29 s and a standard deviation of 0.44 s, and rule out lateral variations in outer core thickness of more than 4 km. Most of the geographically coherent residuals can be explained by lower mantle heterogeneities and ellipticity corrections however there remain at least three regions that seem to require aspherical core structure. The anomalous data are best explained by long-wavelength topography on the core-mantle boundary (CMB) with peak-to-peak amplitude of 3.5 km. The CMB topography is most likely maintained by isostatic compensation of thickness variations in a distinct layer at the base of the mantle.

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“…Slowness and azimuthal anomalies of teleseismic P phases measured at seismic arrays have been used to infer mantle and crustal structure. An early controversy was related to whether the anomalies were caused by near-receiver structure in the upper mantle and crust, or in the lower mantle; results are summarized in more recent studies such as Steck and Prothero (1993), Lin and Roecker (1996), and Tibuleac and Herrin (1999). Most of these studies were conducted in the short-period (ϳ1 Hz) band.…”

Section: Introductionmentioning

confidence: 99%

Large Teleseismic P Wavefront Deflections Observed with Broadband Arrays

Schulte-Pelkum

Vernon

Eakins

2003

Bulletin of the Seismological Society of America

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We measure the plane wavefront incidence azimuth for teleseismic P at large-aperture (ϳ50 km) broadband arrays. The incidence azimuth is determined by crosscorrelation of the P arrivals on the vertical component seismograms filtered in successive frequency bands. The periods considered range from 10 to 35 sec. At the Anza array in southern California, the plane wave direction is deflected from the great circle azimuth of the event by up to 20Њ. In addition, we find a surprisingly strong frequency dependence of the same magnitude and a striking antisymmetric pattern of the deflection as a function of backazimuth, whereas the curvature of the wavefront is small. Similar characteristics are found at the Gräfenberg array in Germany and the NORSAR array in Norway, however, with much weaker amplitudes of ϳ5Њ. We ascribe the behavior at Anza to structure in the lower crust and uppermost mantle beneath the array, given that the observations are only a function of source backazimuth and not of source depth and source mechanism, that the wavelengths under consideration range from 50 to 270 km, and that the sign of the deviation is opposite to that predicted from shallow crustal structure and Moho topography. We are able to reproduce the magnitude and frequency dependence of the wavefront deflection using finite difference numerical modeling of plane wave propagation through simple 2D structures.

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Lower Mantle Lateral Heterogeneity Beneath the Caribbean Sea

Cited by 9 publications

References 16 publications

Deep Earth Structure: Lower Mantle and D″

Deep Earth Structure: Lower Mantle and D″

Constraints on aspherical core structure from PKiKP‐PcP differential travel times

Large Teleseismic P Wavefront Deflections Observed with Broadband Arrays

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