Seismic Structure of the Crust and Uppermost Mantle of North America and Adjacent Oceanic Basins: A Synthesis

Chulick, G. S.; Mooney, Walter D.

doi:10.1785/0120010188

Cited by 109 publications

(83 citation statements)

References 22 publications

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“…Several features in Figure 1a agree with known crustal structure of the western United States, including the thick crust beneath the central Rocky Mountains and the thin crust in the Basin and Range province (Chulick and Mooney, 2002). The histogram in Figure 1b shows a thickness distribution peaked at 36 km, close to the average thickness of the North American crust found by Chulick and Mooney (2002) to be 36.7 km. This depth is also close to the crust-mantle interface at 35 km in the IASP91 model (Kennett and Engdahl, 1991).…”

Section: Inversion With An Underparameterized Modelsupporting

confidence: 75%

Nonperturbational surface-wave inversion: A Dix-type relation for surface waves

Haney

Tsai

2015

GEOPHYSICS

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We extend the approach underlying the well-known Dix equation in reflection seismology to surface waves. Within the context of surface wave inversion, the Dix-type relation we derive for surface waves allows accurate depth profiles of shear-wave velocity to be constructed directly from phase velocity data, in contrast to perturbational methods. The depth profiles can subsequently be used as an initial model for nonlinear inversion. We provide examples of the Dix-type relation for under-parameterized and over-parameterized cases. In the under-parameterized case, we use the theory to estimate crustal thickness, crustal shear-wave velocity, and mantle shear-wave velocity across the Western U.S. from phase velocity maps measured at 8-, 20-, and 40-s periods. By adopting a thin-layer formalism and an over-parameterized model, we show how a regularized inversion based on the Dix-type relation yields smooth depth profiles of shearwave velocity. In the process, we quantitatively demonstrate the depth sensitivity of surface-wave phase velocity as a function of frequency and the accuracy of the Dix-type relation. We apply the over-parameterized approach to a nearsurface data set within the frequency band from 5 to 40 Hz and find overall agreement between the inverted model and the result of full nonlinear inversion.

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Section: Inversion With An Underparameterized Modelsupporting

confidence: 75%

Nonperturbational surface-wave inversion: A Dix-type relation for surface waves

Haney

Tsai

2015

GEOPHYSICS

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“…The Eastern Nicaraguan Rise comprises the region 7b (figures 6 and 7): the presence of a thickened oceanic type of crust is consistent with a Moho depth ranging from 19.5 km to 25.5 km and with the presence of a well developed low velocity channel in the upper mantle, while in region 7a (figures 6 and 7; Yucatan Basin, parts of Cayman Trough and Greater Antilles accretionary complex) the Moho depth is in the range 14.5 -24.5 km, with a lowest upper mantle velocity ranging from 4.0 km/s to 4.15 km/s and a high lower crust velocity (3.75 -3.95 km/s). The features shown in 7a are well consistent with previous results form seismic profiles studies [12]. Other curves, which were grouped as type 8 by the logical-combinatorial procedure, did not determine any specific region; therefore they have not been inverted.…”

Section: Discussionsupporting

confidence: 87%

“…The availability of data about the crust structure, summarized and generalized by several authors e.g. [4,10], the most recent regional studies [3,[11][12][13][14][15] and global studies [16][17][18] allow us now to make a refined study of the region. For this purpose we perform Rayleigh waves group velocity tomography, considering relatively short paths (regional trajectories), we regionalize the dispersion curves locally obtained by the tomography and we invert them, into average regionalized structural models, with a non-linear inversion scheme.…”

Section: Introductionmentioning

confidence: 99%

Crust and Upper Mantle Structure in the Caribbean Region by Group Velocity Tomography and Regionalization

González¹,

Álvarez²,

Guidarelli³

et al. 2007

Pure appl. geophys.

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An overview of the crust and upper mantle structure of the Central America and Caribbean region is presented as a result of the processing of more than 200 seismograms recorded by digital broadband stations from SSSN and GSN seismic networks. By FTAN analysis of the fundamental mode of the Rayleigh waves, group velocity dispersion curves are obtained in the period range from 10 s to 40 s; the error of these measurements varies from 0.06 and 0.10 km/s. From the dispersion curves, seven tomographic maps at different periods and with average spatial resolution of 500 km are obtained. Using the logical combinatorial classification techniques, eight main groups of dispersion curves are determined from the tomographic maps and eleven main regions, each one characterized by one kind of dispersion curves, are identified. The average dispersion curves obtained for each region are extended to 150 s by adding data from the tomographic study of [3] and inverted using a non-linear procedure. As a result of the inversion process, a set of models of the Swave velocity vs. depth in the crust and upper mantle are found. In six regions, we identify a typically oceanic crust and upper mantle structure, while in the other two the models are consistent with the presence of a continental structure. Two regions, located over the major geological zones of the accretionary crust of the Caribbean region, are characterized by a peculiar crust and upper mantle structure, indicating the presence of lithospheric roots reaching, at least, about 200 km of depth.2

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“…This process yielded 68 S-wave velocities at 27 different locations and 60 P-wave velocities at 22 different locations, which are listed in Table 2. Chulick and Mooney (2002), later updated by W. D. Mooney (personal comm., 2012), define crustal properties within four general regions of the CENA: (1) continental interior, (2) Gulf Coast, (3) Appalachian Mountains, and (4) Atlantic coast. All but one of the sites with reference rock velocities are located within the continental interior (13 sites), Atlantic coast region (17 sites), or Appalachian Mountains (2 sites).…”

Section: Evaluation Of Reference Velocitymentioning

confidence: 99%

Reference Rock Site Condition for Central and Eastern North America

Hashash

Kottke

Stewart

et al. 2014

Bulletin of the Seismological Society of America

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The reference rock site condition has two important applications for ground-motion prediction in the stable continental region of central and eastern North America (CENA). (1) It represents the site condition for which ground motions are computed using semiempirical ground-motion prediction equations. In addition, (2) it represents the site condition to which site amplification factors, which are used to modify ground-motion intensity measures for softer site condition, are referenced (i.e., site amplification is unity for reference rock). We define reference rock by its shear (S)-and compression (P)-wave velocities, as well as a site attenuation parameter (κ 0 ), which is used in stochastic ground-motion simulation methods. Prior definitions of reference rock conditions in CENA were based mostly on indirect large-scale crustal velocity inversions and judgment. We compile and interpret a unique database of direct velocity measurements to develop criteria for assessing the presence of reference rock site condition based on measured seismic velocities and their gradient with respect to depth. We apply the criteria to available profiles and perform rigorous statistical analysis from which we recommend S-and P-wave velocities of 3000 and 5500 m=s, respectively, for the reference rock condition. We recommend that, for practical applications, use ranges of reference S-and P-wave velocities of 2700-3300 m=s and 5000-6100 m=s, respectively. The ranges are based on a 5% change in amplification using quarterwavelength theory. We do not find evidence for regional dependence of the reference velocities, which are derived principally from three general geographic regions: (1) Atlantic coast, (2) continental interior, and (3) Appalachian Mountains. Our data do not provide reference velocities for the Gulf Coast region. The recommended velocity-compatible reference rock site kappa is 0.006 s.

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Seismic Structure of the Crust and Uppermost Mantle of North America and Adjacent Oceanic Basins: A Synthesis

Cited by 109 publications

References 22 publications

Nonperturbational surface-wave inversion: A Dix-type relation for surface waves

Nonperturbational surface-wave inversion: A Dix-type relation for surface waves

Crust and Upper Mantle Structure in the Caribbean Region by Group Velocity Tomography and Regionalization

Reference Rock Site Condition for Central and Eastern North America

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