The SCEC Southern California Reference Three-Dimensional Seismic Velocity Model Version 2

Magistrale, Harold; Day, Steven M.; Clayton, Robert W.; Graves, Robert

doi:10.1785/0120000510

Cited by 257 publications

(277 citation statements)

References 36 publications

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“…Our observations that the upper mantle anomaly below the eastern Transverse Ranges extends to greater depths where the crust is thicker (Magistrale et al, 2000) than the western end may be evidence for a higher convergence rate or longer period of convergence in the eastern Transverse Ranges as suggested by fission-track data (Blythe et al, 2000). There is also high spatial correlation between the depth of the intact mantle downwelling and topography.…”

Section: Resolution Testsmentioning

confidence: 50%

“…One of the main differences between this uppermost mantle velocity model and earlier models is that this model uses previously determined crustal velocities and Moho depth variations from the SCEC reference seismic velocity model version 2 (Magistrale et al, 2000) to remove the effects of crustal heterogeneity on the teleseismic travel times. Before inversion, each teleseismic ray is ray-traced through the three-dimensional crustal model to a depth of 45 km, deeper than the maximum Moho depth, to ensure that the entire crust is included in the crustal correction.…”

Section: Inversion Methodsmentioning

confidence: 99%

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Mantle Heterogeneities and the SCEC Reference Three-Dimensional Seismic Velocity Model Version 3

Kohler¹

2003

Bulletin of the Seismological Society of America

128

133

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We determine upper mantle seismic velocity heterogeneities below Southern California from the inversion of teleseismic travel-time residuals. Teleseismic P-wave arrival times are obtained from three temporary passive experiments and Southern California Seismic Network (SCSN) stations, producing good raypath coverage. The inversion is performed using a damped least-squares conjugate gradient method (LSQR). The inversion model element spacing is 20 km. Before the inversion, the effects of crustal velocity heterogeneities represented by the Southern California Earthquake Center (SCEC) seismic velocity model version 2 are removed from the teleseismic travel times. The P-wave inversion produces a variance reduction of 43%. S-wave velocities are determined from laboratory Vp/Vs ratios. The most prominent features imaged in the results are high P-wave velocities ‫)%3ם(‬ in the uppermost mantle beneath the northern Los Angeles basin, and the previously reported tabular high-velocity anomaly ‫)%3ם(‬ to depths of 200 km beneath the Transverse Ranges, crosscutting the San Andreas fault. We incorporate the upper mantle seismic velocity heterogeneities into the SCEC Southern California reference seismic velocity model. The prior accounting for the crustal velocity heterogeneity demonstrates the utility of the top-down method of the SCEC seismic velocity model development.

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Section: Resolution Testsmentioning

confidence: 50%

Section: Inversion Methodsmentioning

confidence: 99%

Mantle Heterogeneities and the SCEC Reference Three-Dimensional Seismic Velocity Model Version 3

Kohler¹

2003

Bulletin of the Seismological Society of America

128

133

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“…More than 200 Myr of intense tectonic activity [Burchfiel et al, 1992] has led to a highly heterogeneous crust. At shallow levels (≤2 km depth), the seismic velocities have been observed to vary by more than 50% [Magistrale et al, 2000;Süss and Shaw, 2003]. The most extreme variations, in particular, the deep basins of low-velocity sediments, are controlled by active faulting.…”

Section: Introductionmentioning

confidence: 99%

Full‐3‐D tomography for crustal structure in Southern California based on the scattering‐integral and the adjoint‐wavefield methods

et al. 2014

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We have successfully applied full-3-D tomography (F3DT) based on a combination of the scattering-integral method (SI-F3DT) and the adjoint-wavefield method (AW-F3DT) to iteratively improve a 3-D starting model, the Southern California Earthquake Center (SCEC) Community Velocity Model version 4.0 (CVM-S4). In F3DT, the sensitivity (Fréchet) kernels are computed using numerical solutions of the 3-D elastodynamic equation and the nonlinearity of the structural inversion problem is accounted for through an iterative tomographic navigation process. More than half-a-million misfit measurements made on about 38,000 earthquake seismograms and 12,000 ambient-noise correlagrams have been assimilated into our inversion. After 26 F3DT iterations, synthetic seismograms computed using our latest model, CVM-S4.26, show substantially better fit to observed seismograms at frequencies below 0.2 Hz than those computed using our 3-D starting model CVM-S4 and the other SCEC CVM, CVM-H11.9, which was improved through 16 iterations of AW-F3DT. CVM-S4.26 has revealed strong crustal heterogeneities throughout Southern California, some of which are completely missing in CVM-S4 and CVM-H11.9 but exist in models obtained from previous crustal-scale 2-D active-source refraction tomography models. At shallow depths, our model shows strong correlation with sedimentary basins and reveals velocity contrasts across major mapped strike-slip and dip-slip faults. At middle to lower crustal depths, structural features in our model may provide new insights into regional tectonics. When combined with physics-based seismic hazard analysis tools, we expect our model to provide more accurate estimates of seismic hazards in Southern California.

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“…The shear modulus of sediments is much lower than that of solid rock. For example, Magistrale et al [28] and Hayashi et al [29] compiled shear wave (S-wave) velocities β of sediments within Greater Los Angeles. The properties of the uppermost of these sediments represent the minimum shear modulus of a material that has compacted under gravity.…”

Section: (A) Mechanics Of Tidal Dissipationmentioning

confidence: 99%

“…For accumulated sediments that are buried to approximately 100 m depth, typical values of the S-wave velocity and density are 700 m s −1 and 2300 kg m −3 [28,29], respectively. For these values, the shear modulus is 10 9 Pa and the implied viscosity is 10 13 Pa s.…”

Section: (A) Mechanics Of Tidal Dissipationmentioning

confidence: 99%

Terrestrial aftermath of the Moon-forming impact

Sleep

Zahnle

Lupu

2014

Phil. Trans. R. Soc. A.

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Much of the Earth's mantle was melted in the Moon-forming impact. Gases that were not partially soluble in the melt, such as water and CO 2 , formed a thick, deep atmosphere surrounding the post-impact Earth. This atmosphere was opaque to thermal radiation, allowing heat to escape to space only at the runaway greenhouse threshold of approximately 100 W m −2 . The duration of this runaway greenhouse stage was limited to approximately 10 Myr by the internal energy and tidal heating, ending with a partially crystalline uppermost mantle and a solid deep mantle. At this point, the crust was able to cool efficiently and solidified at the surface. After the condensation of the water ocean, approximately 100 bar of CO 2 remained in the atmosphere, creating a solar-heated greenhouse, while the surface cooled to approximately 500 K. Almost all this CO 2 had to be sequestered by subduction into the mantle by 3.8 Ga, when the geological record indicates the presence of life and hence a habitable environment. The deep CO 2 sequestration into the mantle could be explained by a rapid subduction of the old oceanic crust, such that the top of the crust would remain cold and retain its CO 2 . Kinematically, these episodes would be required to have both fast subduction (and hence seafloor spreading) and old crust. Hadean oceanic crust that formed from hot mantle would have been thicker than modern crust, and therefore only old crust underlain by cool mantle lithosphere could subduct. Once subduction started, the basaltic crust would turn into dense eclogite, increasing the rate of subduction. The rapid subduction would stop when the young partially frozen crust from the rapidly spreading ridge entered the subduction zone.

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The SCEC Southern California Reference Three-Dimensional Seismic Velocity Model Version 2

Cited by 257 publications

References 36 publications

Mantle Heterogeneities and the SCEC Reference Three-Dimensional Seismic Velocity Model Version 3

Mantle Heterogeneities and the SCEC Reference Three-Dimensional Seismic Velocity Model Version 3

Full‐3‐D tomography for crustal structure in Southern California based on the scattering‐integral and the adjoint‐wavefield methods

Terrestrial aftermath of the Moon-forming impact

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