Seismic Tomography

doi:10.1007/978-94-009-3899-1

Cited by 195 publications

(1 citation statement)

References 119 publications

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“…Of course, large amounts of data are not new to the Earth sciences, and, with respect to volume, many Earth history and geochemistry compilations are small in comparison to the datasets used in other subdisciplines, including seismology (e.g., Nolet, 2012), climate science (e.g., Faghmous and Kumar, 2014), and hydrology (e.g., Chen and Wang, 2018). As a result, many Earth history compilations likely do not meet the criteria to be called "big data," which is a term that describes very large amounts of information that accumulate rapidly and which are heterogeneous and unstructured in form (Gandomi and Haider, 2015; or "if it fits in memory, it is small data").…”

Section: Introductionmentioning

confidence: 99%

Curation and Analysis of Global Sedimentary Geochemical Data to Inform Earth History

Mehra¹,

Keller²,

Zhang³

et al. 2021

GSAT

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Large datasets increasingly provide critical insights into crustal and surface processes on Earth. These data come in the form of published and contributed observations, which often include associated metadata. Even in the best-case scenario of a carefully curated dataset, it may be nontrivial to extract meaningful analyses from such compilations, and choices made with respect to filtering, resampling, and averaging can affect the resulting trends and any interpretation(s) thereof. As a result, a thorough understanding of how to digest, process, and analyze large data compilations is required. Here, we present a generalizable workflow developed using the Sedimentary Geochemistry and Paleoenvironments Project database. We demonstrate the effects of filtering and weighted resampling on Al 2 O 3 and U contents, two representative geochemical components of interest in sedimentary geochemistry (one major and one trace element, respectively). Through our analyses, we highlight several methodological challenges in a "bigger data" approach to Earth science. We suggest that, with slight modifications to our workflow, researchers can confidently use large collections of observations to gain new insights into processes that have shaped Earth's crustal and surface environments. 1 Supplemental Material: table of valid lithologies; map depicting sample locations; crossplot illustrating analytical uncertainty; flowchart of the proposed workflow; histograms showing the effects of progressive filtering, the distribution of spatial and age scales, and proximity and probability values; and results of sensitivity tests.

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Section: Introductionmentioning

confidence: 99%

Curation and Analysis of Global Sedimentary Geochemical Data to Inform Earth History

Mehra¹,

Keller²,

Zhang³

et al. 2021

GSAT

View full text Add to dashboard Cite

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Three‐dimensional shallow structure from high‐frequency ambient noise tomography: New results for the Mygdonia basin‐Euroseistest area, northern Greece

et al. 2014

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We examine the use of ambient noise cross‐correlation tomography for shallow site characterization using a modified two‐step approach. Initially, we extract Rayleigh wave traveltimes from correlation traces of vertical component seismic recordings from a local network installed in Mygdonia basin, northern Greece. The obtained Rayleigh wave traveltimes show significant spatial variability, as well as distance and frequency dependence due to the 3‐D structure of the area, dispersion, and anelastic attenuation effects. The traveltime data sets are inverted through a surface wave tomography approach to determine group velocity maps for each frequency. The proposed tomographic inversion involves the use of approximate Fresnel volumes and interfrequency smoothing constraints to stabilize the results. In the last step, we determine a final 3‐D velocity model using a node‐based Monte Carlo 1‐D dispersion curve inversion. The reliability of the final 3‐D velocity model is examined by spatial and depth resolution analysis, as well as by inversion for different model parameterizations. The obtained results are in very good agreement with previous findings from seismic and other geophysical methods. The new 3‐D VS model provides additional structural constraints for the shallow sediments and bedrock structure of the northern Mygdonia basin up to the depth of ∼200–250 m. Present work results suggest that the migration of ambient tomography techniques from large scales (tens or hundreds of km) to local scales (few hundred meters) is possible but cannot be used as a black box technique for 3‐D modeling and detailed geotechnical site characterization.

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Anisotropic tomography of Hokkaido reveals delamination‐induced flow above a subducting slab

et al. 2015

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We present a new 3-D anisotropic seismic model for the crust and upper mantle beneath Hokkaido (Japan) based on tomographic inversion of P and S arrival times from a regional seismic database. The P model is parameterized with three parameters at each point that describe the azimuthal anisotropy; the S model is represented isotropically. The isotropic P and S velocity anomalies match nearly perfectly. In the crust, they show a prominent linear anomaly in central Hokkaido along the Kamuikotan and Hidaka Belts, which represents the area of eastward underthrusting of the Japan Block underneath the Kuril fore arc. We interpret the high-velocity anomaly beneath the Hidaka zone as being delaminated mafic crust and entrained mantle lithosphere, which developed due to crustal shortening in the collision zone. One of our vertical sections shows a very unusual configuration for a subduction zone: a low-velocity slab is overlain by a high-velocity body in the mantle wedge. We propose that the high-velocity delaminated material sinking along the slab surface prevents the escape of fluids and melts from the upper part of the slab, where they are generated due to phase transitions. As a result, a large portion of the fluids is entrained downward and lowers the seismic velocities in the slab. The azimuthal anisotropy in the crust clearly corresponds to the major tectonic units and delineates the major suture zones. In the mantle, the anisotropy has a fan-shaped configuration and most likely represents the deviating of flows starting in southern Hokkaido and splitting into three directions. The western and eastern flows proceed toward the two volcanic groups on Hokkaido, and they may carry with them additional material to trigger the characteristic caldera-forming eruptions in these groups.

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Seismic Tomography

Cited by 195 publications

References 119 publications

Curation and Analysis of Global Sedimentary Geochemical Data to Inform Earth History

Curation and Analysis of Global Sedimentary Geochemical Data to Inform Earth History

Three‐dimensional shallow structure from high‐frequency ambient noise tomography: New results for the Mygdonia basin‐Euroseistest area, northern Greece

Anisotropic tomography of Hokkaido reveals delamination‐induced flow above a subducting slab

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