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  • Conference paper
    Emmerton S, Muxworthy AR, Sephton MA, 2013,

    A magnetic solution to the Mupe Bay mystery (poster)

    , IAGA
  • Conference paper
    Emmerton S, Muxworthy AR, Sephton MA, Aldana M, Costanzo-Álvarez V, Bayona G, Williams Wet al., 2013,

    Biodegradation reduces magnetization in oil bearing rocks: magnetization results of a combined chemical and magnetic study (poster)

    , IAGA
  • Conference paper
    Muxworthy AR, Krása D, Williams W, 2013,

    Can PSD grains accurately record the ancient field (invited)

    , IAGA
  • Conference paper
    Almeida T, Muxworthy AR, Williams W, 2013,

    Magnetic characterization of synthetic titanomagnetites

    , IAGA
  • Conference paper
    Almeida T, Muxworthy AR, Wiliams W, Dunin-Borkowski Ret al., 2013,

    Oxidation of pseudo-single domain Fe3O4 particles and associated magnetic response examined by environmental TEM and off-axis electron holography

    , Microscopy and Microanalysis 2013 Annual Meeting
  • Journal article
    Emmerton S, Muxworthy AR, Sephton MA, Aldana M, Costanzo-Alvarez V, Bayona G, Williams Wet al., 2013,

    Correlating biodegradation to magnetization in oil bearing sedimentary rocks

    , GEOCHIMICA ET COSMOCHIMICA ACTA, Vol: 112, Pages: 146-165, ISSN: 0016-7037
  • Conference paper
    Bland PA, Collins GS, Dyl KA, Abreu NM, Davison TM, Ciesla FJ, Muxworthy AR, Moore Jet al., 2013,

    Impact-induced compaction of primordial materials and the effect on the chondrite record.

    , 76th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, Pages: A63-A63, ISSN: 1086-9379
  • Conference paper
    Almeida T, Muxworthy AR, Williams W, Dunin-Borkowski Ret al., 2013,

    Complementary electron energy loss spectroscopy and off-axis electron holography investigation of the chemical remanent magnetisation of synthetic magnetic recorders

    , Electron Microscopy and Analysis Group Conference
  • Conference paper
    Van Ginneken M, Muxworthy A, Genge M, 2013,

    First-Order Reversal Curves (FORC) analysis of micrometeorites

    , 76th Annual Meteoritical Society Meeting
  • Conference paper
    Genge MJ, 2013,

    THE SEPARATION OF METAL DROPLETS FROM MICROMETEORITES: METALLIC RAIN AND THE ORIGINS OF LIFE

    , 76th Annual Meeting of the Meteoritical-Society, Publisher: WILEY-BLACKWELL, Pages: A141-A141, ISSN: 1086-9379
  • Journal article
    Carter JN, Sephton MA, 2013,

    A Bayesian statistical assessment of representative samples for asteroidal or meteoritical material

    , Meteoritics & Planetary Science, Vol: 48, Pages: 976-996, ISSN: 1086-9379

    <jats:title>Abstract</jats:title><jats:p>Primitive substances in asteroid and meteorite materials represent a record of early solar system evolution. To allow the study of these materials, they must be collected and transferred to the laboratory. Collection during sample return missions requires an assessment of the size of samples needed. Meteorite falls or finds must be subdivided into appropriate subsamples for analysis by successive generations of scientists. It is essential, therefore, to determine a representative mass or volume at which the collected or allocated sample is representative of the whole. For the first time, we have used a Bayesian statistical approach and a selected meteorite sample, Murchison, to identify a recommended smallest sample mass that can be used without interferences from sampling bias. Enhancing background knowledge to inform sample selection and analysis is an effective means of increasing the probability of obtaining a positive scientific outcome. The influence of the subdivision mechanism when preparing samples for distribution has also been examined. Assuming a similar size distribution of fragments to that of the Murchison meteorite, cubes can be similarly representative as fragments, but at orders of magnitude smaller sizes. We find that: (1) at all defined probabilities (90%, 95%, and 99%), nanometer‐sized particles (where the axes of a three‐dimensional sample are less that a nanometer in length) are never representative of the whole; (2) at the intermediate and highest defined probabilities (95% and 99%), micrometer‐sized particles are never representative of the whole; and (3) for micrometer‐sized samples, the only sample that is representative of the whole is a cube and then only at a 90% probability. The difference between cubes and fragments becomes less important as sample size increases and any &gt;0.5 mm‐sized sample will be representative of the whole with a probability of 99.9%. The resul

  • Journal article
    Oishi Y, Piggott MD, Maeda T, Kramer SC, Collins GS, Tsushima H, Furumura Tet al., 2013,

    Three-dimensional tsunami propagation simulations using an unstructured mesh finite element model

    , Journal of Geophysical Research: Solid Earth, Vol: 118, Pages: 2998-3018, ISSN: 2169-9313
  • Journal article
    Muxworthy AR, 2013,

    The role of magnetic interactions in natural systems

    , Astronomy & Geophysics, Vol: 54, Pages: 31-35
  • Journal article
    Muxworthy AR, Evans ME, Scourfield S, King JGet al., 2013,

    Paleointensity results from the late-Archaean Modipe gabbro of Botswana

    , Geochemistry Geophysics Geosystems
  • Journal article
    Sephton MA, 2013,

    Aromatic units from the macromolecular material in meteorites: Molecular probes of cosmic environments

    , Geochimica et Cosmochimica Acta, Vol: 107, Pages: 231-241, ISSN: 0016-7037
  • Journal article
    Biggin AJ, Badejo S, Hodgson E, Muxworthy AR, Shaw J, Dekkers MJet al., 2013,

    The effect of cooling rate on the intensity of thermoremanent magnetization (TRM) acquired by assemblages of pseudo-single domain, multidomain and interacting single-domain grains

    , Geophysical Journal International
  • Journal article
    Lappe S-CLL, Feinberg J, Muxworthy A R, Harrison Ret al., 2013,

    Comparison and calibration of non-heating paleointensity methods: A case study using dusty olivine

    , Geochemistry Geophysics Geosystems
  • Conference paper
    Abubakar R, Muxworthy AR, Sephton MA, Fraser Aet al., 2013,

    Experimental investigation of magnetic mineral formation in hydrocarbon environments

    , EGU
  • Journal article
    Gulick S, Christeson G, Barton P, Grieve R, Morgan J, Urrutia Jet al., 2013,

    Geophysical Characterization of the Chicxulub Impact Crater

    , Reviews of Geophysics

    Geophysical data indicate that the 65.5 Ma Chicxulub impact structure is a multi-ring basin, with three sets of semi-continuous, arcuate ring faults and a topographic peak ring. Slump blocks define a terrace zone, which steps down from the inner rim into the annular trough. Fault blocks underlie the peak ring, which exhibits variable relief, due to target asymmetries. The central structural uplift is >10 km and the Moho is displaced by 1-2 km. The working hypothesis for the formation of Chicxulub is: a 50 km radius transient cavity, lined with melt and impact breccia, formed within 10s of seconds of the impact and within minutes, weakened rebounding crust rose kilometers above the surface, the transient crater rim underwent localized deformation and collapsed into large slump blocks, resulting in a inner rim at 70-85 km radius, and outer ring faults at 70-130 km radius. The over-heightened structural uplift collapsed outwards, buried the inner slump blocks, and formed the peak ring. Most of the impact melt was ultimately emplaced as a coherent <3-km thick melt sheet within the central basin that shallows within the inner regions of the peak ring. Smaller pockets of melt flowed into the annular trough. Subsequently, slope collapse, ejecta, ground surge, and tsunami waves infilled the annular trough and annular basin with sediments up to 3 km and 900 m thick, respectively. Testing this working hypothesis requires direct observation of the impactites, within and adjacent to the peak ring and central basin.

  • Journal article
    Warner M, Ratcliffe A, Nangoo T, Morgan J, Umpleby A, Shah N, Vinje V, Stekl I, Guasch L, Win C, Conroy G, Bertrand Aet al., 2013,

    Anisotropic 3D full-waveform inversion

    , Geophysics, Vol: 78, Pages: R59-R80

    We have developed and implemented a robust and practical scheme for anisotropic 3D acoustic full-waveform inversion (FWI). We demonstrate this scheme on a field data set, applying it to a 4C ocean-bottom survey over the Tommeliten Alpha field in the North Sea. This shallow-water data set provides good azimuthal coverage to offsets of 7 km, with reduced coverage to a maximum offset of about 11 km. The reservoir lies at the crest of a high-velocity antiformal chalk section, overlain by about 3000 m of clastics within which a low-velocity gas cloud produces a seismic obscured area. We inverted only the hydrophone data, and we retained free-surface multiples and ghosts within the field data. We invert in six narrow frequency bands, in the range 3 to 6.5 Hz. At each iteration, we selected only a subset of sources, using a different subset at each iteration; this strategy is more efficient than inverting all the data every iteration. Our starting velocity model was obtained using standard PSDM model building including anisotropic reflection tomography, and contained epsilon values as high as 20%. The final FWI velocity model shows a network of shallow high-velocity channels that match similar features in the reflection data. Deeper in the section, the FWI velocity model reveals a sharper and more-intense low-velocity region associated with the gas cloud in which low-velocity fingers match the location of gas-filled faults visible in the reflection data. The resulting velocity model provides a better match to well logs, and better flattens common-image gathers, than does the starting model. Reverse-time migration, using the FWI velocity model, provides significant uplift to the migrated image, simplifying the planform of the reservoir section at depth. The workflows, inversion strategy, and algorithms that we have used have broad application to invert a wide-range of analogous data sets.

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