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1. Investigating Ultra-low Velocity Zones beneath the Southwestern Pacific

   Carson, S.E.; Hansen, S.E.; Garnero, E. (June 2017, Gordon Research Conference)
2. Investigating Ultra-low Velocity Zones beneath the Southwestern Pacific

   Carson, S.E.; Hansen, S.E. (December 2017, American Geophysical Union)
3. Asthenospheric low-velocity zone consistent with globally prevalent partial melting

   https://doi.org/10.1038/s41561-022-01116-9  

   Hua, Junlin; Fischer, Karen M.; Becker, Thorsten W.; Gazel, Esteban; Hirth, Greg (February 2023, Nature Geoscience)

   The asthenosphere plays a fundamental role in present-day plate tectonics as its low viscosity controls how convection in the mantle below it is expressed at the Earth’s surface above. The origin of the asthenosphere, including the role of partial melting in reducing its viscosity and facilitating deformation, remains unclear. Here we analysed receiver-function data from globally distributed seismic stations to image the lower reaches of the asthenospheric low-seismic-velocity zone. We present globally widespread evidence for a positive seismic-velocity gradient at depths of ~150 km, which represents the base of a particularly low-velocity zone within the asthenosphere. This boundary is most commonly detected in regions with elevated upper-mantle temperatures and is best modelled as the base of a partially molten layer. The presence of the boundary showed no correlation with radial seismic anisotropy, which represents accumulated mantle strain, indicating that the inferred partial melt has no substantial effect on the large-scale viscosity of the asthenosphere. These results imply the presence of a globally extensive, partially molten zone embedded within the asthenosphere, but that low asthenospheric viscosity is controlled primarily by gradual pressure and temperature variations with depth. 

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4. Ultra‐Low Velocity Zone Beneath the Atlantic Near St. Helena

   https://doi.org/10.1029/2024GC011559  

   Davison, Felix; Martin, Carl; Parai, Rita; Cottaar, Sanne (July 2024, Geochemistry, Geophysics, Geosystems)

   Abstract There are various hotspots in the Atlantic Ocean, which are underlain by mantle plumes that likely cross the mantle and originate at the core‐mantle boundary. We use teleseismic core‐diffracted shear waves to look for an Ultra‐Low Velocity Zone (ULVZ) at the potential base of central Atlantic mantle plumes. Our data set shows delayed postcursory phases after the core‐diffracted shear waves. The observed patterns are consistent in frequency dependence, delay time, and scatter pattern with those caused by mega‐ULVZs previously modeled elsewhere. Synthetic modeling of a cylindrical structure on the core‐mantle boundary below St. Helena provides a good fit to the data. The preferred model is 600 km across and 20 km high, centered at approximately 15° South, 15° West, and with a 30% S‐wave velocity reduction. Significant uncertainties and trade‐offs do remain to these parameters, but a large ULVZ is needed to explain the data. The location is west of St. Helena and south of Ascension. Helium and neon isotopic systematics observed in samples from this region could point to a less‐outgassed mantle component mixed in with the dominant signature of recycled material. These observations could be explained by a contribution from the Large Low Shear Velocity Province (LLSVP). Tungsten isotopic measurements would be needed to understand whether a contribution from the mega‐ULVZ is also required at St. Helena or Ascension. 

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5. Frequency domain analyses of low-velocity impact loading of elastomeric foams

   https://doi.org/10.1016/j.ymssp.2023.110881  

   Nacy, Somer; Koohbor, Behrad; Youssef, George (December 2023, Mechanical Systems and Signal Processing)