Wright Vanshan

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Last Name
Wright
First Name
Vanshan
ORCID
0000-0002-3238-4526

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  • Article
    Microstructural differences between naturally-deposited and laboratory beach sands
    (Springer, 2021-11-11) Ferrick, Amy ; Wright, Vanshan ; Manga, Michael ; Sitar, Nicholas
    The orientation of, and contacts between, grains of sand reflect the processes that deposit the sands. Grain orientation and contact geometry also influence mechanical properties. Quantifying and understanding sand microstructure thus provide an opportunity to understand depositional processes better and connect microstructure and macroscopic properties. Using x-ray computed microtomography, we compare the microstructure of naturally-deposited beach sands and laboratory sands created by air pluviation in which samples are formed by raining sand grains into a container. We find that naturally-deposited sands have a narrower distribution of coordination number (i.e., the number of grains in contact) and a broader distribution of grain orientations than pluviated sands. The naturally-deposited sand grains orient inclined to the horizontal, and the pluviated sand grains orient horizontally. We explain the microstructural differences between the two different depositional methods by flowing water at beaches that re-positions and reorients grains initially deposited in unstable grain configurations.
  • Article
    No cryosphere-confined aquifer below InSight on Mars
    (American Geophysical Union, 2021-04-11) Manga, Michael ; Wright, Vanshan
    The seismometer deployed by the InSight lander measured the seismic velocity of the Martian crust. We use a rock physics model to interpret those velocities and constrain hydrogeological properties. The seismic velocity of the upper ∼10 km is too low to be ice-saturated. Hence there is no cryosphere that confines deeper aquifers and possibly no aquifers locally. An increase in seismic velocity at depths of ∼10 km could be explained by a few volume percent of mineral cement (1%–5%) in pore space and may document the past depth of aquifers.
  • Article
    The effects of 180 years of aging on the physical and seismic properties of partially saturated sands
    (American Geophysical Union, 2021-05-10) Wright, Vanshan ; Hornbach, Matthew J.
    Constraining how the physical properties and seismic responses of recently deposited sands change with time is important for understanding earthquake site response, subsurface fluid flow, and early stages of lithification. Currently, however, there is no detailed (cm-scale) assessment of how sand's physical properties and associated seismic velocities evolve over the first two centuries after deposition. Here, we integrate sedimentation rates with seismic velocity and sediment physical properties data to assess how the vadose zone sands at Port Royal Beach, Jamaica, change within 180 years after deposition. We show that compressional and shear wave velocities increase with sediment age, whereas porosity, grain size, sorting, mineralogy, and cementation fraction remain relatively unchanged during the same period. Rock physics models (constrained by the measured physical properties) predict constant seismic velocities at all sites regardless of sediment age, though misfits between modeled and observed velocities increase with sediment age. We explain these misfits by proposing that shallow sands undergo microstructural grain reorganization that leads to a more uniform distribution of grain contact forces with time. Our results imply that beach sands undergo a previously undocumented lithification process that occurs before compaction.
  • Article
    Strategies for and barriers to collaboratively developing anti‐racist policies and resources as described by geoscientists of color participating in the unlearning racism in Geoscience (URGE) program
    (American Geophysical Union, 2023-02-17) Burton, Carlene ; Duran, Gabriel ; Wright, Vashan ; Chmiel, Rebecca
    The Unlearning Racism in Geosciences (URGE) program guides groups of geoscientists as they draft, implement, and assess anti‐racist policies and resources for their workplace. Some participating Geoscientists of Color (GoC) shared concerns about microaggression, tokenism, and power struggles within their groups. These reports led us to collect and analyze data that describe the experiences of GoC in URGE. The data are from five discussion groups and two surveys. Our analyses revealed that participating GoC want to continue working with White colleagues on anti‐racist work. GoC want White colleagues not to shy away from doing anti‐racist work. Instead, GoC want White colleagues (a) to create and adhere to robust behavioral codes of conduct, (b) to focus discussions on anti‐racism, (c) to act on anti‐racism initiatives, (d) not to prompt GoC to educate them or reveal trauma, and (e) to refrain from microaggressions and tokenism. These desired outcomes were achieved in some groups with varying degrees of success. Correcting a history of mistrust relating to racism and anti‐racism action is key to implementing and assessing effective anti‐racist policies and resources. This requires leadership support, following through on anti‐racism action, and deepening relationships between GoC and White colleagues. Future anti‐racist programs should spend a substantial amount of time on and demonstrate the importance of training participants how to discuss racism effectively and how to create and adhere to robust behavioral codes of conduct. Future programs should also explore developing a robust program‐wide code of conduct that includes a policy for reporting offenses.