New insights into geohazard risks in Jamaica, Haiti, and the Dominican Republic: A compendium of recent GeoscientistswithoutBorders results

The Effects of 180 years of Aging on the Physical and Seismic Properties of Partially Saturated Sands

“…Since the microstructure of shallow sands in the upper 2-12 meters controls subsurface fluid flow, shear strength, and thus resistance to earthquake-triggered liquefaction (e.g., Martin et al, 1975), an implication of our study is that contact-creep is more dominant than porosity-reducing mechanical compaction at controlling liquefaction. Lastly, we predict that our main findings are likely replicable at other Holocene beaches because Port Royal Beach's porosities, bulk densities, grain sizes, and coastline progradation rates (Figure S1) are similar to other Holocene beaches across the world (Atkins & McBride, 1992;Gunn et al, 2006;McDonald, 2013;McLean & Kirk, 1969;Prodger et al, 2016;Pryor, 1973).…”

“…We perform a cm‐scale assessment of how vadose zone sands (upper 2.2 m) at Port Royal Beach, Jamaica, change within 180 years after deposition. This prograding beach is scientifically appropriate for our study because the beach's sediment deposition, erosion, and liquefaction histories are well‐documented, and there exist legacy maps for constraining sediment age at decadal resolutions (Fuller, 1907; Goreau & Burke, 1966; McDonald et al., 2013). We interpret that its sands experience grain reorganization (i.e., rolling, slipping, and rotation) that leads to changes in grain positions and contact geometries, which then lead to more uniform distributions of contact forces but no significant changes to porosity.…”

The effects of 180 years of aging on the physical and seismic properties of partially saturated sands

“…Since the microstructure of shallow sands control subsurface fluid flow and resistance to earthquake-triggered slope instability, an implication of our study is that contact-creep is more dominant than porosity-reducing mechanical compaction at controlling slope stability. Lastly, we predict that our main findings are likely replicable at other Holocene beaches because Port Royal Beach's porosities, densities, grain sizes, and coastline progradation rates (Figure S1) are similar to other Holocene beaches across the world (McLean & Kirk, 1969;Pryor 1973;Atkin & McBride, 1992;Gunn et al, 2006;Prodger et al, 2016;McDonald, 2013).…”

“…We perform a cm-scale assessment of how vadose zone sands (upper 2.2 m) at Port Royal Beach, Jamaica, change within 180 years after deposition. This prograding beach is scientifically appropriate for our study because the beach's sediment deposition, erosion, and liquefaction history are well-documented, and there exist legacy maps for constraining sediment age at decadal resolutions (Fuller, 1907;Goreau & Burke, 1966;McDonald et al, 2013). We interpret that its sands experience grain reorganization (i.e., rolling, slipping, and rotation that leads to changes in grain positions and contact geometries) that leads to more uniform distributions of contact forces but no significant changes to porosity.…”