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The settling velocity (ws) in estuarine environments can impact whether a region is eroding or accreting sediment on the bed, yet determining this rate can be an indirect process requiring a number of assumptions. Accurate determination of ws is especially needed for numerical models to reproduce observed sediment concentrations at the appropriate timescale. We collected information on suspended sediment flocculation at a channel site (13 m deep) and a shallows site (4 m deep) within South San Francisco Estuary, alongside timeseries of flow, wave statistics, turbulent shear, and bottle samples analyzed for both ws and particle size. Using the measurements of floc size and settling velocity, we performed a sensitivity analysis on the unknown parameters in the general explicit formula for settling velocity. The collected particle size distribution data show that multiple classes of flocs are present; these are characterized as flocculi, microflocs, and macroflocs. We show that ws of flocculi is closest to ws for the full distribution. The determined parameter values lead to near‐bed mass‐weighted settling velocities (standard deviation) of 1.18 (0.55) and 0.22 (0.15) mm/s at the channel and shallows sites, respectively. Modeling efforts can use this work to help select an appropriate sediment model and parameter values. Plain Language Summary: Tides and waves pick up mud on the bottom of estuaries and transport it between the river and ocean or between the shallows and the deep channel. One important control on this transport of mud is how fast it settles out of the water column. Larger things typically settle faster, and as small particles stick together into larger aggregates, or "flocs", the flocs settle faster than the original small particles. We collected data in the channel and shallows of San Francisco Estuary, and compute settling velocity using a range of tuning parameters. We use the observations to narrow the values of these parameters, and we show how the choice of some parameter values can be more important than others in determining settling velocity. In locations where sediment flocculates, this work will help modelers select appropriate models and parameter values. Key Points: The parameters needed to compute settling velocity are constrained using settling column dataMultiple floc classes are common, suggesting a multiple class model is necessaryThe characteristic size of particles in San Francisco Estuary is smaller than the size commonly observed with camera setups [ABSTRACT FROM AUTHOR]

Discusses strategies for teaching problem-solving techniques during an engineering design course in the third year of a four-year degree program. Describes the content of six problem-solving curricular modules, course organization, evaluation and assessment, and results. (Contains 28 references.) (WRM)

The Transportable Array in south-central Alaska spans several subduction zone features: backarc, forearc and volcanic arc, making it an ideal tool to study subduction zone anisotropy. Shear wave splitting analysis of 157 local earthquakes of m b ≥ 3.0 that occurred between 2014 and 2019 yields 210 high-quality measurements at 23 stations. Splitting delay times (δ t) are generally small (δ t ≈ 0.3 s), increasing with distance from the trench. Arc-parallel fast directions, ϕ, are only seen in the forearc, but rotate to arc-perpendicular ϕ in the backarc. Observed ϕ values generally do not parallel teleseismic SKS splitting results, implying that the latter is sensitive primarily to subslab mantle flow, not mantle wedge dynamics. The forearc local-earthquake signal likely originates from anisotropic serpentinite in fractures atop the subducting Pacific Plate, with possible additional signal coming from fractures in the North American crust. Mantle wedge corner flow, potentially with additional arc-perpendicular anisotropy in the subducting slab, explains backarc anisotropy. [ABSTRACT FROM AUTHOR]

Alaska provides an ideal tectonic setting for investigating the interaction between subduction and asthenospheric flow. Within the span of a few hundred kilometers along strike, the geometry of the subducting Pacific plate varies significantly and terminates in a sharp edge. Furthermore, the region documents a transition from subduction along the Aleutian Arc to strike‐slip faulting along the Pacific Northwest. To better understand mantle interactions within this subduction zone, we conduct an SKS shear‐wave splitting analysis on passive‐source seismic data collected between 2011 and 2018 at 239 broadband seismometers, including those from the Transportable Array. Anisotropic fast directions in the east of our study area parallel the Queen Charlotte and Fairweather transform faults, suggesting that the ongoing development of lithospheric anisotropy dominates the results there. However, our observed delay times (δt = 1–1.5 s) obtained across the study region may also imply an asthenospheric contribution to the splitting pattern. Our splitting observations exhibit slab‐parallel fast directions northwest of the trench and a rotation of fast directions around the northeastern slab edge. These observations suggest the presence of toroidal asthenospheric flow around the edge of the downgoing Pacific plate. We suggest that Wrangell Volcanic Field volcanism might be caused by mantle upwelling associated with this flow. Splitting observations closer to the trench can be explained by fossil anisotropy within the downgoing Pacific‐Yakutat plate combined with entrained subslab mantle. The geometry of the slab, including its variable dip and its abrupt eastern edge, thus plays an important role in governing mantle flow beneath Alaska. Key Points: Fast directions parallel major transform faults and Yakutat terrane subduction, suggesting a lithospheric source of anisotropyFast directions wrapping around the slab edge and high delay times suggest a toroidal asthenospheric flow as another cause of anisotropyVariability in slab geometry exerts first‐order control over mantle flow at the edge of the Alaskan margin [ABSTRACT FROM AUTHOR]