Major: Geology, Physics
Academic Affiliation: College of William and Mary
Danya’s interest in the geosciences began as an offshoot of a broader interest in environmental justice and water conservation. Recently, her interests have shifted slightly, centering on the applications of remote sensing and other imaging methods to study and analyze the Earth. This summer, Danya worked to characterize the attenuation of Lg phase waves in the Rocky Mountain Central-United States Transition Zone to improve ground motion characterization in the USGS National Seismic Hazard and supplement the attenuation component of the USGS National Crustal Model.
2016- A High Resolution, Local-scale Characterization of Lg Attenuation in the Rocky Mountain–Central United States Transition Zone
Notable regional-scale differences in seismic attenuation exist across the continental United States, and it is well established that the attenuation of Lg-phase waves is greater west of the Rocky Mountains than east of the Rocky Mountains. However, there is considerably less clarity in delineating the boundary or defining the transition in attenuation between the Western U.S. (WUS) and the Central and Eastern US (CEUS). Utilizing Lg-phase waves recorded at regional distances (110-1100 km) at ~400 seismic stations from Nevada to Missouri, we compute the path-averaged apparent quality factor (the inverse of attenuation) Q, source terms, and local amplification factors at a one-octave frequency band centered on 1.0 Hz. Ultimately we produce a high-resolution, local-scale analysis of frequency-dependent Lg attenuation, Q(f), in the Basin and Range, Rocky Mountains, Interior Plains, Colorado Plateau, and Atlantic Plain regions. Additionally, we provide first-order characterizations of the amplification and dampening of seismic waves in each region. Q is a crucial component for modeling the variation of ground motion prediction equations (GMPEs), and our refined Q(f) model will provide valuable insight into local-scale attenuation mechanisms and supplements the attenuation component of the USGS National Crustal Model, which will lead to improved ground motion characterization in the USGS National Seismic Hazard map.
2017- A Laboratory-Scale Analogue Model to Probe Ice Sheet Grounding Line Dynamics
Uncertainty in sea level rise centers on potential mass loss from the Greenland Ice Sheet and West Antarctic Ice Sheet, which can be driven by changes in the grounding line position. Much research into grounding line dynamics has been observational or numerical and only a few efforts have used physical analogue models. Simple analogue models may have the potential to improve our understanding of the grounding line dynamics under idealized and more generalized conditions (i.e. not tied to a specific glaciological regime). Here, we describe a preliminary laboratory scale analogue model to examine grounding line and glacier dynamics. Our model is typified by an oil-based viscous fluid (Re <<1), dispersed on an angled ramp into an inviscid, denser fluid. We used time-lapse photography and measured the velocity, strain, and strain rates and grounding line position and compared our measurements to numerical and analytical models. Further, we can modify our model to simulate particular glaciological regimes to examine the role of ice shelves in stabilizing grounding line positions. Although our experiments are preliminary, future versions can include more complex geometries (e.g., retrograde bed slopes, pinning points and hanging glaciers) to provide insight into the stability of West Antarctica to future changes in ice shelf extent and climate forcing.