Using the highest-resolution and longest-period Love wave phase velocity maps that have been developed for the Continental U.S., we are investigating regional variations in Radial anisotropy in the upper mantle.
The track of the iceland hotspot across Greenland remains a -somewhat- open question in seismology. Using P-s converted phases, we are measuring the thickness of the mantle transition zone across Greenland,
and inferring its temperature. This allows us to chart the path of the iceland plume, as well as develop a more broader understanding of plume-transition zone interactions. This is the first study to measure transition zone thickness in Greenland.
Our inferences of the properties of Earth structure are guided by tomographic models of Earth structure. Reconciling global and regional tomographic models is necessary to
understand the spectra of the Earth's heterogeneity across scales and constrain geodynamic processes across vast length and timescales. This reconciliation has previously been impeded
by the different basis functions one must use to decompose global and regional models, which impede a true comparison. Comparison via the simple truncation of a global model is equivalent to convolution with
a boxcar function, resulting in oscillations when expanded into the wavenumber domain. To avert this, we use wavelets to spatiospectrally localize regional and global models,
allowing for a true and formal comparison. This expands our ability to analyse mantle heterogeneity, allowing us to develop spatially-varying maps of agreement between global models,
chimeric models taking advantage of the best-constrained spectral ranges from global and regional models, and a full comparison of model correlation and RMS over select geographical regions such as the Continental US, which takes advantage of the
impressive resolution offered by recent seismic deployments.
Codes to enable anyone to analyse a range of tomographic models using this framework within the Python environment will soon be released to the public.
This project started as part of an IRIS Internship during my undergraduate years. My blog during this time is hosted here: https://www.iris.edu/hq/internship/blogs/user/163
We are using shear-wave splitting of teleseismic SKS phases to characterize mantle deformation beneath greenland, taking advantage of sophisticated methods to analyze the large parameter space and constrain depth-dependent anisotropy in the region. We explore the origins of depth-dependent anisotropy in the context of the region's tectonic history.
We showed for the first time that measurements of Rayleigh wave phase and amplitude (and phase velocity) are affected by interference from major-arc overtones- the interference is best seen at epicentral distances greater than 120 degrees.
Empirical proof of the phenomenon, through analysis of measurements made on spectral-element simulations and real data recorded by USArray, is shown in our manuscript here.
We have more generally explored the phenomenon of overtone interference rigorously, with the goal of better understanding the origin of aspects of the interference pattern
and the extent to which different factors effect it. We have shown that the relative excitation of different overtones can prove to be a powerful predictor of the strength of interference, and can explain the distribution of error in Rayleigh wave phase velocities as a function of epicentral distance.
In a study in GJI , we showed that considering the relative excitation of overtones and the FM, as well as the relative group and phase velocities of the overtones and FM, can explain well the location, amplitude, and wavelength of interference.
We were able to leverage variations in path-integrated group velocities to conduct Love-wave tomography of the United States, as is shown in a study in GRL here.
We are currently extending our understanding of overtone interference to examine the extent to which it may be present on other planetary bodies with current or future planned seismometer presence (e.g. The Earth's Moon, Mars, Venus, and Titan)
Understanding the properties of hydrated mineral phases at depth can yield powerful insight into the bulk properties of Earth structure in geodynamically complex settings such as the hydrated layers overlying subducting slabs. Using first-principle ab initio simulations of crystal structure allows us to model the equations of state, detailed crystal structure, and elasticity of these phases. The latter observation also allows us to understand the anisotropy of these phases. Results from these studies were published here and here. I was supervised by Professor Mainak Mookherjee during the course of this work.