Mantle Transition Zone Receiver Functions for Bermuda: Automation, Quality Control, and Interpretation

The origin of the Bermuda rise remains ambiguous, despite, or perhaps because of, the existence of sometimes incongruous seismic wave-speed and discontinuity models in the sub-Bermudian mantle. Hence, whether Bermuda is the surface manifestation of a mantle plume remains in question. Using the largest data set of seismic records from Bermuda to date, we estimate radial receiver functions at the Global Seismographic Network station BBSR in multiple frequency bands, using iterative time-domain deconvolution. Motivated by synthetic experiments using axisymmetric spectral-element forward waveform modeling, we devise a quality metric for our receiver functions to aid in the automation and reproduction of mantle transition zone discontinuity studies. We interpret the complex signals we observe by considering the mineralogical controls on mantle transition zone discontinuity structure, and conclude that our results are likely to be indicative of a thicker than average mantle transition zone. Our result is incompatible with the canonical model of a whole mantle plume in an olivine dominated mantle; however, considerations of phase transitions in the garnet system would allow us to reconcile our observations with the possible presence of a through-going hot thermal anomaly beneath Bermuda.