Investigating the seismic structure and visibility of dynamic plume models

Despite the fact that mantle plumes may play a major role in the transport of heat and mass through the Earth, their possible origin and thermochemical structure still fuels many debates. Here, geodynamic modelling and mineral physics data are combined to calculate the
3-D seismic structure of two different thermochemical plume models. We use these models to perform a full-waveform simulation, sending seismic waves through the plumes, in order to generate synthetic seismograms. We then analyse the seismograms with array methods to investigate potential seismic scattering from the plumes. Using velocity spectral analysis and slowness-backazimuth plots, we do not detect scattering. However at longer dominant periods (25 seconds) we see several out-of-plane arrivals that are consistent with an apparent bending of the wavefront around the plume conduit. At shorter periods (15 seconds) these arrivals are no longer visible. We also detect reflections off the dense chemical pile at the base of the mantle which serves as the plume source. Our results indicate that observation of plume-like structures in real data may be achieved by considering waves travelling in all directions and over a range of periods