Seismic Structure of the Hawaiian Mantle Plume using Array Seismology Methods

Abstract

In this study we apply seismic array methods to infer the depth range of the plume conduit feeding the hotspot of Hawaii. The aim is to detect in real data, the out-of-plane arrivals seen in synthetic plume modelling by Stockmann et al. (2019). However, from the data collected, these arrivals are not reproduced. We suggest that this is more likely to be caused by a combination of mantle heterogeneities interacting with the seismic waves, and an increased effect of wavefront healing at larger plume-receiver distances, rather than by the total absence of a mantle plume underneath Hawaii. For direct waves measured in the Tonga - North America configuration, we found a trend in out-of-plane arrivals opposite to the results of Stockmann et al. (2019). This is not likely to be caused by the plume structure, but might be related to large scale heterogeneities in the lower mantle, for example Ultra Low Velocities Zones or Large Low Shear Velocity Provinces. Furthermore, we observe a consistent negative out-of-plane arrival of three degrees with the seismic network in Alaska for events at different locations. These negative arrivals are probably caused by local crustal and upper mantle heterogeneities, which might be compensated for, using mislocation vectors.