Upper mantle structure beneath the Society hotspot and surrounding region using broadband data from ocean floor and islands

We determined the three-dimensional shear wave velocity structure beneath the South Pacific superswell down to a depth of 200 km by analyzing fundamental Rayleigh wave records from permanent and temporary land-based and seafloor seismometers in the Pacific Ocean. Data from the Tomographic Investigation by seafloor ARray Experiment for the Society hotspot (TIARES) project yield excellent spatial resolution of velocity anomalies in the central part of the superswell, near the Society hotspot. Localized slow anomalies are found near hotspots in the upper mantle, but the vertical profiles of the anomalies vary from location to location: Slow anomalies near the Samoa, Macdonald, Pitcairn, and Society hotspots extend to at least 200 km depth, while a slow anomaly near the Marquesas hotspot extends only to ~150 km depth. Owing to the recently deployed seafloor array, horizontal resolutions of slow anomalies near the Society hotspot are substantially improved: The slow anomalies are about 300 km in lateral extent and have velocity anomalies as low as −6 %. The lithosphere thickness is estimated to be ~70 km in the vicinity of all hotspots, which may indicate thermal erosion by mantle plumes.