Seismic array evidence of a core boundary source for the Hawaiian Linear Volcanic Chain

Abstract

Earthquakes from the Tonga and Samoa islands were used as a source for dT/dΔ determinations at distances of 80°–95°. The data were recorded by two University of Alberta arrays, Vasa and Peace, and three Canadian network seismic stations, EDM, FSJ, and MCC. Earthquakes from Japan, Asia, and South America have small travel time station anomalies and phase velocities that are in agreement with the Jeffreys-Bullen tables. However, events from Tonga and Samoa arrive with phase velocities that are up to 15% higher. The anomaly increases from 0 at 84° to 4 km/sec at 95° at both arrays. The results are not interpretable readily by using anomalous conditions in the downgoing plate in the source region or at the receivers. We conclude that the observations are due to a heterogeneous region of high velocity in the mantle at the core-mantle interface underneath the island of Hawaii.