HR: 0830h
AN: V51A-04    [Abstracts]
TI: Upper mantle seismic structure beneath the Azores hotspot from finite frequency tomography
AU: shen, y
EM: yshen@gso.uri.edu
AF: University of Rhode Island, South Ferry Road, Narragansett, RI 02882 United States
AB: The Azores archipelago represents one of the classic hotspots that interact with the mid-ocean ridges. While geochemical studies have provided clear evidence for chemical anomalies in the mantle from basalts collected on the islands and at the adjacent mid-Atlantic ridge, the seismic structure beneath Azores has never been imaged directly at regional and local scales. In this study, we construct the first high-resolution seismic velocity models of the mantle structure beneath the hotspot from teleseismic body waves recorded by seismic stations on the Azores islands. Unlike in conventional tomography based on ray theory, the three-dimensional sensitivity kernels of body wave travel times are used to account for wave front healing, scattering, and other diffraction effects of realistic seismic waves. The results from ~150 P wave relative travel times show a pronounced low velocity anomaly in the shallow mantle (~100 km depth) along the Azores islands. The low velocity anomaly becomes elongated in the NE-SW direction at greater depth (100-200 km). The model shows a columnar low-velocity anomaly that extends from 200 km to 400 km depth northeast of Terceira. These results are consistent with geochemical observations and provide seismic evidence for the proposed mantle plume-ridge interaction model, in which the plume conduit bends toward Azores triple junctions, supplying melt along a lateral sublithospheric channel.
DE: 1025 Composition of the mantle
DE: 1040 Isotopic composition/chemistry
DE: 7218 Lithosphere and upper mantle
DE: 8121 Dynamics, convection currents and mantle plumes
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2005 Joint Assembly