A Seismic Tomography, Gravity, and Flexure Study of the Crust and Upper Mantle Structure of the Emperor Seamounts at Jimmu Guyot

The intraplate Hawaiian-Emperor Seamount Chain has long been considered a hotspot track generated by the motion of the Pacific plate over a deep mantle plume, and an ideal feature therefore for studies of volcanic structure, magma supply, plume-crust interaction, flexural loading, and upper mantle rheology. Despite their importance as a major component of the chain, the Emperor Seamounts have been relatively little studied. In this paper, we present the results of an active-source wide-angle reflection and refraction experiment conducted along an ocean-bottom-seismograph (OBS) line oriented perpendicular to the seamount chain, crossing Jimmu guyot. The tomographic P wave velocity model, using similar to 20,000 travel times from 26 OBSs, suggests that there is a high-velocity (>6.0 km/s) intrusive core within the edifice, and the extrusive-to-intrusive ratio is estimated to be similar to 2.5, indicating that Jimmu was built mainly by extrusive processes. The total volume for magmatic material above the top of the oceanic crust is similar to 5.3 x 10(4) km(3), and the related volume flux is similar to 0.96 m(3)/s during the formation of Jimmu. Under volcanic loading, the similar to 5.3-km-thick oceanic crust is depressed by similar to 3.8 km over a broad region. Using the standard relationships between Vp and density, the velocity model is verified by gravity modeling, and plate flexure modeling indicates an effective elastic thickness (T-e) of similar to 14 km. Finally, we find no evidence for large-scale magmatic underplating beneath the pre-existing crust.

Automated summary

This paper presents results of a study on the Emperor Seamounts, a component of the Hawaiian-Emperor Seamount Chain, using an active-source wide-angle reflection and refraction experiment. The study examines the volcanic structure, magma supply, plume-crust interaction, flexural loading, and upper mantle rheology. The findings suggest that Jimmu guyot, a part of the seamount chain, was mainly built through extrusive processes. Gravity modeling verifies the velocity model, and plate flexure modeling indicates an effective elastic thickness of about 14 km. The study also finds no evidence of large-scale magmatic underplating beneath the pre-existing crust.