Rayleigh-wave dispersion along the Hawaiian Swell: A test of lithospheric thinning by thermal rejuvenation at a hotspot

Abstract

In this paper we present a seismological test of the 'thermal rejuvenation' model for the formation of the Hawaiian Swell, the archetype of a midplate hotspot swell. Twostation measurements of Rayleigh-wave group and phase velocities between Midway Atoll and O'ahu provide the basis for the test: comparison of the observed dispersion curves with age-dependent, regionalized dispersion curves suggests that the swell has the seismic velocity structure of 50-110Myr old lithosphere rather than that of 20-50 Myr old lithosphere as suggested by the rejuvenation model. Joint inversion of the group- and phase-velocity curves for isotropic velocity models yields an estimate of ~ 100 km for the seismic lithosphere's thickness along the swell. This value is difficult to reconcile with the 40-50 km thickness demanded by the rejuvenation model. Preliminary measurements of the coefficients of anelastic attenuation are also presented. Although the accuracy of these values is difficult to assess, they too appear to be consistent with thick lithosphere.