Dispersion of surface waves in the southern Bering Shelf (Bristol Bay) and the Alaska Peninsula is investigated for a study of the regional crustal structure. Our data consist of five shallow earthquakes located along the Aleutian Arc and recorded by long-period, three-component seismographs sited in south-central Alaska. Both Love and Rayleigh group velocities are obtained through the application of the phase-matched filtering technique. The results are converted to equivalent pure-path data by appropriate adjustment using the published information for the continental Alaska.
Treating the shear velocity of each layer as an independent parameter, the pure-path group velocities of Love and Rayleigh waves are jointly inverted in order to obtain a satisfactory agreement between the theoretical and the observed dispersion characteristics. Estimates of the resolving power of the inversion and uncertainty of the final velocity structure show substantial improvement over the previously published models.
With their crustal thicknesses ranging between 33 and 36 km, none of the final models displays structural characteristics reminiscent of an oceanic crust. Over the northernmost path across the Bristol Bay, we found an indication of a weak low-velocity zone (five per cent reduction relative to the lid velocity) whose prominence diminishes towards the south.