Dense core flexure modeling at the Louisville Seamount Chain

Abstract

The flexural response of the oceanic lithosphere to long-term geological loads (e.g., seamounts and ocean islands) has been effectively approximated using elastic plate model. The flexural rigidity to support a given load depends on the effective elastic thickness of the oceanic lithosphere, Te. Therefore, the flexural response can be quantified simply by Te when the shape and mass of volcanic loads are specified. As for flexure modeling at seamounts, the density structure of a seamount needs to be approximated properly in order to estimate the amount of the driving force resulting from the given volcanic construct. Here we utilize the dense core model for the seamount density structure, which divides a seamount body into the inner dense core, outer volcanic edifice, and peripheral sedimentary layers based on the seismically imaged inner structures of seamounts. In this study, we conduct three- dimensional flexure modeling with dense core at the 14 seamounts of Louisville Seamount Chain (LSC) located on the Pacific Plate. The five older seamounts of the LSC are situated on the oceanic crust produced from the Osbourn Trough (OT), which were active during the Cretaceous normal superchron. These northwestern seamounts of the LSC are categorized as the OT group, whereas the five younger seamounts (southeastern ones of the LSC) are named as the PA group as they are located on the Pacific Plate. The four seamounts between these groups are positioned between the East and West Wishbone Scarps, which are suggested as the eastern margin of the seafloor spread from the OT. Because the seafloor age beneath these seamounts has not been resolved by magnetic anomalies, we categorized them as the Q group. From the flexure modeling, the Te estimates of the LSC are in the range of 6 to 8 km for the OT group, 6 to 28 km for the Q group, and 4 to 12 km for the PA group. Comparison of the Te estimates with the age of the plate at the time of formation, we find the Te estimates from both