Flexure and seismicity beneath the south flank of Kilauea Volcano and tectonic implications

Abstract

We present a refined model for the tectonic behavior of Kilauea volcano's south flank, including flexure calculations and microearthquake data supportive of the model. In our model the south flank moves seaward over the downwardly flexed ocean crust in a manner analogous to an accretionary prism in a subduction zone. The flank is driven seaward by the gravitational stresses inherent in its shape; this driving force is augmented by high‐density material in Kilauea's rift zones. Elastic flexure calculations predict a configuration for the downwardly flexed crust which agrees with previous seismic refraction and gravity modeling. This configuration in turn is consistent with the hypothesis that many earthquakes occur along the volcanic pile/ocean crust interface. Focal mechanisms for these events predominantly indicate southeastward directed overthrusting. We also propose a relationship between rift zone intrusion and south flank displacement, including a suggestion that the decollement configuration controls the relative activity of Kilauea's east and southwest rift zones.