Seismicity and velocity structure of Loihi seamount from the 1996 earthquake swarm

The largest earthquake swan yet recorded on Loihi submarine volcano took pl ace in July and August of 1996. The swarm consisted of two phases of seismi c activity and was associated with the formation of a pit crater and additi onal faulting of Loihi's summit platform. The first phase of activity was c omprised of predominantly high-frequency events scattered over the southern flanks of the volcano. Following a day of seismic quiescence, the second p hase of activity began, consisting of lower-frequency earthquakes with stro ng T-phases. The phase 2 events took place beneath Loihi's summit, presumab ly marking the formation of the pit crater, Pele's Pit. Data obtained by an ocean-bottom seismometer (OBS) on Loihi during the swarm help constrain a new velocity model for Loihi. The relocated earthquakes, combined with othe r characteristics of the swarm, enabled us to develop a model for the event s leading up to the formation of Pele's Pit that includes (I) a prolonged e ruption, (2) a tectonic event beneath Loihi's south flank, and (3) the drai nage of a shallow magma chamber.