Collaborative Research: Understanding the Spatio-Temporal Characteristics of Earthquakes at Axial Seamount Late in an Eruptive Cycle

DESCRIPTION: Axial Seamount is a hotspot volcano and the most magmatically active feature on the Juan de Fuca oceanic spreading center. The Ocean Observatories Initiative (OOI) cabled observatory at Axial provides a ground-breaking opportunity to capture volcano behavior leading up to, during, and following a seafloor eruption. Axial volcano erupted in 1998 and 2011 and, prior to April 2015, seafloor sensors showed that it was inflating with magma again. Over their first six months of operation, the cabled seismometers at Axial Seamount recorded increasingly high rates of small earthquake activity, supporting the inference that the volcano was in the late stage of its volcanic cycle. This was confirmed in late April 2015 when the volcano erupted. The researchers on this grant will work with both graduate and undergraduate students to analyze this first-ever seafloor volcanic event to be observed in real-time with seafloor sensors. This study will use the OOI cabled ocean bottom seismometer network to determine the pattern of earthquake activity at Axial Seamount to understand how stress at the spreading axis is partitioned spatially and temporally. The implications in terms of possible broad structures of hydrothermal flow will be assessed. Changes in the physical properties of the volcano through a volcanic cycle will be documented, with ultimate aim of advancing knowledge about how individual geologic events sum to produce long-term, steady oceanic spreading. Production of near-real time earthquake catalogs for the continuing OOI cabled seismic data stream will allow rapid identification of significant new events. Relocation analysis will yield relative earthquake locations accurate to within tens of meters, bringing structural features in the seismicity into focus. Focal mechanisms, repeating earthquakes, and shear wave splitting parameters will be obtained to further constrain the volcano's dynamics.