On 27 February 2005, one of the largest submarine earthquake sequences ever recorded in 12 years of real-time seismoacoustic monitoring of the northeastern Pacific Ocean occurred at the Juan de Fuca Ridge (JFR) Endeavour segment (Figure 1).
On the basis of available information, an oceanographic expedition was quickly organized to investigate the site for magmatic activity and hydrothermal discharge. The research vessel T.G. Thompson arrived on site and began water column and seafloor surveys just seven days after the onset of earthquake activity, the most rapid response cruise to the JFR yet organized. However, no evidence of plume generation or a seafloor eruption was found.