No records exist of previous activity in the area. RSP stations recorded seismic activity from Monowai in April 1977, January 1980, May 1982, and June 1986. A strong sulfur smell was noted but no bubbles were visible. A minimum depth of 100 m was measured. Two vertical plumes extended to the surface.
Depths are in meters.
Courtesy of the Defence Scientific Establishment. The signals originated in the vicinity of Monowai Seamount. The swarm was located at 25.92 S, 177.15 W, essentially the coordinates of the Monowai seamount. The T-wave swarm consisted of four episodes. The first, at 1751 on 27 November, lasted for 20 minutes and included seven separate explosions and other strong events.