Ahyi volcano (Mariana Islands, USA) - Smithsonian / USGS Weekly Volcanic Activity Report for 23 April-29 April 2014 (New Activity / Unrest)

Seismic stations on Pagan, Sarigan, Anatahan, and Saipan began recording signals starting at 0635 on 24 April believed to be from an undersea volcanic source. Hydroacoustic sensors on Wake Island suggested that the source is at or near Ahyi seamount, although it was possible that the vent is located at one of the other volcanic seamounts in the area. While conducting coral reef research at Farallon de Pajaros, NOAA divers reported hearing loud explosions and feeling the shock waves.
One of the more powerful explosions was felt by the crew as it reverberated through the hull of the ship. On 27 April the Color Code was raised from Unassigned to Yellow. A report issued at 0536 on 30 April noted that seismic activity remained high.

Sources: Emergency Management Office of the Commonwealth of the Mariana Islands and United States Geological Survey Volcano Hazards Program, Bill Chadwick, Oregon State University's Marine Science Center and NOAA/PMEL EOI Program, personal communication
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From: Global Volcanism Program, 2014. Report on Ahyi. In: Mayberry, G (ed.), Weekly Volcanic Activity Report 23 April-29 April 2014. Smithsonian Institution and US Geological Survey.