Hazard Notification System (HANS) for Volcanoes


U.S. Geological Survey
Friday, May 12, 2023, 6:04 AM ChST (Thursday, May 11, 2023, 20:04 UTC)

Report prepared by the U.S. Geological Survey.

No eruptive activity or significant unrest was detected at the Northern Mariana Island volcanoes during the past week. Occasional hydroacoustic events were observed coming from the direction of Ahyi Seamount over the past week, but there have been no satellite observations of  discolored water above the seamount. Hydroacoustic events are signals that show changes in water pressure generated by sound waves in the water. These events can be produced by a number of processes (including underwater volcanic activity) but cannot be precisely located with the available data. When observed in conjunction with discolored water they provide strong evidence of underwater eruptive activity.

Monitoring of Northern Mariana Islands Volcanoes

Northern Mariana Island volcanoes are monitored remotely with satellite data, distant seismic stations in Guam and Chichijima, Japan, and hydroacoustic data from Wake Island. These observations might detect significant explosive activity in the CNMI, but because of the absence of functional local ground-based monitoring stations at the volcanoes, we cannot provide advanced warning of activity.

Ground-based geophysical monitoring data from stations on Anatahan and Sarigan islands have been unavailable since storm damage in August, 2017. In addition, data flow from an intermittently operational seismo-accoustic network on Saipan stopped completely on June 7, 2022. Current logistical challenges in the CNMI prevent visiting these sites to make repairs. A timeline for returning these stations to operation is uncertain. Due to a lack of direct geophysical monitoring on the islands, Anatahan and Sarigan volcano alert levels are designated UNASSIGNED.

Other volcanoes in the CNMI including Farallon de Pajaros, Supply Reef, Maug, Asuncion, Agrigan, Pagan, Almagan, and Guguan are not seismically monitored and are normally designated UNASSIGNED, absent other observations of activity.

For definitions of Aviation Color Codes and Volcano Alert Levels, see: http://volcanoes.usgs.gov/activity/alertsystem/index.php

SUBSCRIBE TO VOLCANO ALERT MESSAGES by email: http://volcanoes.usgs.gov/vns/


CNMI Homeland Security and Emergency Management

USGS Northern Mariana Duty Scientist (907) 786-7497

Satellite information, Washington VAAC