Hazard Notification System (HANS) for Volcanoes
HAWAIIAN VOLCANO OBSERVATORY WEEKLY UPDATE
U.S. Geological Survey
Thursday, September 22, 2022, 5:20 PM HST (Friday, September 23, 2022, 03:20 UTC)
TA'U ISLAND VOLCANO (VNUM #244001)
14°13'48" S 169°27'14" W, Summit Elevation 3054 ft (931 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW
The earthquake swarm related to Taʻū Island continues, with seismicity remaining low over the past week. The position of the earthquake source has not changed. Three earthquakes were reported felt over the past week, with magnitudes similar to larger earthquakes earlier in this swarm. The satellite data from the previous week observed no volcanic activity.
The National Earthquake Information Center (NEIC) will soon start publishing preliminary locations of the largest earthquakes that have occurred during this period of seismic unrest in American Samoa. These locations will appear as dots on a map available at https://earthquake.usgs.gov/earthquakes/map/ and people can report how they feel these events at https://earthquake.usgs.gov/data/dyfi/. However, in the Manuʻa Islands the earthquake locations and depths are currently best-estimates, with large uncertainties resulting from the monitoring network being constrained to the east-west orientation of the islands in American Samoa. Thus, a dot should be viewed as an indication that an earthquake occurred, but it does not provide a precise location. The NEIC will be using standard methods for locating earthquakes and those with poor depth control are given a default depth of 6 miles (10 kilometers). Analysis of the earthquakes in the swarm so far suggests that they occur north of Taʻū Island and the source of the earthquakes has not moved over time. However, due to processing challenges, some preliminary earthquake locations may appear south of Taʻū Island on the NEIC map. The locations of the earthquakes on the NEIC map will change with further refined analyses of the events.
Samoan and English language alert level and color code definitions: (PDF download, 57.68 kb) https://www.usgs.gov/media/files/volcano-aviation-codes-and-alert-levels-english-and-samoan
HVO will continue to issue weekly Taʻū Island updates on Thursdays until further notice. Additional messages will be issued as needed.
FAQ Web Resource
Read our Frequently Asked Questions web page for more information. https://www.usgs.gov/observatories/hvo/frequently-asked-questions-about-earthquakes-american-samoa
It is unclear if this earthquake unrest will escalate to a volcanic eruption and exactly where an eruption might occur. An eruption could pose significant hazards to residents of American Samoa; these hazards include volcanic gases, volcanic ash, low-level localized explosions of lava, lava flows, earthquake shaking, and tsunami. Information about these hazards, which are like those in Hawaii, can be found at this HVO website: https://www.usgs.gov/observatories/hvo/hazards.
The primary hazard of concern at this time is earthquake shaking, although no physically damaging earthquakes have occurred as part of this swarm. For information on how to prepare for an earthquake, see: https://www.usgs.gov/faqs/what-can-i-do-be-prepared-earthquake.
If you feel shaking and are not near the coast, immediately drop, cover, and hold on until the shaking stops. If you are at the coast, heed the natural tsunami warning signs. If you feel a strong or long-duration earthquake, see a sudden rise or fall of the ocean, hear a loud roar from the ocean, or see a large aerial plume from an eruption, a tsunami may follow, and you should immediately move to higher ground. Pacific Tsunami Warning Center: https://tsunami.gov/
Volcanoes in the Manuʻa Islands are monitored with a limited real-time seismic network consisting of four sophisticated seismometers (broadband seismometers)—two on Taʻū Island, one on Ofu Island, and one on Tutuila Island—and eight microseismometers on Tutuila, Taʻū, and Olosega Islands. Two GPS stations provide ground deformation information for Taʻū Island. Satellite remote sensing is another tool being used, which may detect heat, volcanic gas, and volcanic ash associated with early phases of volcanic activity.
Report what you feel and see.
Residents can assist these monitoring efforts by noting and reporting accurate times that they feel earthquake shaking or notice other changes that might be related to volcanic activity to either the Pago Pago National Weather Service Office (https://www.weather.gov/ppg/wsopagooffice) or the American Samoa EOC in Pago Pago (684-699-3800).
American Samoa Volcanoes
Volcanoes in the U.S. Territory of American Samoa are within the area of responsibility of the U.S. Geological Survey’s Hawaiian Volcano Observatory, based in Hilo on the Island of Hawai‘i.
- Taʻū Island website: https://www.usgs.gov/volcanoes/ta-u-island
- Ofu-Olosega website: https://www.usgs.gov/volcanoes/ofu-olosega
NOAA Weather and Tsunami resources
- National Weather Service Pago Pago Office: https://www.weather.gov/ppg/wsopagooffice
- Pacific Tsunami Warning Center: https://tsunami.gov/
- International Tsunami Information Center and American Samoa Tsunami Awareness Information: http://www.tsunamiwave.org
The Hawaiian Volcano Observatory is one of five volcano observatories within the U.S. Geological Survey and is responsible for monitoring volcanoes and earthquakes in Hawaiʻi and American Samoa.
HVO, askHVO@usgs.gov—best contact for regular reporting and questions.
Ken Hon, HVO Scientist in Charge, USGS firstname.lastname@example.org
Natalia Deligne, American Samoa Lead Responding Scientist, USGS email@example.com
Subscribe to these messages: https://volcanoes.usgs.gov/vns2/
Summary of volcanic hazards from eruptions: https://www.usgs.gov/observatories/hvo/hazards
Recent earthquakes in Hawaiʻi (map and list): https://www.usgs.gov/observatories/hvo
Volcanoes of American Samoa: https://www.usgs.gov/observatories/hvo/volcanoes-american-samoa
Explanation of Volcano Alert Levels and Aviation Color Codes: https://www.usgs.gov/programs/VHP/volcanic-alert-levels-characterize-conditions-us-volcanoes