American Samoa is a United States territory which comprises the easternmost islands of a volcanic island chain formed by the Samoan hotspot in the South Pacific Ocean. Its small islands are the tops of volcanoes, and there is an active volcanic seamount nearby. The most recent eruption witnessed by local residents occurred in 1866, and submarine eruptions and earthquakes remind us that this region remains volcanically active.
American Samoa includes Tutuila Island (the main population center), Aunu‘u Island, and the Manu‘a Islands of Ta‘u and Ofu-Olosega about 70 miles to the east. Vailulu‘u Seamount is about 30 miles east of the Manu‘a Islands on top of the Samoan hotspot, where submarine eruptions have occurred several times in the past few decades. Additionally, a near-shore eruption occurred east of Ofu-Olosega in 1866. Away from the Samoan hotspot, large earthquakes, sometimes greater than magnitude 8, can happen along the Tonga Trench, located about 150 miles (240 km) to the southwest of the Samoan archipelago.
An intense swarm of earthquakes was widely felt in the Manu‘a Islands from July 26 to October 2022, which led to an emergency declaration on Aug. 8 by the American Samoa Department of Homeland Security. The NOAA National Weather Service office at Pago Pago and USGS Hawaiian Volcano Observatory deployed staff and resources to the Manu‘a Islands beginning Aug. 13.
Prior to the swarm, American Samoa had no local earthquake monitoring, and the closest station was in the Independent State of Samoa, located about 150 miles (250 km) to the west of the Manu‘a Islands. HVO and NWS staff rapidly deployed local seismic sensors in the Manu‘a and Tutuila Islands, which revealed that hundreds of earthquakes per day were occurring about 10–15 miles (16–24 km) north of Ta‘u Island. The data also showed that, along with the intense earthquake activity, molten magma was likely migrating into the area. Fortunately, the number and size of earthquakes declined significantly after August, ending the crisis.
In the three years since, HVO and the USGS earthquake hazards program continue to actively assess the region for local volcanic and earthquake activity.
All volcanoes in American Samoa are currently at USGS Volcano Alert Level/Aviation Color Code NORMAL/GREEN, meaning that these volcanoes are in background/non-eruptive states. Regionally, however, the Tonga Trench continues to produce numerous earthquakes, as is common for subduction zones. A recent example occurred on Aug. 18, 2025, when a magnitude 5.5 earthquake was observed and located by the USGS.
In collaboration with NWS, HVO went to the Manu‘an Islands for joint outreach with the villages of Olosega, Ofu, Ta‘u, Faleasao, and Fiti‘uta. Here, they met with teachers and community leaders to share information about the volcanoes of American Samoa; NWS shared information about tsunami, hurricanes, and other weather and marine hazards.
Between community meetings, they maintained and improved the monitoring network. There were two major initiatives.
The first was getting a broadband seismic station — the gold standard for earthquake and volcano monitoring — back online in eastern Ta‘u.
Unfortunately, in the past year, rapid vegetation growth covered the solar panels used to power the station. As a result, no data had been received for several months (thankfully, the network had enough working stations to be able to continue monitoring). A work party of HVO, NWS, American Samoa’s Territorial Emergency Management Coordination Office, and local residents removed vegetation from the site, allowing the station to provide service to the community once again. The loan of tools was greatly appreciated!
The second initiative was to replace sensors or install other new seismometers, used to supplement the broadband network. HVO thanks the American Samoan Department of Education, the Department of Homeland Security, ASTCA, and a handful of Manu‘a residents for hosting these seismometers.
After a successful trip to the Manu‘a Islands, HVO staff returned to Tutuila for further outreach, including attending the 4th Annual Disaster Resilience Summit. HVO plans to be back next year for another round of monitoring network maintenance, strengthening partnerships, and continuing to serve the people of American Samoa.
If you want to learn more about earthquake and volcano monitoring in American Samoa, please see this webpage: https://tinyurl.com/vueth235.
Volcano activity updates
Kilauea has been erupting episodically within the summit caldera since Dec. 23, 2024. Its USGS Volcano Alert level is WATCH.
Spattering and flames are putting on a show from the north vent. Many periods of precursory overflows have occurred since 8:38 AM HST this morning marking the start of intermittent precursory eruptive activity of episode 33. No unusual activity has been noted along Kilauea’s East Rift Zone or Southwest Rift Zone.
Mauna Loa is not erupting. Its USGS Volcano Alert Level is at NORMAL.
Two earthquakes were reported felt in the Hawaiian Islands during the past week: A magnitude-2.9 earthquake 4 km (2 mi) SW of Kahaluu-Keauhou at 4 km (2 mi) depth occurred on September, 15, 2025 at 09:49. A magnitude-3.1 earthquake 14 km (8 mi) SE of Fern Forest at 9 km (5 mi) depth occurred on September, 13, 2025 at 03:01.
Please visit HVO’s website for past Volcano Watch articles, Kilauea and Mauna Loa updates, volcano photos, maps, recent earthquake information, and more. Email questions to askHVO@usgs.gov.