The earthquake swarm occurring in the Manuʻa Islands of American Samoa has been designated by the U.S. Geological Survey Hawaiian Volcano Observatory (HVO).
The federal entity responsible for monitoring earthquakes and volcanoes in American Samoa has assigned the Taʻū Island and Ofu-Olosega Volcano Alert Levels to ADVISORY and Aviation Color Codes YELLOW.
The designation previously was UNASSIGNED.
“This designation does not reflect a change in the behaviour of either volcano; it simply acknowledges that the number, size, and frequency of earthquakes being felt by people on Taʻū Island and Ofu-Olosega are well above typical background activity (a NORMAL/GREEN alert level).”
Current earthquake monitoring is based on the number and relative size of earthquakes and the estimated distance of earthquakes from the microseismometers. Due to the limitations of the current earthquake monitoring equipment, the exact location, depth, and magnitude of these earthquakes remains unknown.
The first reports of felt earthquakes occurred on July 26, 2022. Personal reports and instruments installed over the past week confirm the continuation of elevated earthquake activity.
Data analysis from simple earthquake detection equipment installed on Tutuila, Taʻū, and Ofu-Olosega Islands indicate that the earthquakes are occurring beneath or around the Manuʻa Islands, likely closer to Taʻū rather than Ofu-Olosega.
Approximately 20 earthquakes per hour have been recorded for the past several days in the Manuʻa Islands. Estimated magnitudes of the largest earthquakes are between magnitude 2 and 3. The USGS will have more information about the source and cause of the earthquakes next week after expanding the monitoring network.
Volcanoes in the Manuʻa Islands are monitored with a limited real-time seismic network consisting of four microseismometers on Tutuila, Taʻū, and Ofu-Olosega Islands. HVO staff are working with the NOAA Pago Pago National Weather Service Office (NWS) to expand the American Samoa monitoring network. Satellite remote sensing is another tool being used, which may detect heat, volcanic gas, and volcanic ash associated with early phases of volcanic activity.