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USGS Volcano Notice - DOI-USGS-HVO-2022-08-24T19:55:44-07:00

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HAWAIIAN VOLCANO OBSERVATORY DAILY UPDATE
U.S. Geological Survey
Wednesday, August 24, 2022, 5:01 PM HST (Thursday, August 25, 2022, 03:01 UTC)


TA'U ISLAND (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

There has been no significant change to the earthquake activity beneath or around Taʻū and Ofu-Olosega Islands since yesterday’s update. USGS staff have installed two advanced seismometers on Taʻū island and another is being installed on Ofu island today. USGS earthquake experts are currently reviewing and evaluating the data quality as it becomes available. 

Over the past several days approximately 20 earthquakes per hour have been recorded. Though the exact count isn't available, the number of recorded earthquakes in the past 24 hours appears slightly lower. Preliminary estimates place the source of the earthquakes closer to Taʻū Island than Ofu-Olosega. Estimated magnitudes of most of the largest earthquakes are between magnitude 2 and 3.

At 8:33 p.m. Samoa Standard Time yesterday evening, August 23, residents of the Manuʻa islands and Tutuila island reported a widely-felt earthquake. Light to moderate shaking, with a maximum Intensity of V on the Modified Mercalli Intensity Scale, was reported during the earthquake (https://www.usgs.gov/programs/earthquake-hazards/modified-mercalli-intensity-scale). This earthquake is one of the largest recorded to date since instruments were installed in the Manuʻa islands beginning the second week of August. The magnitude, which is likely magnitude 3 or larger, will be determined at a later date if possible when the American Samoa seismic network has been calibrated. Reports of booming sounds continue to be investigated but to date have not correlated with specific seismic events.   

USGS scientists are monitoring the earthquakes with microseismometers (small and basic earthquake detectors) placed on Tutuila, Taʻū, and Ofu-Olosega Islands. Larger, more sophisticated, and accurate seismometers are being installed this week to form a basic network. Data from the new network will help to accurately locate the earthquakes and develop better assessments of possible future hazards.

Samoan and English language alert level and color code definitions: (PDF download, 57.68 kb) https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/media/files/VOLCANO%20AVIATION%20CODES%20AND%20ALERT%20LEVELS.pdf



OFU-OLOSEGA (VNUM #244010)
14°10'30" S 169°37'5" W, Summit Elevation 2096 ft (639 m)
Current Volcano Alert Level: ADVISORY
Current Aviation Color Code: YELLOW

The earthquake swarm in the Manuʻa Islands (Taʻū and Ofu-Olosega) of American Samoa is continuing without significant change.  See Taʻū volcano summary for details.



Hazards

It is unclear if this unrest will escalate to a volcanic eruption. An eruption could pose significant hazards to residents of American Samoa; these hazards include volcanic gases, 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. 

Currently, the primary hazard of concern is earthquake shaking, although no 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/

    Volcano Monitoring

    Volcanoes in the Manuʻa Islands are monitored with a limited real-time seismic network consisting of six 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 this week. Satellite remote sensing is another tool being used, which may detect heat, volcanic gas, and volcanic ash associated with early phases of volcanic activity.

    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 are unknown.

    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.

    NOAA Weather and Tsunami resources



    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.



    CONTACT INFORMATION:

    HVO, askHVO@usgs.gov—best contact for regular reporting and questions. 
    Ken Hon, HVO Scientist in Charge, USGS khon@usgs.gov
    Natalia Deligne, American Samoa Lead Responding Scientist, USGS ndeligne@usgs.gov 



    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