Magnitude 8.0 - SAMOA ISLANDS REGION

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Earthquake Details

• This event has been reviewed by a seismologist.
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Earthquake Summary

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Felt Reports

At least 110 people killed in Samoa, 22 people in American Samoa and seven people on Niuatoputapu, Tonga. Widespread damage to infrastructure at Pago Pago, American Samoa, in many parts of Samoa and on Niuatoputapu, Tonga. Felt (V) at Apia, Samoa and (IV) at Tafuna, American Samoa. Felt in much of American Samoa, Samoa and northern Tonga. Felt as far away as Wallis and Futuna Islands. A tsunami with wave heights (peak-to-trough) was recorded at: 314 cm at Pago Pago, American Samoa; 140 cm at Apia, Samoa; 47 cm at Rarotonga and 8 cm at Penrhyn, Cook Islands; 14 cm at Nuku`alofa, Tonga; 11 cm at Papeete, French Polynesia.

Tectonic Summary

Versión en Español
The broad-scale tectonics of the Tonga region are dominated by the relative convergence of the Pacific and Australia plates, with the Pacific plate subducting westward beneath the Australia plate at the Tonga trench. At the latitude of the earthquake of September 29, 2009, the Pacific plate moves westward with respect to the interior of the Australia plate at a velocity of about 86 mm/year. The earthquake occurred near the northern end of a 3,000 km long segment of the Pacific/Australia plate boundary that trends north-northeast.; farther north of the earthquake’s source region, the plate boundary trends northwest and then west. The eastern edge of the broad Australia plate may be viewed as a collection of small plates or microplates that move with respect to each other and with respect to the Pacific plate and the Australia plate interior.

On the basis of currently available location and fault mechanism information, we infer that the September 29 earthquake occurred as a normal fault rupture on or near the outer rise of the subducting Pacific plate.

The broad-scale Australia/Pacific plate boundary is one of the most active earthquake regions in the world. Earthquakes occur on the thrust-fault boundary between the Australia and Pacific plates, within the Pacific plate on both sides of the trench, and within and on the boundaries of the small plates that compose the eastern edge of the overall Australia plate.

Tsunami Information

• NOAA West Coast & Alaska Tsunami Warning Center

• NOAA Pacific Tsunami Warning Center

  The earthquake locations and magnitudes cited in these NOAA tsunami bulletins are very preliminary and may be superceded by USGS locations and magnitudes computed using more extensive data sets.

• Tsunami Information Links

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Scientific & Technical Information

• USGS Centroid Moment Tensor Solution
• Global CMT Project Moment Tensor Solution
• Historic Moment Tensor Solutions
• Finite Fault Model
• Phase Data
• Seismicity Cross Section
• Theoretical P-Wave Travel Times
• Energy and Broadband Solution

Additional Information, News Reports

• Urgent Local Tsunami Warning Cancellation for Hawaii from the PTWC
• Final Tsunami Advisory for Hawaii from the PTWC
• Expanding Regional Tsunami Warning Cancellation from the PTWC
• Tsunami Information Statement from the WC/ATWC
• Tsunami warning/watch/advisory for US west coast, British Columbia, and Alaska