Magnitude 8.3 Quake Strikes Samoa Islands Region
Posted by feww on September 29, 2009
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Massive Earthquake Measuring up to 8.4 Mw Strikes Samoa Islands Region
The mainshock occurred on Tuesday, September 29, 2009 at 17:48 UTC [Tuesday, September 29, 2009 at 06:48 AM at epicenter,] which struck at striking at a depth of about 10km. The mainshock has since been followed by at least two dozen aftershocks both locally and in the neighboring Tonga region, the largest of which measures 6.2 Mw so far.
The large earthquake generated 1.6-meter waves in American Samoa, Apia and Pago Pago. The Pacific Tsunami Warning Center (NOAA/NWS/PTWC) issued a tsunami warning which has since been canceled.
According to local news, at least 4 villages were wiped off, leaving more than 40 dead and up to a 100 injured. Most of the casualties are believe to be children. More casualties are expected as local reports are received.
How large was this earthquake?
The GFZ Potsdam – Earthquake Bulletin reported the mainshock as M 8.2, while the European-Mediterranean Seismological Center recorded it as 8.1Mw. However, FEWW believes the quake measured up to 8.4Mw.
On June 26, 1917, a magnitude 8.4 earthquake struck the neighboring Tonga region at a depth of about 25km, some 115 km northwest of today’s event.
Tsunami Location Map
Click on image to enlarge. Source NOAA
This advisory is in effect for California, and Oregon
- A tsunami advisory indicates a tsunami which may produce strong currents and is dangerous to those in or very near the water is expected.
- Large inundations are not expected in areas under advisory status.
- Advisories will be cancelled, extended, or upgraded to a warning depending on the event severity.
- Advisories are issued when the expected tsunami amplitude is in the range of 0.3 to 1 meter.
Tsunami Propagation Map
Click on image to enlarge. Source: NOAA/WCATWC
US Tsunami waves initial arrival times
Tsunami waves initial arrival times including wave amplitude above sea level (ASL) at the US coastal areas.
Tsunami Travel Time Map
Map of Tsunami Advisory – Japan
Map of Tsunami Advisory for Japan. Yellow highlights indicate tsunami heights of about 0.5m (50cm). Original Map: Japan Meteorological Agency (JMA). Image may be subject to copyright. Click on image to enlarge.
GFZ Potsdam – Earthquake Bulletin
Region: Samoa Islands Region
Time: 2009-09-29 17:48:10.3 UTC
Epicenter: 172.04°W 15.49°S
Depth: 10 km
Status: manually revised
USGS downgraded the mainshock to 8.0Mw.
10-degree Map Centered at 15°S,170°W
Earthquake Location Map. Original Map: USGS. Enhanced by FEWW.
Historic Seismicity (Mag 7 or greater EQs since 1900)
Major Tectonic Boundaries: Subduction Zones -purple, Ridges -red and Transform Faults -green
Original Image: USGS. Enhanced by FEWW.
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