Update March 13, 2011: Japan’s Meteorological Agency says the magnitude of Friday’s earthquake that hit the Pacific coast of northeastern Japan was 9.0 instead of 8.8 as earlier announced. The agency made the correction on Sunday morning after analyzing seismic waves and other data. The magnitude is equivalent to that of the 2004 earthquake off Sumatra, Indonesia, which triggered massive tsunamis in the Indian Ocean. The agency says the focal zone of Friday’s quake was about 500 kilometers long and 200 kilometers wide. Destructive movement along the fault continued for more than 5 minutes. The Meteorological Agency says only 4 other quakes in the world have recorded magnitudes of 9 or over. The largest was the magnitude 9.5 quake that hit the Chilean coast in 1960, killing more than 1,600. The quake also triggered tsunamis in Japan, leaving 142 people dead. The 2004 quake off Sumatra registered a magnitude of 9.1. Subsequent giant tsunamis killed more than 200,000 people.

Update March 12, 2011: For detailed technical information, the US Geological Survey pages for this ‘quake are here. The Boston Globe has a good album of photos in their Big Picture blog series.

March 10, 2011: An 8.9 magnitude earthquake has struck Japan today. The epicenter, located just off Japan’s Pacific coast near Sendhai, has triggered a 4 meter high tsunami which is devastating a large area of the adjacent coastline. Tsunami warnings are currently up for the entire North American west coast. A 4.5 magnitude earthquake has just been reported in Hawaii, although officials there don’t know if its associated with the Sendhai quake. Check in from time to time with the NOAA Pacific Tsunami Centre and the Pacific Disaster Center for recent alerts. NHK, the national broadcaster in Japan, is providing updates and contact information in English on NHK World. Please use the link sparingly so that people with a bona-fide need can access the link.

Magnitude 8.9 Earthquake - Japan

WEHW40 PHEB 111133
TSUHWX
HIZ001>003-005>009-012>014-016>021-023>026-111333-
/O.CON.PHEB.TS.W.0001.000000T0000Z-000000T0000Z/
BULLETIN
TSUNAMI MESSAGE NUMBER 7
NWS PACIFIC TSUNAMI WARNING CENTER EWA BEACH HI
133 AM HST FRI MAR 11 2011
TO – CIVIL DEFENSE IN THE STATE OF HAWAII
SUBJECT – TSUNAMI WARNING SUPPLEMENT
A TSUNAMI WARNING CONTINUES IN EFFECT FOR THE STATE OF HAWAII.
AN EARTHQUAKE HAS OCCURRED WITH THESE PRELIMINARY PARAMETERS
ORIGIN TIME – 0746 PM HST 10 MAR 2011
COORDINATES – 38.3 NORTH 142.4 EAST
LOCATION – NEAR EAST COAST OF HONSHU JAPAN
MAGNITUDE – 8.9 MOMENT
MEASUREMENTS OR REPORTS OF TSUNAMI WAVE ACTIVITY
GAUGE LOCATION LAT LON TIME AMPL PER
TOSASHIMIZU SHIKOKU 32.8N 133.0E 0946Z 0.84M / 2.8FT 28MIN
ADAK AK 51.9N 176.6W 1034Z 0.35M / 1.2FT 22MIN
YAP FM 9.5N 138.1E 1013Z 0.15M / 0.5FT 88MIN
LEGASPI PH 13.1N 123.8E 1022Z 0.29M / 1.0FT **MIN
MIDWAY 28.2N 177.4W 1028Z 1.56M / 5.1FT 80MIN
DART 21415 50.2N 171.8E 0845Z 0.27M / 0.9FT 52MIN
WAKE US 19.3N 166.6E 0928Z 0.39M / 1.3FT 14MIN
NAHA OKINAWA JP 26.2N 127.7E 0901Z 0.25M / 0.8FT 60MIN
SAIPAN US 15.2N 145.7E 0916Z 0.65M / 2.1FT 30MIN
OMAEZAKI HONSHU JP 34.6N 138.2E 0818Z 1.42M / 4.6FT 56MIN
DART 21419 44.5N 155.7E 0716Z 0.40M / 1.3FT 20MIN
DART 21413 30.5N 152.1E 0659Z 0.76M / 2.5FT 32MIN
HANASAKI HOKKAIDO J 43.3N 145.6E 0657Z 2.79M / 9.2FT 76MIN
DART 21401 42.6N 152.6E 0643Z 0.67M / 2.2FT 40MIN
DART 21418 38.7N 148.7E 0619Z 1.08M / 3.5FT 06MIN
LAT – LATITUDE (N-NORTH, S-SOUTH)
LON – LONGITUDE (E-EAST, W-WEST)
TIME – TIME OF THE MEASUREMENT (Z IS UTC IS GREENWICH TIME)
AMPL – TSUNAMI AMPLITUDE MEASURED RELATIVE TO NORMAL SEA LEVEL.
IT IS …NOT… CREST-TO-TROUGH WAVE HEIGHT.
VALUES ARE GIVEN IN BOTH METERS(M) AND FEET(FT).
PER – PERIOD OF TIME IN MINUTES(MIN) FROM ONE WAVE TO THE NEXT.
NOTE – DART MEASUREMENTS ARE FROM THE DEEP OCEAN AND THEY
ARE GENERALLY MUCH SMALLER THAN WOULD BE COASTAL
MEASUREMENTS AT SIMILAR LOCATIONS.
EVALUATION
A TSUNAMI HAS BEEN GENERATED THAT COULD CAUSE DAMAGE ALONG COASTLINES OF ALL ISLANDS IN THE STATE OF HAWAII. URGENT ACTION SHOULD BE TAKEN TO PROTECT LIVES AND PROPERTY.
A TSUNAMI IS A SERIES OF LONG OCEAN WAVES. EACH INDIVIDUAL WAVE CREST CAN LAST 5 TO 15 MINUTES OR MORE AND EXTENSIVELY FLOOD COASTAL AREAS. THE DANGER CAN CONTINUE FOR MANY HOURS AFTER THE INITIAL WAVE AS SUBSEQUENT WAVES ARRIVE. TSUNAMI WAVE HEIGHTS
CANNOT BE PREDICTED AND THE FIRST WAVE MAY NOT BE THE LARGEST. TSUNAMI WAVES EFFICIENTLY WRAP AROUND ISLANDS. ALL SHORES ARE AT RISK NO MATTER WHICH DIRECTION THEY FACE. THE TROUGH OF A TSUNAMI WAVE MAY TEMPORARILY EXPOSE THE SEAFLOOR BUT THE AREA WILL
QUICKLY FLOOD AGAIN. EXTREMELY STRONG AND UNUSUAL NEARSHORE CURRENTS CAN ACCOMPANY A TSUNAMI. DEBRIS PICKED UP AND CARRIED BY A TSUNAMI AMPLIFIES ITS DESTRUCTIVE POWER. SIMULTANEOUS HIGH TIDES OR HIGH SURF CAN SIGNIFICANTLY INCREASE THE TSUNAMI HAZARD.
THE ESTIMATED ARRIVAL TIME IN HAWAII OF THE FIRST TSUNAMI WAVE IS 0307 AM HST FRI 11 MAR 2011 MESSAGES WILL BE ISSUED HOURLY OR SOONER AS CONDITIONS WARRANT.

EWR monitors Mt Redoubt in Alaska as a result of the eruption of Redoubt in April 2009. This is the seismic trace of the Japan Earthquake and related Pacific rim activity, as recorded on Redoubt webicorder:

Webicorder RSO at Mt Redoubt in Alaska recording the Japan earthquake

The image below is the current RSO seismic webicorder trace for Mt. Redoubt in Alaska. Tremor activity continues in the Rim of Fire, since the Sendhai earthquake went off on the 10th. This image updates in realtime, to give you an idea of the aftershock scenario from a major quake. The challenge for volcanologists is to separate seismic activity of their target (Mt. Redoubt, in this case) from the background activity from unrelated areas.

Webicorder update is presently offline from AVO
Webicorder RSO_EHZ_AV 24hr. (refresh for webicorder update – Active trace is the very bottom one).