Background and Scope - Tohoku, Japan Earthquake and Tsunami of 2011 - page 11

most of the Pacific Basin fell under tsunami warnings or watches for the estimated
8.8 to 8.9 magnitude earthquake.
The West Coast Alaska Tsunami Warning Center (WCATWC) issued a Tsunami
Warning status for Alaska, Oregon, and California at 10:05 UTC (4 hours, 19 minutes
after the start of the earthquake). Adjusted advisories followed as waves reached
areas around the Pacific Basin. Hilo, Hawaii, reported a preliminary wave height of
1.41 m at 14:09 UTC (8 hours, 23 minutes after the earthquake); Crescent City,
California, reported a 2.02 m wave height, at 16:57 UTC (11 hours and 11 minutes
after the earthquake) (PTWC 2011). The times of these reports did not correspond to
the first arrival time of the waves or to verified de-tided tsunami heights. Rather,
these reports served to update the emergency response activities of the warning
centers. Section 1.5 provides a discussion of the tsunami heights and wave
propagation from the Great East Japan event. On March 12 at 6:36 UTC (24 hours, 5
minutes after the earthquake), shortly after Arica, Chile reported a wave height of
1.25 m, the PTWC cancelled all tsunami watches and warnings. WCATWC cancelled
its advisories on March 12 at 16:10 UTC (34 hours, 24 minutes after the earthquake).
JMA cancelled all tsunami advisories on March 13 at 8:58 UTC (51 hours and 12
minutes after the earthquake) and revised the earthquake's magnitude to its final
value of 9.0.
On March 11 at 10:03 UTC (4 hours, 17 minutes after the earthquake), the office of
the prime minister of Japan issued a status of nuclear emergency due to the possibility
of nuclear meltdown and radiation releases at three nuclear power facilities in the
tsunami-affected area. The facilities included the plant at Onagawa and plants one
(Dai-Ichi) and two (Dai-Ni) at Fukushima. After 6 hours, authorities deemed the plant
at Onagawa safe but expanded the evacuation zone around the Fukushima plants as
they tried to balance the need to provide cooling water to the reactors with possible
radiation releases from escaping water and steam. On March 12, at 9:25 UTC (27
hours, 39 minutes after the earthquake), the evacuation zone was extended to 20 km
around Fukushima Dai-Ichi and 10 km around Dai-Ni. The same day, Japan's
Nuclear and Industrial Safety Agency (JNISA) issued a statement at 20:10 UTC
classifying Reactor Unit 1 at Fukushima Dai-Ichi as a level 4 “Accident with Local
Consequences” event on the International Nuclear and Radiological Event Scale
(INES). Prompted by the number of failures and the complex nature of the disaster,
JNISA eventually revised the accident level for both Fukushima plants to level 7.
1.3.4AffectedAreas,Casualties,andResponse
As of 15 July, the estimated number of deaths from the Great East Japan earthquake
and tsunami had reached 15,562, with 5,306 missing and 5,690 injured in the event.
Over 99% of the fatalities occurred in Miyagi, Iwate, and Fukushima prefectures
(Table 3). These three prefectures also reported the highest numbers of missing
persons. Within the entire inundated areas of the prefectures alone, the average
percentage of people either dead or missing varied between 2.6 and 6.3%.
Communities within the Otsuchi and Rikuzen-Takata in the Iwate Prefecture and
Onagawa in the Miyagi Prefecture recorded the highest loss percentages (14.5%, 13%,