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Information on the 2011 Great East Japan Earthquake

A massive earthquake of magnitude of 9.0 occurred Friday 11 March, off the Pacific coast of the northeastern part of the Japanese main land (Tohoku Region), causing devastating damages. The Japan Meteorological Agency named this earthquake the 2011 Great East Japan Earthquake.

Earthquake Summary

Date and Time: 11 March 2011 14:46 JST (05:46 UTC)
Magnitude: 9.0 (the largest earthquake recorded in Japan)
Hypocenter: 38° 6.2′ N, 142° 51.6′ E (130km ESE off Oshika Peninsula) Depth 24km
Mechanism: Reverse fault type with WNW-ESE compressional axis (by CMT analysis)
Earthquake Early Warning: Issued 8.6 seconds after the detection of the first P-wave at the nearest seismic station
JMA Seismic Intensity:
7 (Max) Kurihara City of Miyagi Prefecture
6+ 28 cities and towns in Miyagi, Fukushima, Ibaraki, and Tochigi Prefectures
6- or weaker Observed nationwide from Hokkaido to Kyushu
Tsunami Warnings and Advisories:
Date and Time Action Number of Areas (Total: 66 areas)
Warning
(3m or higher)		 Warning
(Up to 2m)		 Advisory
(About 0.5m)
11 March 2011 14:49 JST (05:49 UTC) Issued 3 5 15
11 March 2011 15:14 JST (06:14 UTC) Increased 6 7 23
11 March 2011 15:30 JST (06:30 UTC) Increased 10 24 11
11 March 2011 16:08 JST (07:08 UTC) Increased 17 19 17
11 March 2011 18:47 JST (09:47 UTC) Increased 17 19 18
11 March 2011 21:35 JST (12:35 UTC) Increased 17 22 19
11 March 2011 22:53 JST (13:53 UTC) Increased 18 21 19
12 March 2011 03:20 JST (18:20 UTC) Increased 18 21 27
12 March 2011 13:50 JST (04:50 UTC) Decreased 4 11 26
12 March 2011 20:20 JST (11:20 UTC) Decreased 0 4 21
13 March 2011 07:30 JST (22:30 UTC) Decreased 0 0 15
13 March 2011 17:58 JST (08:58 UTC) Lifted 0 0 0
Observed Tsunami: 9.3m or higher at Soma (Fukushima Pref.), 8.6m or higher at Ishinomaki (Miyagi Pref.), etc

Aftershocks (as of 30 April 2012)

Largest Aftershock: Magnitude 7.6 at 11 March 2011 15:15 JST (06:15 UTC)
Number:
6 (magnitude 7 or greater)
102 (magnitude 6 or greater)
671 (magnitude 5 or greater)

More Info on Aftershock / Aftershock Outlook

Status of Observation Facilities

After the earthquake on 11 March, many weather observation data from AMeDAS (JMA's automated weather observation and collection system) stations in Northern Japan had been suspended due to tsunami damage, network failure, and power outage. As of 15 April, JMA has resumed most of its AMeDAS stations. You can see the related story on recovery of weather observation systems.

In addition, NTT docomo (a mobile telecommunication company in Japan) has provided JMA with meteorological observation data at its 5 environmental monitoring stations (verified and notified in advance) near the tsunami affected areas in Tohoku District, based on the Meteorological Service Law.

Seismometers, seismic intensity stations, and tidal gauges are also recovered as follows.

Number of troubled facilities Total number of facilities
11 March 2011 16 May 2012
Seismometers 21 0 (Tohoku District) 26
Seismic Intensity Stations 55 1 (Tohoku District) 87
Tidal Gauges 20 2 (Tohoku District) 25

Charts (PDF)