Disaster replay

2011 Tōhoku earthquake: foreshocks and aftershocks

Two days before the magnitude 9.1 Tōhoku earthquake of 11 March 2011, a magnitude 7.3 earthquake struck in the same area. This replay starts on that day and shows every earthquake of magnitude 5 or more the USGS catalog holds within 600 km over the following month.

The USGS catalog holds 588 earthquakes of magnitude 5.0 or more within 600 km between 9 Mar 2011 and 8 Apr 2011. The largest was magnitude 9.1 on 11 Mar 2011 at 05:46 UTC. The largest after it was magnitude 7.9, 29 minutes later. In the first 24 hours after the largest earthquake the catalog holds 303 more. 26 came before it.

Replay

Press play, or drag the time slider under the map. Each circle is one earthquake, sized by magnitude, and it stays on the map once it has happened. Times are UTC.

The largest earthquakes

Date and time (UTC)MagnitudeDepthUSGS event
11 Mar 2011 05:46 9.1 29 km 2011 Great Tohoku Earthquake, Japan
11 Mar 2011 06:15 7.9 43 km 47 km E of ?arai, Japan
11 Mar 2011 06:25 7.7 19 km 272 km ESE of Kamaishi, Japan
9 Mar 2011 02:45 7.3 32 km 120 km SE of ?funato, Japan
7 Apr 2011 14:32 7.1 42 km 29 km ESE of Ishinomaki, Japan
11 Mar 2011 06:08 6.7 3 km 134 km ESE of Kamaishi, Japan
11 Mar 2011 06:18 6.6 16 km 133 km ENE of Hasaki, Japan
11 Mar 2011 11:36 6.6 26 km 50 km ESE of ?tsuchi, Japan
9 Mar 2011 21:24 6.5 15 km 128 km SE of ?funato, Japan
11 Mar 2011 06:20 6.5 49 km 115 km ENE of Hasaki, Japan

Earthquakes each day

588 of magnitude 5 or more, 63 of 6 or more, 5 of 7 or more.

Day (UTC)Earthquakes
9 Mar 2011 22
10 Mar 2011 4
11 Mar 2011 277
12 Mar 2011 77
13 Mar 2011 38
14 Mar 2011 28
15 Mar 2011 18
16 Mar 2011 12
17 Mar 2011 15
18 Mar 2011 13
19 Mar 2011 3
20 Mar 2011 12
21 Mar 2011 3
22 Mar 2011 21
23 Mar 2011 5
24 Mar 2011 5
25 Mar 2011 3
26 Mar 2011 2
27 Mar 2011 4
28 Mar 2011 2
29 Mar 2011 2
30 Mar 2011 4
31 Mar 2011 2
1 Apr 2011 5
2 Apr 2011 1
3 Apr 2011 3
4 Apr 2011 3
5 Apr 2011 1
6 Apr 2011 1
7 Apr 2011 2
8 Apr 2011 0

What these numbers can and cannot show

These are the earthquakes the USGS catalog holds at or above magnitude 5.0 within 600 km of 38.30, 142.40. Smaller earthquakes are not included. In the first hours after a very large earthquake many aftershocks are not recorded, because their signals overlap in the seismograms, so the first day's count is lower than what happened. The circle is a fixed distance, so an unrelated earthquake inside it is counted and a distant aftershock outside it is not.

Snapshot of the USGS Comprehensive Earthquake Catalog downloaded 13 Sep 2026; USGS continues to revise past magnitudes and locations. The exact USGS query. Timeline player: Leaflet.TimeDimension (MIT licence).

Questions

How many earthquakes does the 2011 Tōhoku earthquake: foreshocks and aftershocks replay show?

The USGS catalog holds 588 earthquakes of magnitude 5.0 or more within 600 km between 9 Mar 2011 and 8 Apr 2011. The largest was magnitude 9.1 on 11 Mar 2011 at 05:46 UTC. The largest after it was magnitude 7.9, 29 minutes later. In the first 24 hours after the largest earthquake the catalog holds 303 more. 26 came before it.

What was the largest earthquake after the main shock?

Magnitude 7.9 on 11 Mar 2011 06:15 UTC, 29 minutes after the largest earthquake, according to the USGS catalog.

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