April 10, 2012
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On March 1, there was a M5.3 earthquake offshore Ibaraki prefecture. This event had a maximum seismic intensity 5 Lower in Ibaraki prefecture.
* On March 10, there was a M5.4 earthquake in northern Ibaraki prefecture. This event had a maximum seismic intensity 5 Lower in Ibaraki prefecture.
* On March 14, there was a M6.9 earthquake offshore Sanriku. This event caused tsunamis on the Pacific coast from the Hokkaido to northern Tohoku regions with tsunami heights of 21 cm at Harbor Hachinohe (Aomori prefecture).
* On March 14, there was a M6.1 earthquake offshore east of Chiba prefecture. This event had a maximum seismic intensity 5 Upper in Ibaraki and Chiba prefectures and caused damage with casualties.
* On March 27, there was a M6.6 earthquake offshore Iwate prefecture. This event had a maximum seismic intensity 5 Lower in Iwate and Miyagi prefectures.
There was no remarkable activity.
* On March 14 at 18:08 (JST), there was a M6.9 earthquake offshore Sanriku. The focal mechanism showed a normal fault with a tension axis in an N-S direction. This event occurred within the Pacific plate. There were brisk aftershock activities such as a M6.0 earthquake at 19:49 on the same day. This event caused tsunamis on the Pacific coast from the Hokkaido to northern Tohoku regions with tsunami heights of 21 cm at Harbor Hachinohe (Aomori prefecture).
* On March 19, there was a M5.0 earthquake at a depth of approximately 65 km, offshore east of Aomori prefecture. The focal mechanism showed a reverse fault with a compression axis in an E-W direction. This event occurred on the boundary between the Pacific and the continental plates.
* On March 27, there was a M6.6 earthquake at a depth of approximately 20 km, offshore Iwate prefecture. The focal mechanism showed a reverse fault with a compression axis in an NE-SW direction. This event occurred within the crust of the continental plate.
* On March 1, there was a M5.3 earthquake at a depth of approximately 55 km, offshore Ibaraki prefecture. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction. This event occurred on the boundary between the Pacific and the continental plates.
* On March 10, there was a M5.4 earthquake at a depth of approximately 5 km in northern Ibaraki prefecture. The focal mechanism showed a normal fault with a tension axis in an NE-SW direction. This event occurred within the crust.
* On March 14, there was a M6.1 earthquake at a depth of approximately 15 km, offshore east of Chiba prefecture. The focal mechanism showed a normal fault with a tension axis in an E-W direction. This event occurred within the crust. In addition to this event, there was a sequence of seismicity such as a M4.6 earthquake on March 27. According to the GNSS data, crustal movements associated with this event were observed and there was a movement of approximately 1 cm toward the east at the Choshi station (Chiba prefecture).
* On March 16, there was a M5.3 earthquake at a depth of approximately 95 km under southern Saitama prefecture. This event occurred near the boundary between the Pacific and the Philippine Sea plates. The focal mechanism showed a reverse fault with a compression axis in an ENE-WSW direction.
* In the GNSS data for the Tokai region, there have been no changes of activity which are likely to be associated with the Tokai earthquake.
There was no remarkable activity.
* On March 12, there was a M3.9 earthquake at a depth of approximately 10 km in the Kumamoto region, Kumamoto prefecture. The focal mechanism showed a normal fault with a tension axis in an N-S direction. This event occurred within the crust.
* On April 1, there was a M5.9 earthquake at a depth of approximately 55 km, offshore Fukushima prefecture. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction. This event occurred on the boundary between the Pacific and the continental plates.
Note: GNSS (Global Navigation Satellite System) is a general name of satellite positioning system such as GPS.
April 10, 2012
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during March 2012.
(reference)
The following events for the period from March 2011 to the end of February 2012 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activitie"
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– Offshore Sanriku |
M7.3 on March 9, 2011 |
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– The 2011 off the Pacific Coast of Tohoku Earthquake | M9.0 on March 11, 2011 (Depth of approximately 25 km) |
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– Izu Region, Shizuoka Prefecture | M4.6 on March 11, 2011 (Depth of approximately 5 km) |
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– Near the Border between Nagano and Niigata Prefectures | M6.7 on March 12, 2011 (Depth of approximately 10 km) |
| – Eastern Shizuoka Prefecture | M6.4 on March 15, 2011 (Depth of approximately 15 km) |
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| – Northern Ibaraki Prefecture | M6.1 on March 19, 2011 (Depth of approximately 5 km) |
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– Hamadori, Fukushima Prefecture | M6.0 on March 23, 2011 (Depth of approximately 10 km) |
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– Southern Ibaraki Prefecture | M4.8 on March 24, 2011 (Depth of approximately 50 km) |
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– Northern Inland, Akita Prefecture | M5.0 on April 1, 2011 (Depth of approximately 10 km) |
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– Southern Ibaraki Prefecture | M5.0 on April 2, 2011 (Depth of approximately 55 km) |
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– Offshore Miyagi Prefecture | M7.1 on April 7, 2011 (Depth of approximately 65 km) |
| – Hamadori, Fukushima Prefecture | M7.0 on April 11, 2011 (Depth of approximately 5 km) |
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| – Northern Nagano Prefecture | M5.6 on April 12, 2011 (Very shallow depth) |
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| – Offshore East of Chiba Prefecture | M6.4 on April 12, 2011 (Depth of approximately 25 km) |
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| – Southern Ibaraki Prefecture | M5.9 on April 16, 2011 (Depth of approximately 80 km) |
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| – Near the Border between Nagano and Niigata Prefectures | M4.9 on April 17, 2011 (Depth of approximately 10 km) |
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| – Southern Inland, Akita Prefecture | M4.9 on April 19, 2011 (Depth of approximately 5 km) |
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| – Offshore East of Chiba Prefecture | M6.0 on April 21, 2011 (Depth of approximately 45 km) |
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– Hamadori, Fukushima Prefecture | M5.2 on May 6, 2011 (Depth of approximately 5 km) |
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– Chuetsu Region, Niigata Prefecture | M4.7 on June 2, 2011 (Depth of approximately 5 km) |
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– Offshore Iwate Prefecture | M6.9 on June 23, 2011 (Depth of approximately 35 km) |
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– Central Nagano Prefecture | M5.4 on June 30, 2011 (Depth of approximately 5 km) |
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– Northern Wakayama Prefecture | M5.5 on July 5, 2011 (Depth of approximately 5 km) |
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– Offshore Sanriku | M7.3 on July 10, 2011 |
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– Southern Ibaraki Prefecture | M5.4 on July 15, 2011 (Depth of approximately 65 km) |
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– Suruga Bay | M6.2 on August 1, 2011 (Depth of approximately 25 km) |
| – Offshore Fukushima Prefecture | M6.5 on August 19, 2011 (Depth of approximately 50 km) |
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– Central Hidaka Region | M5.1 on September 7, 2011 (Depth of approximately 10 km) |
| – Northern Ibaraki Prefecture | M5.2 on September 21, 2011 (Depth of approximately 10 km) |
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| – Hamadori, Fukushima Prefecture | M5.4 on September 29, 2011 (Depth of approximately 10 km) |
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| – Kumamoto Region, Kumamoto Prefecture | M4.5 on October 5, 2011 (Depth of approximately 10 km) |
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– Northern Ibaraki Prefecture | M5.3 on November 20, 2011 (Depth of approximately 10 km) |
| – Northern Hiroshima Prefecture | M5.4 on November 21, 2011 (Depth of approximately 10 km |
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| – Offshore Urakawa | M6.2 on November 24, 2011 (Depth of approximately 45 km) |
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– Offshore Fukushima Prefecture | M5.1 on January 23, 2012 (Depth of approximately 50 km) |
| – Eastern Yamanashi Prefecture-Fujigoko | M5.4 on January 28, 2012 (Depth of approximately 20 km) | |
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– Near Sado | M5.7 on February 8, 2012 (Depth of approximately 15 km) |
| – Northern Ibaraki Prefecture | M5.2 on February 19, 2012 (Depth of approximately 5 km) |
There is no supplementary information for the Hokkaido region.
– Since mid-March, 2011, a series of seismicity has been continuing in the vicinity of the prefectural border of Aizu, Fukushima prefecture and the Okitama region, Yamagata prefecture, but it has been decaying.
"On March 10, there was a M5.4 earthquake at a depth of approximately
5 km in northern Ibaraki prefecture. (Excerpted)":
In the region from Hamadori, Fukushima prefecture through northern Ibaraki
prefecture, brisk seismicity has been continuing since the 2011 off the
Pacific Coast of Tohoku Earthquake.
– In the aftershock area of the 2011 off the Pacific Coast of Tohoku Earthquake, brisk seismicity has been seen. There is fear that large aftershocks will occur from now on, and there is a possibility that it will be hit by strong shaking and high tsunami. Crustal movements to the east which are thought to be the postseismic deformation have still been observed in a wide area from the Tohoku through the Kanto-Chubu regions, but they have gradually been decaying.
"In the GNSS data for the Tokai region, there have been no changes
of activity which are likely to be associated with the Tokai earthquake":
(This evaluation is in agreement with the views presented at the regular
meeting on March 26 of the Assessment Committee for Areas under Intensified
Measures against Earthquake Disaster (reference below).)
(Reference)
Recent seismic and crustal activity in the Tokai region and its vicinity (Seismological and Volcanological Department, Japan Meteorological Agency, March 26, 2012)
"No changes of activity which are likely to be associated with the Tokai earthquake have been observed until now. (Excerpted)"
There is no supplementary information for the Kinki-Chugoku-Shikoku region.
There is no supplementary information for the Kyushu-Okinawa region.
Reference 1
Earthquakes that are described in the "Evaluation of Seismic Activity" (Monthly Report of Seismic Activity in Japan) have the following features.
Reference 2
Information that is described in the "Supplementary Information to the Evaluation" includes: