April 9, 2014
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On March 14, there was a magnitude (M) 6.2 earthquake under Iyonada. This event caused maximum seismic intensity 5 Upper in Ehime prefecture and damage with injured persons.
There was no remarkable activity.
* On March 17, there was a M5.1 earthquake at a depth of approximately 35 km, offshore Fukushima prefecture. The focal mechanism showed a strike-slip fault with a tension axis in a WNW-ESE direction. This event occurred within the continental plate.
* 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.
* On March 14, there was a M6.2 earthquake at a depth of approximately 80 km under Iyonada. The focal mechanism had a tension axis in an ENE-WSW direction. This event occurred within the subducting Philippine Sea plate.
* On March 3, there was a M6.4 earthquake at a depth of approximately 120 km, offshore north-west of Okinawa Main Island. The focal mechanism had a compression axis in a direction of the subducting Philippine Sea plate. This event occurred within the Philippine Sea plate.
* On March 3, there was a M5.0 earthquake at a depth of approximately 45 km under the ocean near Okinawa Main Island. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction.
* On March 26, there was a M5.3 earthquake offshore east of Satsunan Islands. The focal mechanism showed a normal fault with a tension axis in an ENE-WSW direction. This event occurred within the Philippine Sea plate, east of the Nansei Islands Arc.
* On March 19, there was a M6.0 earthquake at a depth of approximately 20 km near Taiwan. The focal mechanism had a compression axis in an N-S direction.
* On April 2, at 08:46 (JST), there was a moment magnitude (Mw) 8.1 earthquake along the northern coast of Chile. This event caused tsunami which was observed along the Pacific coast from Hokkaido to Kyushu, and at Izu-Ogasawara Islands, especially 0.6m (preliminary) height at Kuji Port (Iwate 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 Nazca and the South American plates.
In the vicinity of this event, a M6.7 earthquake occurred on March 17 and the seismic activity has continued afterwards.
Note: [ ] was the regional name of the epicenter used in the Japan
Meteorological Agency announcement.
GNSS (Global Navigation Satellite System) is a general name of satellite positioning system such as GPS.
April 9, 2014
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during March 2014.
(reference)
The following events for the period from March 2013 to late February 2014 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities".
| – Near Awajishima | M6.3 on April 13, 2013 (Depth of approximately 15 km) |
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| – Under the Ocean Near Miyakejima | M6.2 on April 17, 2013 (Depth of approximately 10 km) |
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| – Offshore Miyagi Prefecture | M5.9 on April 17, 2013 (Depth of approximately 60 km) |
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| – Offshore Fukushima Prefecture | M6.0 on May 18, 2013 (Depth of approximately 45 km) |
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| – Offshore Miyagi Prefecture | M6.0 on August 4, 2013 (Depth of approximately 60 km) |
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| – Hamadori, Fukushima Prefecture | M5.9 on September 20, 2013 (Depth of approximately 15 km) |
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| – Offshore Fukushima Prefecture | M7.1 on October 26, 2013 | |
| – Southern Ibaraki Prefecture | M5.5 on November 10, 2013 (Depth of approximately 65 km) |
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| – Northern Ibaraki Prefecture | M5.4 on December 31, 2013 (Depth of approximately 5 km) |
There is no supplementary information for the Hokkaido region.
There is no supplementary information for the Tohoku region.
– Within the aftershock area, the number of earthquakes of M4.0 or over, during one year from March 2012 (from March 2012 to February 2013) became under one fifth smaller, and during one year from March 2013 (from March 2013 to February 2014) became under one tenth smaller, than the number during about one year just after the Tohoku-Oki Earthquake.
In case of the earthquake (Mw 9.1) offshore west of the northern Sumatra Island in 2004, there were Mw8.6 after four months, Mw8.5 after about two and a half years, Mw7.5 after about five and a half years, and Mw8.6 after about seven and a half years in the region of outer rise. Thus, there have been large earthquakes for long period within the source area and its surroundings.
According to the GNSS data, crustal deformation which is thought to be postseismic deformation has still been observed in a wide area from the Tohoku through the Kanto-Chubu regions. During about one month just after the Tohoku-Oki Earthquake, at the maximum value, the horizontal movement was 30 cm, and the vertical subsidence and upheaval were 6 cm and 5 cm respectively. The deformation is decaying: the horizontal deformation was up to around 1cm, and the vertical deformation was 1cm or so during the recent one month.
Although the aftershock activity is gradually decaying as a whole, the activity is still in higher state than the one before the Tohoku-Oki Earthquake. In addition there are overseas examples for gigantic earthquakes. Synthetically judging from these facts, within the aftershock area and its surroundings, there is a fear that large earthquakes will occur from now on, and there is a possibility that it will be hit by strong shaking and high tsunami. It is necessary to do care continuously for it.
–"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 24 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 24, 2014)
"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 Kinki-Chugoku-Shikoku region.
There is no supplementary information for Kyushu-Okinawa region.
– "On April 2, at 08:46 (JST), there was a moment magnitude
(Mw) 8.1 earthquake along the northern coast of Chile. (Excerpted) ":
In the vicinity of the event, a M8.5 earthquake in 1868 and a M8.3 one in 1877 occurred and tsunamis associated with these are observed along the Pacific coast of Japan.
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: