August 11, 2014
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On July 5, there was a magnitude (M) 5.9 earthquake offshore Iwate prefecture. This event caused maximum seismic intensity 5 Lower in Iwate prefecture and damage with seriously injured persons.
* On July 8, there was a M5.6 earthquake under the middle eastern Iburi region [southern Ishikari region]. This event caused maximum seismic intensity 5 Lower in Hokkaido and damage with injured persons.
* On July 12, there was a M7.0 earthquake offshore Fukushima prefecture. This event caused tsunami observed along the coasts from Iwate to Fukushima prefectures, with a height of 17 cm at Ayukawa, Ishinomaki city, Miyagi prefecture. This event caused damage with injured persons.
* On July 6, there was a M4.6 earthquake at a depth of approximately 50 km under the eastern Hidaka region. The focal mechanism showed a reverse fault type with a compression axis in a WNW-ESE direction. This event occurred on the boundary between the Pacific and the continental plates.
* On July 8, there was a M5.6 earthquake at a depth of approximately 5 km in the middle eastern Iburi region [southern Ishikari region]. The focal mechanism showed a strike-slip fault type with a compression axis in a WNW-ESE direction. This event occurred within the crust. According to the results of GNSS observation, small crustal deformation was observed at M-Tarumaesan-A observatory.
* On July 21, there was a M6.4 earthquake offshore southeast of Etorofu Island. The focal mechanism showed a reverse fault type with a compression axis in a WNW-ESE direction.
* On July 5, there was a M5.9 earthquake at a depth of approximately 50 km, offshore Iwate prefecture. The focal mechanism showed a reverse fault type with a compression axis in an E-W direction. This event occurred on the boundary between the Pacific and the continental plates.
* On July 12, there was a M7.0 earthquake offshore Fukushima prefecture. The focal mechanism showed a normal fault type with a tension axis in an E-W direction. This event caused tsunami observed along the coasts from Iwate to Fukushima prefectures, with a height of 17 cm at Ayukawa, Ishinomaki city, Miyagi prefecture.
* On July 16, there was a M4.6 earthquake at a depth of approximately 15 km in Hamadori, Fukushima prefecture. The focal mechanism showed a strike-slip fault type with a compression axis in an NNW-SSE direction. This event occurred within the crust.
* On July 1, there was a M6.2 deep earthquake at a depth of approximately 540 km, offshore west of Ogasawara Islands. The focal mechanism of this event had a compression axis in a dip direction of the Pacific plate. This event occurred within the Pacific plate.
* On July 3, there was a M4.0 earthquake at a depth of approximately 10 km in the northern Ibaraki prefecture. The focal mechanism showed a normal fault type with a tension axis in an ENE-WSW direction. In addition, on June 10, there was a M4.8 earthquake at a depth of approximately 5 km. The focal mechanism of this event showed a normal fault type with a tension axis in an E-W direction. These events both occurred within the crust.
* On July 20, there was a M4.5 earthquake at a depth of approximately 60 km under the northern Ibaraki prefecture. The focal mechanism had a compression axis in an N-S direction. This event occurred within the Pacific 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.
There was no remarkable activity.
There was no remarkable activity.
* On August 3, there was a M5.6 earthquake offshore northwest of Amami Oshima (about 100 km west of Amami Oshima). The focal mechanism showed a strike-slip fault type with a tension axis in an NNW-SSE direction.
* On August 6, there was a M4.3 earthquake at a depth of approximately 15 km in the southern Kyoto prefecture. The focal mechanism showed a strike-slip fault type with a compression axis in an E-W direction. This event occurred within the crust.
* On August 10, there was a M6.1 earthquake at a depth of approximately 50 km offshore east of Aomori prefecture. The focal mechanism showed a reverse fault type with a compression axis in a WNW-ESE direction (preliminary report). This event occurred on the boundary between the Pacific and the continental plates.
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.
August 11, 2014
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during July 2014.
(reference)
The following events for the period from July 2013 to late June 2014 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities".
| – Offshore Miyagi Prefecture | M6.0 on August 4, 2013 (Depth of approximately 60 km) |
|
| – 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) |
|
| – Northern Ibaraki Prefecture | M5.4 on December 31, 2013 (Depth of approximately 5 km) |
|
| – Iyonada | M6.2 on March 14, 2014 (Depth of approximately 80 km) |
|
| – Along the Northern Coast of Chile | Mw8.1 on April 2, 2014 | |
| – Ocean Area Near the Izu-Oshima | M6.0 on May 5, 2014 (Depth of approximately 160 km) |
– "On July 8, there was a M5.6 earthquake at a depth of approximately
5 km under the middle eastern Iburi region [southern Ishikari Region].
(Excerpted)":
After this event, there have been 7 earthquakes with seismic intensity 1 or over in the vicinity of the epicenter until July 10. This aftershock activity is decreasing now.
– "On July 12, there was a M7.0 earthquake offshore Fukushima
prefecture. (Excerpted)":
After this event, there were 6 earthquakes with seismic intensity 1 or over in the vicinity of the epicenter until July 29. This aftershock activity is decreasing now.
– "On July 16, there was a M4.6 earthquake at a depth of approximately
15 km in Hamadori, Fukushima prefecture. (Excerpted)":
In addition to this event, in July, there were 7 earthquakes of M3.0 or over in the crust extending from Hamadori, Fukushima prefecture to the northern Ibaraki prefecture. Seismic activity became active in the above mentioned area, after the occurrence of the 2011 off the Pacific Cost of Tohoku Earthquake. Although the aftershock activity is gradually decaying as a whole with some up and downs, the activity is still in higher state than the one before the Tohoku Earthquake.
– 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 Earthquake.
In case of the earthquake (Mw 9.1) offshore west of the northern Sumatra Island in 2004, there were Mw8.6 event after four months, Mw8.5 event after about two and a half years, Mw7.5 event after about five and a half years, and Mw8.6 event 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 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 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.
– From July 23 to 29, in the ocean area near Izu-Oshima, there was a seismic activity in which a M3.7 earthquake (maximum seismic activity 3) was the largest. There were 17 earthquakes with seismic intensity 1 or over until July 29. After July 30, seismic activity has almost decayed. According to the GNSS data, very small crustal deformation was observed at "Oshima-1" observatory during this seismic activity. Recently in the ocean near Izu-Oshima, there were similar seismic activities in July 2007 and October 2010.
– "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 July 28 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, July 28, 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.
– From July 26, a seismic activity began and is still continuing as of August 11 offshore northwest of Amami Oshima (about 100 km west of Amami Oshima). The largest so far is a M5.6 earthquake (maximum seismic activity 3) which occurred on August 3. In the area mentioned above, there are similar seismic activities once in several years.
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: