July 9, 2014
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On June 24, there was a moment magnitude (Mw) 7.9 earthquake under the Rat Islands, Aleutian Islands. Small sea level variations considered as tsunami by this event were observed along the Pacific coasts of Hokkaido and Aomori prefectures.
* On June 26, there was a magnitude (M) 4.8 earthquake at a depth of approximately 50 km, offshore southeast of Nemuro peninsula. The focal mechanism showed a reverse fault type with a compression axis in an NW-SE direction. This event occurred on the boundary between the Pacific and the continental plates.
* On June 8, there was a M5.0 earthquake at a depth of approximately 65 km under southern coast of Iwate prefecture. The focal mechanism had a compression axis in a direction of the subducting Pacific plate. This event occurred within the Pacific plate.
* On June 9, there was a M4.6 earthquake at a depth of approximately 80 km, offshore Miyagi prefecture. The focal mechanism had a compression axis in a direction of the subducting Pacific plate. This event occurred within the Pacific plate.
* On June 15, there was a M5.5 earthquake at a depth of approximately 95 km under the southern inland region, Iwate prefecture. The focal mechanism had a compression axis in a direction of the subducting Pacific plate. This event occurred within the Pacific plate.
* On June 16, there was a M5.8 earthquake at a depth of approximately 50 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.
* On June 16, there was a M5.7 earthquake offshore of Ibaraki prefecture. The focal mechanism of this event showed a normal fault type with a tension axis in an E-W direction.
* On June 17, there was a M5.3 earthquake at a depth of approximately 120 km, offshore south of Boso peninsula. The focal mechanism of this event had a compression axis in a direction of the subducting Pacific plate. This event occurred within the Pacific plate.
* On June 29, there was a M6.4 earthquake under the ocean area near Iwotou Island. The focal mechanism showed a reverse fault type with a compression axis in an NW-SE 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.
There was no remarkable activity.
* On June 24, there was a Mw 7.9 earthquake under the Rat Islands, Aleutian Islands. The focal mechanism had a compression axis in an NNE-SSW direction. This event occurred within the Pacific plate. Small sea level variations considered as tsunami by this event were observed along the Pacific coasts of Hokkaido and Aomori prefecture.
* On July 1, there was a M6.2 earthquake at a depth of approximately 540 km, offshore west of the Ogasawara Islands. The focal mechanism 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 under northern Ibaraki prefecture. The focal mechanism showed a normal fault with a tension axis in an ENE-WSW direction. This event occurred within the crust.
* 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 8, there was a M5.6 earthquake at a depth of approximately 5 km under middle-east Iburi region [southern Ishikari region]. The focal mechanism had a compression axis in a WNW-ESE direction (preliminary report). This event occurred within the crust.
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.
July 9, 2014
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during June 2014.
(reference)
The following events for the period from June 2013 to late May 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) |
|
| – 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) |
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 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.
–"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 June 30 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, June 30, 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 June 24, there was a Mw7.9 earthquake under the Rat Islands,
Aleutian Islands. (Excerpted)":
According to the (United States) National Oceanic and Atmospheric Administration
(NOAA), small sea level variations considered as the tsunami caused by
this event were observed: 17cm at Amchitka, Aleutian Islands, 12 cm at
Atka, and 10cm at Kahului, Hawaii state. In the vicinity of this event,
a M8.3 earthquake occurred in 1906, and a M8.7 in 1965.
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: