June 10, 2014
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On May 5, there was a magnitude (M) 6.0 earthquake under the ocean area near Izu-Oshima. This event caused the maximum seismic intensity 5 Lower observed at Tokyo Metropolitan, and damage with injured persons.
There was no remarkable activity.
There was no remarkable activity.
* On May 3, there was a M6.0 earthquake under the ocean area near Iwotou Island. The focal mechanism of this event had a tension axis in the dip direction of the Pacific plate. This event occurred within the subducting Pacific plate.
* On May 5, there was a M6.0 earthquake at a depth of approximately 160 km under the ocean area near Izu-Oshima. The focal mechanism of this event had a tension axis in the subducting direction of the Pacific plate. This event occurred within the Pacific plate.
* On May 13, there was a M4.9 earthquake at a depth of approximately 70 km under the northwestern Chiba prefecture. The focal mechanism showed a reverse fault type with a compression axis in a WNW-ESE 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.
Note: GNSS (Global Navigation Satellite System) is a general name of satellite positioning system such as GPS.
June 10, 2014
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during May 2014.
(reference)
The following events for the period from May 2013 to late April 2014 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities".
| – Offshore Fukushima Prefecture | M6.0 on May 18, 2013 (Depth of approximately 45 km) |
|
| – 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 |
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 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-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.
– From May 3 to 5, seismic activity became active in the area from Hida region, Gifu prefecture to the middle Nagano prefecture (near the border between Gifu and Nagano prefectures). In this period, 42 earthquakes with seismic intensity 1 or over occurred (maximum M3.9 earthquake on May 3 with maximum seismic intensity 3). There was a small-scale activity such as a M3.7 earthquake occurring on May 16 in the north side of this activity area. As a whole the activity has decreased and almost converged. In the vicinity of this area, active seismicity was observed from August to October in 1998, the earthquake of maximum M5.6 (maximum seismic intensity 4) occurring on August 16. In addition, seismic activity became active in March, 2011, after the occurrence of the 2011 off the Pacific Coast of Tohoku Earthquake, and there was a M4.8 earthquake (maximum seismic intensity 4) on March 21.
–"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 May 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, May 26, 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.
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: