November 12, 2014
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
There was no remarkable activity.
There was no remarkable activity.
* On October 3, there was a magnitude (M) 5.7 earthquake at a depth of approximately 30 km, offshore Iwate prefecture. The focal mechanisms of this event showed a reverse fault type with a compression axis in a WNW-ESE direction. This event occurred at the boundary between the Pacific and the continental plates.
* On October 11 at 11:35, there was a M6.1 earthquake offshore east of Aomori prefecture. In addition, on the same day at 14:20, there was a M5.6 earthquake at almost the same place. The focal mechanisms of these events showed a reverse fault type with a compression axis in a WNW-ESE direction. These events occurred at the boundary between the Pacific and the continental plates.
* On October 15, there was a M4.6 earthquake at a depth of approximately 65 km, offshore Miyagi prefecture. The focal mechanism had a compression axis in an E-W 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.
* On October 15, there was a M5.1 earthquake at a depth of approximately 45 km under the ocean near Okinawa Main Island. The focal mechanism of this event showed a reverse fault type with a compression axis in an NW-SE direction. This event occurred at the boundary between the Philippine Sea and the continental plates.
* On October 22, there was a M5.6 earthquake at a depth of approximately 50 km under the ocean near Okinawa Main Island (near Okinoerabujima). The focal mechanism of this event showed a reverse fault type with a compression axis in an NW-SE direction. This event occurred at the boundary between the Philippine Sea and the continental plates.
* On November 3, there was a M4.6 earthquake at a depth of approximately 30 km, offshore Tomakomai [Middle-eastern Iburi region]. The focal mechanisms of this event had a compression axis in an NE-SW direction. This event occurred in 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.
November 12, 2014
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during October 2014.
(reference)
The following events for the period from October 2013 to late September 2014 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities".
| – 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) |
|
| – Rat Islands, Aleutian Islands | Mw7.9 on June 24, 2014 | |
| – Offshore IwatePrefecture | M5.9 on July 5, 2014 (Depth of approximately 50 km) |
|
| – Middle Eastern Iburi Region | M5.6 on July 8, 2014 (Depth of approximately 5 km) |
|
| – Offshore Fukushima Prefecture | M7.0 on July 12, 2014 | |
| – Offshore East of Aomori Prefecture | M6.1 on August 10, 2014 (Depth of approximately 50 km) |
|
| – Northern Tochigi Prefecture | M 5.1 on September 3, 2014 (Depth of approximately 5 km) |
|
| – Southern Ibaraki Prefecture | M 5.6 on September 16, 2014 (Depth of approximately 45 km) |
There is no supplementary information for Hokkaido region.
There is no supplementary information for 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 October 27 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, October 27, 2014)
"No changes of activity which are likely to be associated with the Tokai earthquake have been observed until now. (Excerpted)"
– According to the GNSS data, non-stationary crustal deformation was observed around the Bungo strait. This deformation is considered to be caused by the gradual slip (slow-slip) at the boundary between the Philippine Sea and the continental plates. The deformation began in the summer of 2014. In addition, the slow-slip was observed in 1997, from 2003 to 2004, and from 2009 to 2010 around here.
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: