January 13, 2017
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On December 28, there was a Magnitude (M) 6.3 earthquake in the northern Ibaraki prefecture. The maximum seismic intensity 6 Lower was observed in Ibaraki prefecture. This event caused some damage with injured persons.
There was no remarkable activity.
* In the activity area of a M7.4 earthquake, which occurred on November 22 in the continental crust offshore Fukushima prefecture, there were a M5.5 earthquake on December 20 and a M5.4 one on December 31: there were 4 earthquakes of M5.0 or over from December 1 until January 5. The seismic activity still continues, decaying as a whole.
* On December 24, there was a M5.1 earthquake at a depth of approximately 30 km (due to CMT solution), offshore Fukushima prefecture. The focal mechanism showed a normal fault type with a tension axis in an E-W direction.
* On December 6, there was a M5.5 earthquake at a depth of approximately 5 km in the Hida region, Gifu prefecture. The focal mechanism had a compression axis in an NW-SE direction. This event occurred within the crust.
* In the GNSS data for the Tokai region, there has been no change of activity which is likely to be associated with the Tokai earthquake.
There was no remarkable activity.
* In the ocean area near Tokara Islands (In the ocean area near Takarajima and Kodakarajima), the seismic activity became high after December 5, and there were 2 earthquakes with the maximum seismic intensity 4 and 55 ones with seismic intensity 1 or over until December 31. The maximum one is a M3.9 earthquake on December 21.
* On December 14, there was a M6.3 earthquake in the ocean area near Mariana Islands. Also there was a M6.5 one in the neighborhood of this event on December 22.
* On January 5, 2017, there was a M5.3 earthquake at a depth of approximately 55 km, offshore Fukushima prefecture. The focal mechanism showed a reverse fault type with a compression axis in an NW-SE direction.
Note: GNSS (Global Navigation Satellite System) is a general name of satellite positioning system such as GPS.
January 13, 2017
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during December 2016.
(reference)
The following events for the period from December 2015 to late November 2016 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities."
| – Sanpachi-Kamikita Region, Aomori Prefecture | M4.6 on January 11, 2016 (Depth of approximately 10 km) |
|
| – Offshore Urakawa | M6.7 on January 14, 2016 (Depth of approximately 50 km) |
|
| – Kumamoto Earthquakes | M6.5 on April 14, 2016 and M7.3 on April 16, 2016 (Depth of approximately 10 km) |
|
| – Southern Ibaraki Prefecture | M5.5 on May 16, 2016 (Depth of approximately 40 km) |
|
| – Uchiura Bay | M5.3 on June 16, 2016 (Depth of approximately 10 km) |
|
| – Northern Ibaraki Prefecture | M5.4 on July 27, 2016 (Depth of approximately 55 km) |
|
| – Kumamoto Region, Kumamoto Prefecture | M5.2 on August 31, 2016 (Depth of approximately 15 km) |
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| – Ocean Area near Okinawa Main Island | M5.6 on September 26 (Depth of approximately 45 km) |
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| – Central Tottori Prefecture | M6.6 on October 21, 2016 (Depth of approximately 10 km) |
|
| – Offshore Fukushima Prefecture | M7.4 on November 22, 2016 (Depth of approximately 10 km) |
There is no supplementary information for Hokkaido region.
There is no supplementary information for Tohoku region.
–"In the GNSS data for the Tokai region, there has been no change
of activity which is likely to be associated with the Tokai earthquake.":
(This evaluation is in agreement with the views presented at the regular
meeting on December 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, December 26, 2016)
"No change of activity which is likely to be associated with the Tokai earthquake has been observed until now. (Excerpted)"
– In the central Tottori prefecture where a M6.6 earthquake occurred on October 21, there were 2 earthquakes with maximum seismic intensity 3 (1 in November) and 18 earthquakes with seismic intensity 1 or over (33 in November) in December. The seismic activity still continues, decaying as a whole.
– Non-stationary crustal deformation surrounding the Bungo Channel observed from around December 2015 is now almost finished. This deformation is thought to be due to a slow slip (slow-slip) at the boundary between the Philippine Sea and the continental plates.
– In December, no earthquake with maximum seismic intensity 4 (1 in November) and 3 earthquakes with maximum seismic intensity 3 (1 in November) occurred in the Kumamoto and Aso regions, Kumamoto prefecture. A series of seismic activity of the 2016 Kumamoto Earthquakes in the Kumamoto and Aso regions is still continuing, decaying as a whole. According to the GNSS observation, postseismic deformation is still observed in the area centered on the series of the seismic activity.
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: