February 9, 20166
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On January 11, there was a magnitude (M) 4.6 earthquake in Sanpachi-Kamikita region, Aomori prefecture. Maximum seismic intensity 5 Lower was observed in Aomori prefecture.
* On January 14, there was a M6.7 earthquake offshore Urakawa. Maximum seismic intensity 5 Lower was observed in Hokkaido and Aomori prefectures. This event caused damage with injured persons and so on.
* On January 12, there was a M6.2 earthquake at a depth of approximately 270 km, offshore northwest of Hokkaido. The focal mechanism of this event had a tension axis in an NE-SW direction. This event occurred within the Pacific plate.
* On January 14, there was a M6.7 earthquake at a depth of approximately 50 km, offshore Urakawa. The focal mechanism 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. The result of the GNSS observation showed a small crustal deformation accompanying this event.
* On January 21, there was a M5.1 earthquake at a depth of approximately 50 km, offshore southeast of Nemuro peninsula. The focal mechanism of this event showed a reverse fault type with a compression axis in a WNW-ESE direction.
* On January 11, there was a M4.6 earthquake at a depth of approximately 10 km in Sanpachi-Kamikita region, Aomori prefecture. The focal mechanism of this event showed a reverse fault type with a compression axis in an ENE-WSW direction. This event occurred within the crust.
* On January 25, there was a M4.2 earthquake at a depth of approximately 30 km, offshore Fukushima prefecture. The focal mechanism of this event showed a normal fault type with a tension axis in an NNW-SSE direction. This event occurred within the continental plate.
* On January 6, there was a M6.0 earthquake at a depth of approximately 190 km under the ocean area near Iwotou Island. The focal mechanism of this event had a tension axis in an E-W direction. This event occurred within the Pacific plate.
* 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.
* On January 9, there was a M5.4 earthquake at a depth of approximately 30 km under the ocean area near Amami Oshima. The focal mechanism of this event showed a reverse fault type with a compression axis in an N-S direction.
* On February 2, there was a M5.6 earthquake at a depth of approximately 20 km, offshore Iwate prefecture. The focal mechanism of this event showed a normal fault type with a tension axis in an NNW-SSE direction.
* On February 5, there was a M4.6 earthquake at a depth of approximately 25 km in the eastern Kanagawa prefecture. The focal mechanism of this event had a compression axis in an NW-SE direction (preliminary).
* On February 6, there was a M6.4 earthquake near Taiwan. The focal mechanism of this event had a compression axis in an ENE-WSW direction (Geological Survey, United States of America (USGS)).
Note: [ ] is the regional name of the epicenter used in the announcement
of Japan Meteorological Agency.
GNSS (Global Navigation Satellite System) is a general name of satellite positioning system such as GPS.
February 9, 2016
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during January 2016.
(reference)
The following events for the period from January 2015 to late December, 2015 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities."
| – Southern Tokushima Prefecture | M5.1 on February 6, 2015 (Depth of approximately 10 km) |
|
| – Offshore Sanriku | M6.9 on February 17, 2015 | |
| – Offshore Iwate Prefecture | M5.7 on February 17, 2015 (Depth of approximately 50 km) |
|
| – Ocean Area near Yonagunijima | M6.8 on April 20 | |
| – Ocean Area near Torishima | M5.9 on May 3, 2015 | |
| – Offshore Miyagi Prefecture | M6.8 on May 13, 2015 (Depth of approximately 45 km) |
|
| – Ocean Area near Amami Oshima | M5.1 on May 22 (Depth of approximately 20 km) |
|
| – Northern Saitama Prefecture | M5.5 on May 25, 2015 (Depth of approximately 55 km) |
|
| – Offshore West of Ogasawara Islands | M8.1 on May 30 (Depth of approximately 680 km) |
|
| – Abashiri Region | M5.0 on June 4, 2015 (At a very shallow depth) |
|
| – Northern Inland of Iwate Prefecture | M5.7 on July 10, 2015 (Depth of approximately 90 km) |
|
| – Southern Oita Prefecture | M5.7 on July 13, 2015 (Depth of approximately 60 km) |
|
| – Tokyo Bay | M5.2 on September 12, 2015 (Depth of approximately 55 km) |
|
| – Central Coast of Chile | Mw8.3 on September 17, 2015 | |
| – Offshore West of the Satsuma Peninsula | M7.1 on November 14, 2015 |
There is no supplementary information for Hokkaido region.
–"On January 11, there was a M4.6 earthquake at a depth of approximately 10 km in Sanpachi-Kamikita region, Aomori prefecture. (Excerpted) " :
Afterwards, in the vicinity of the epicenter of this event, an aftershock activity such that 7 earthquakes with seismic intensity 1 or over have occurred until 25 is observed.
– Within the aftershock area of the Tohoku-Oki Earthquake, the number
of earthquakes of M4.0 or over, during one year from March 2012 (March
2012 - February 2013) became less than one fifth, during one year from
March 2013 (March 2013 - February 2014) became less than one tenth, and
during one year from March 2014 (March 2014 - February 2015) became less
than one fifteenth, of the number during about one year just after the
Tohoku-Oki Earthquake, and thus the aftershock activity has been decaying.
According to the GNSS data, crustal deformation which is thought to be post-seismic 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. Although both the horizontal and the vertical deformations were almost 1cm during the recent one month, the deformation has not yet returned to the state before 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 after four months, Mw8.5 after about two and a half years, Mw7.5 after about five and a half years, and Mw8.6 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.
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 fear that large earthquakes will occur from now on, and there is a possibility of strong shaking and high tsunami. It is necessary to pay attention continuously for it.
–"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 January 25 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, January 25, 2016)
"No change of activity which is likely to be associated with the Tokai earthquake has been observed until now. (Excerpted)"
– Non-stationary crustal deformation surrounding the Kii Channel observed from mid-2014 is still continuing. This deformation is thought to be due to a slow movement (slow-slip) at the boundary between the Philippine Sea and the continental plates.
There is no supplementary information for Kyushu region.
– A seismic activity is observed near the ocean area of Tokara Islands since February 3. 10 earthquakes with seismic intensity 1 or over have occurred until February 6. The maximum earthquake is a M2.7 one which occurred on February 3.
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: