February 9, 2011
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* There was no remarkable activity.
* There was no remarkable activity.
* There was no remarkable activity.
* On January 3, there was a M4.7 earthquake at a depth of approximately 10 km, off-shore of the Kaetsu region, Niigata prefecture. The focal mechanism showed a reverse fault with a compression axis in a NW-SE direction.
* On January 10, there was a M6.0 earthquake under the ocean area near Iwotou Island. The focal mechanism had a tension axis in an ENE-WSW direction.
* On January 13, there was a M6.3 earthquake at a depth of approximately 520 km, off-shore west of Bonin Islands. The focal mechanism had a compression axis in a direction of the subducting Pacific plate. This event occurred within the Pacific plate.
* On January 31, there was a M4.2 earthquake at a depth of approximately 10 km under the ocean area near Izu-Oshima. The focal mechanism showed a strike-slip fault with a compression axis in a NW-SE direction.
* There have been no anomalous changes observed in the GPS data for the Tokai region.
* On January 16, there was a M4.5 earthquake at a depth of approximately 45 km under northern Tokushima prefecture. The focal mechanism showed a strike-slip fault with a compression axis in a NNE-SSW direction. This event occurred within the Philippine Sea plate.
* There was no remarkable activity.
* On February 4, there was a M5.0 earthquake off-shore northeast of Amami-Oshima. The focal mechanism had a tension axis in an E-W direction.
* On February 5, there was a M5.2 earthquake at a depth of approximately 65 km, off-shore southeast of Chiba prefecture. The focal mechanism showed a strike-slip fault with a compression axis in an ENE-WSW direction.
February 9, 2011
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during January 2011.
(reference)
The following events for the period from January 2010 to the end of December 2010 have been listed as "Major Seismic Activity" in monthly "Evaluation of Seismic Activity"
| – Under the Ocean Area near Ishigakijima | M6.5 on February 7, 2010 | |
| – Under the Ocean Area near the Okinawa Main Island | M7.2 on February 27, 2010 | |
| – Along the Central Coast of Chile | Mw8.8 on February 27, 2010 | |
| – Off-shore of Fukushima Prefecture | M6.7 on March 14, 2010 (Depth of approximately 40km) |
|
| – Off-shore of Fukushima Prefecture | M6.2 on June 13, 2010 (Depth of approximately 40km) |
|
| – Northeastern Chiba Prefecture | M5.0 on July 23, 2010 (Depth of approximately 35km) |
|
| |
– Joetsu Region, Niigata Prefecture | M4.7 on October 3, 2010 (Depth of approximately 20km) |
| – Under the Ocean near Miyakojima | M6.4 on October 4, 2010 | |
| |
– Under the Ocean near Chichijima | M7.4 on December 22, 2010 |
There is no supplementary information for the Hokkaido region.
There is no supplementary information for the Tohoku region.
"There have been no anomalous changes observed in the GPS data for the Tokai region.":
(This evaluation is in agreement with the views presented at the regular
meeting on January 24 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 24, 2011)
"So far, there have been no changes of activity which are likely to be associated with the Tokai earthquake
1. Status of seismicity
General seismicity has been slightly strong since mid-2005 within the crust under mid-western Shizuoka prefecture.
There continue to be fewer events within the Philippine Sea plate under the region around Hamanako.
In other regions, seismic activity is generally at a normal level.
2. Status of crustal movements
There have been no remarkable changes observed over the entire region.
According to the GPS data and leveling results, the trend of long-term subsidence at Omaezaki has been continuing as before."
There is no supplementary information for the Kinki-Chugoku-Shikoku region.
There is no supplementary information for the Kyushu-Okinawa region.
The numbers of earthquakes with M4.0 or over and M5.0 or over in December 2010 were 213 and 27, respectively, in the Evaluation of Seismic Activity for December 2010, but as a result of close inspection, they are revised to be 232 and 28, respectively.
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: