November 10, 2009
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
There was no remarkable activity.
* On October 10, there was a M5.1 earthquake at a depth of approximately 90km, off-shore of Urakawa. The focal mechanism had a compression axis in an E-W direction. This event occurred within the Pacific plate.
* On October 11, there was a M5.4 earthquake off-shore southeast of the Nemuro Peninsula. The focal mechanism showed a reverse fault with a compression axis in a NW-SE direction. It is thought that this event occurred at the boundary between the Pacific and the continental plates.
* On October 12, there was a M4.9 earthquake at a depth of approximately 5km in Aizu, Fukushima prefecture. The focal mechanism showed a normal fault with a tension axis in a NNE-SSW direction. This event occurred within the crust.
* Starting around October 6, there was seismic activity, with the largest event a M3.9 earthquake, at a depth of approximately 10km within the crust in southern Nagano prefecture. The determined focal mechanisms showed strike-slip faults with compression axes in E-W and WNW-ESE directions.
* On October 23, there was a M5.0 earthquake at a depth of approximately 45km off-shore of Ibaraki prefecture.
* On October 23, there was a M3.3 earthquake at a depth of approximately 10km in the Chuetsu Region, Niigata prefecture. The focal mechanism showed a strike-slip fault with a compression axis in a NNW-SSE direction. This event occurred within the crust.
* There have been no anomalous changes observed in the GPS data for the Tokai region.
There was no remarkable activity.
* On October 30, there was a M6.8 earthquake off-shore northeast of Amami Oshima. The focal mechanism showed a reverse fault with a compression axis in a NW-SE direction. It is thought that this event occurred at the boundary between the Philippine Sea and the continental plates. According to the GPS data, small crustal movements associated with this event were observed on the Satsunan Islands.
* On October 4, there was a M6.3 earthquake near Taiwan. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction.
* On November 4, there was a M5.6 earthquake off-shore west of the Ogasawara Islands [under the ocean area near Chichijima].
[ ] were the regional names of the epicenters used in the Japan Meteorological Agency announcement.
November 10, 2009
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during October 2009.
(reference)
The following regions have been noted as having major seismic activity during the period from October 2008 to the end of September 2009.
| – Under Suruga Bay | M6.5 on August 11, 2009 (depth of approximately 25km) | |
| – Off-shore East of Hachijojima | M6.6 on August 13, 2009 | |
| – Under the Ocean Area near Ishigakijima | M6.7, M6.6 on August 17, 2009 |
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 procedural meeting on October 26 of the Assessment Committee for Areas under Intensified Measures against Earthquake Disaster. (see reference below))
(reference) "Recent seismic and crustal activity in the Tokai region and its vicinity" (Seismological and Volcanological Department, Japan Meteorological Agency, October 26, 2009)
"So far, there have been no changes of activity which are likely to be associated with the so-called Tokai earthquake.
1. Status of seismicity
Within the crust under mid-western Shizuoka prefecture, general seismicity has been slightly strong since mid-2005.
There continue to be fewer events within the Philippine Sea plate under the region around Hamana lake.
In other regions, seismic activity is generally at a normal level.
In addition, deep low-frequency earthquakes occurred near the plate boundary under Aichi prefecture from September 30 through October 7. In this vicinity, there were deep low-frequency earthquakes observed in February, from mid-May through the beginning of June, and from the end of August through the beginning of September this year.
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.
In addition, there were crustal movements observed on the strainmeters in the neighboring regions from September 30 through October 3, which are thought to have been caused by the short-term slow slip around the plate boundary, and are concurrent with the deep low-frequency seismicity mentioned above. Crustal movements related to short-term slow slip were observed in February, from late May through the beginning of June, and from the end of August through the beginning of September this year."
There is no supplementary information for the Kinki - Chugoku - Shikoku region.
There is no supplementary information for the 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: