January 9, 2009
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
There was no remarkable activity. to supplementary reports
There was no remarkable activity. to supplementary reports
* On December 15, there was a M5.2 earthquake off-shore of Sanriku (near the trench axis). It is thought that this event occurred within the Pacific plate. The focal mechanism showed a reverse fault with a compression axis in a NE-SW direction.
* On December 4, there was a M6.1 earthquake off-shore of Sanriku. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction. This event occurred at the boundary between the Pacific and the continental plates. Subsequently, there were M5.5 events on December 4, 6, 18. Although seismic activity increased temporarily, it has been declining.
* On December 7, there was a M4.3 earthquake at a depth of approximately 15km in central Miyagi prefecture. The focal mechanism showed a reverse fault with a compression axis in an E-W direction. This event occurred within the crust. to supplementary reports
* On December 20, there was a M6.6 earthquake off-shore east of the Kanto region. This event occurred near the boundary between the Pacific and the continental plates. The focal mechanism showed a reverse fault with a compression axis in an E-W direction. Associated with this event, small tsunamis were observed on the Pacific coast in Iwate and Miyagi prefectures. Subsequently, seismicity increased with a M6.2 earthquake on December 21. However, aftershocks have been presently subsiding.
* There have been no anomalous changes observed in the GPS data for the Tokai region. to supplementary reports
There was no remarkable activity. to supplementary reports
There was no remarkable activity. to supplementary reports
* On January 3, there was a M4.8 earthquake at a depth of approximately 50km off-shore of Fukushima prefecture. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction. This event occurred at the boundary between the Pacific and the continental plates.
* On January 4, at 04:43 (JST) there was a M7.6 earthquake near New Guinea. Associated with this earthquake, tsunamis were observed on the Izu and Ogasawara Islands, Nansei Islands and the Pacific coast from the Kanto region through the Kyushu region. There were tsunami heights of 0.4m on Chichijima and in Kushimoto-cho, Wakayama prefecture. Also at 07:33 (JST) on the same day, there was a M7.4 event at nearly the same location.
January 9, 2009
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during December 2008.
(reference)
The following regions have been noted as having major seismic activity during the period from December 2007 to the end of November 2008.
| - Noto region, Ishikawa prefecture | M4.8 on January 26, 2008 (depth approximately 10km) | |
| - Off-shore of Ibaraki prefecture | M7.0 on May 8, 2008 | |
| - Iwate-Miyagi Nairiku Earthquake in 2008 | M7.2 on June 14, 2008 (depth approximately 10km) | |
| - Off-shore of Ibaraki prefecture | M5.2 on July 5, 2008 (depth approximately 50km) | |
| - Near Okinoerabujima | M6.1 on July 8, 2008 (depth approximately 45km) | |
| - Off-shore of Fukushima prefecture | M6.9 on July 19, 2008 | |
| - Central Iwate prefecture | M6.8 on July 24, 2008 (depth approximately 110km) |
|
| - Off-shore of Tokachi | M7.1 on September 11, 2008 |
There is no supplementary information for the Hokkaido region.
"On December 7, there was a M4.3 earthquake at a depth of approximately
15km in central Miyagi prefecture. (excerpted)":
This event occurred within the aftershock region of the M6.4 earthquake (maximum seismic intensity 6 Upper) on July 26, 2003.
"On December 20, there was a M6.6 earthquake off-shore east of the Kanto region. (excerpted)":
In the announcement by Japan Meteorological Agency, the earthquake on December 20 (M6.6) occurred off-shore east of the Kanto region, and the event on December 21 (M6.2) occurred off-shore of Fukushima prefecture.
"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 December 22 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" (Japan Meteorological Agency, Department of Seismology and Volcanology, December 22, 2008)
"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
There was no remarkable seismic activity in general.
There are continued less frequent occurrences of events equal to or larger than M3.5 within the Philippine Sea plate under mid-western Shizuoka prefecture. However, when considering smaller events as well, seismic activity has increased. Also, there are continued fewer events within the Philippine Sea plate under the region around Hamana lake. On the other hand, seismicity has been continuing to be slightly strong within the crust in mid-western Shizuoka prefecture. In other regions, seismic activity is generally at a normal level.
2. Status of crustal movements
There were no notable changes observed in general.
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.
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: