December 9, 2010
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
There was no remarkable activity.
* On November 19, there was a M4.8 earthquake at a depth of approximately 55km, off-shore southeast of Nemuro Peninsula. 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.
There was no remarkable activity.
* On November 5, there was a M4.6 earthquake at a depth of approximately 45km under southern Ibaraki prefecture. The focal mechanism showed a reverse fault with a compression axis in a NW-SE direction. This event occurred at the boundary between the Philippine Sea and the continental plates.
* On November 24, there was a M4.9 earthquake at a depth of approximately 45km, off-shore of Ibaraki 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 November 30, there was a M7.1 earthquake at a depth of approximately 490km, off-shore west of Bonin Islands. The focal mechanism had a compression axis in a direction of subducting Pacific plate. This event occurred within the Pacific plate.
* There have been no anomalous changes observed in the GPS data for the Tokai region.
There was no remarkable activity.
There was no remarkable activity.
* On December 2, there was a M4.6 earthquake at a depth of approximately 5km in the central Ishikari region. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction. This event occurred within the crust.
* On December 6, there was a M5.8 earthquake off-shore east of Aomori prefecture.
December 9, 2010
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during November 2010.
(reference)
The following events for the period from November 2009 to the end of October 2010 have been listed as "Major Seismic Activity" in monthly "Evaluation of Seismic Activity".
| – Off-shore East of the Izu Peninsula | Seismic activity with M5.0 on December 17, M5.1 on December 18, 2009 |
|
| – 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 |
There is no supplementary information for the Hokkaido region.
There is no supplementary information for the Tohoku region.
"On November 30, there was a M7.1 earthquake at a depth of approximately
490km, off-shore west of Bonin Islands. (The rest is omitted.)":
Since the Pacific plate, which subducts from east to the west, efficiently
transmits seismic waves, the areas along the Pacific coast from the Tohoku
through the Kanto regions had stronger shaking. (Areas of anomalous seismic
intensity)
"There have been no anomalous changes observed in the GPS data for the Tokai region.":
(This evaluation is in agreement with the views (reference below) presented at the procedural meeting on November 22 of the Assessment Committee for Areas under Intensified Measures against Earthquake Disaster.)
(Reference) Recent seismic and crustal activity in the Tokai region and its vicinity (Seismological and Volcanological Department, Japan Meteorological Agency, November 22, 2010)
"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 was slightly strong since mid-2005 within the crust under mid-western Shizuoka prefecture, but it has tended to resume a normal level from around this spring.
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.
In addition, deep low-frequency earthquakes were observed near the plate boundary under Aichi to southern Nagano prefectures from November 11, and the activity has been continuing. In this vicinity, a sequence of deep low-frequency earthquakes was observed in late April through early May.
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, crustal movements were observed on the strainmeters in the neighboring regions from November 13, which are thought to have been caused by short-term slow slip around the plate boundary under Aichi prefecture, and were concurrent with the deep low-frequency seismicity mentioned above. Crustal movements related to short-term slow slip had not been observed since April this year."
– Non-stationary crustal movements near Bungo Strait, which had been seen since around autumn 2009 appear to be subsiding in general. It is thought that they were caused by slow slip at the boundary between the Philippine Sea and the continental plates.
There is no supplementary information for the Kyushu-Okinawa region.
"On December 2, there was a M4.6 earthquake at a depth of approximately 5km in the central Ishikari region. (The rest is omitted.)":
After this event, 6 earthquakes with seismic intensity 1 or over were observed
till December 7.
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: