November 10, 2010
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On October 3, there was a M4.7 earthquake in the Joetsu region, Niigata prefecture. This event had a maximum seismic intensity 5 Lower in Niigata prefecture.
* On October 4, there was a M6.4 earthquake under the ocean area near Miyakojima.
* On October 14, there was a M5.5 earthquake at a depth of approximately 55km under eastern Hidaka region [southern Tokachi region]. The focal mechanism showed a reverse fault with a compression axis in a NW-SE direction. This event occurred at the boundary between the Pacific and the continental plates.
* There was no remarkable activity.
* On October 3, there was a M4.7 earthquake at a depth of approximately 20km in the Joetsu region, Niigata prefecture. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction. This event occurred within the crust.
* There have been no anomalous changes observed in the GPS data for the Tokai region.
* On October 6, there was a M4.5 earthquake at a depth of approximately 5km in Tosa Bay. The focal mechanism showed a reverse fault with a compression axis in an ENE-WSW direction. This event occurred within the crust.
* On October 4, there was a M6.4 earthquake under the ocean area near Miyakojima. The focal mechanism had a compression axis in a NE-SW direction
* 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.
Note:[ ] was the regional name of the epicenter used in the Japan Meteorological
Agency announcement.
November 10, 2010
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during October 2010.
(reference)
The following events for the period from October 2009 to the end of September 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) |
There is no supplementary information for the Hokkaido region.
–In Nakadoori, Fukushima prefecture, there has been strong seismic activity with the largest M5.7 since around September 29. It has gradually been subsiding.
"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 October 25 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, October 25, 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, and it has tended to resume the 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.
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."
– Under the ocean area near Izu-Oshima, seismic activity was temporally brisk from evening of October 17th through the hour before dawn of 18th. The largest was a M3.1 earthquake on 17th. Under the ocean area near Izu-Oshima, recently there was the similar activity around February and July 2004, June 2006, and July 2007.
– Non-stationary crustal movements are still observed near Bungo Strait, which have been seen since around autumn 2009. It is thought that they have been caused by slow slip at the boundary between the Philippine Sea and the continental plates.
"On October 4, there was a M6.4 earthquake under the ocean area near Miyakojima. (Excerpted)":
The tsunami warning associated with this earthquake was issued, but no tsunami was observed. In the vicinity of this event, there was a M6.5 earthquake on August 5, 2009.
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: