May 12, 2010
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* There was no remarkable activity.
* On April 9, there was a M4.8 earthquake at a depth of approximately 55 km, off-shore of Kushiro. 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 April 26, there was a M5.1 earthquake at a depth of approximately 75km, off-shore of Miyagi prefecture. The focal mechanism had a tension axis in a NNW-SSE direction. This event occurred within the Pacific plate.
* On April 16, there was a M4.6 earthquake at a depth of approximately 10km in the Kaetsu region, Niigata prefecture. 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 April 26, there was a M6.6 earthquake off-shore south of Ishigakijima. The focal mechanism showed a strike-slip fault with a tension axis in a N-S direction. This event occurred within the Philippine Sea plate.
* On May 1, there was a M4.9 earthquake at a depth of approximately 10km in the Chuetsu 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.
* On May 3, there was a M6.1 earthquake under the ocean area near Torishima. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction.
May 12, 2010
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during April 2010.
(reference)
The following events for the period from April 2009 to the end of March 2010 have been listed as "Major Seismic Activity" in monthly "Evaluation of Seismic Activity"
| – 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 | |
| – 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 |
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 April 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 (Seismological and Volcanological Department, Japan Meteorological Agency, April 22, 2010)
"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
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."
– 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.
There is no supplementary information for the Kyushu-Okinawa region.
"On May 1, there was a M4.9 earthquake at a depth of approximately 10km in the Chuetsu region, Niigata prefecture. (excerpted)"
This event occurred at the place approximately 20km, in a northeastern direction, apart from the aftershock area of the 2004 Niigata Chuetsu Earthquake.
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: