July 13, 2005 Headquarters for Earthquake Research Promotion Earthquake Research Committee

	- Off-shore of Iwate prefecture	M5.8 on August 10, 2004 (depth approximately 50km)
	- Off-shore southeast of the Kii Peninsula (Off-shore of Tokaido)
		M7.4 on September 5, 2004
	- Chuetsu region, Niigata prefecture (2004 Niigata Chuetsu Earthquake)
		M6.8 on Oct. 23, 2004 (depth approximately 10km)
	- Off-shore of Kushiro	M7.1 on November 29, 2004 (depth approximately 50km)
	- Southern Rumoi subprefecture	M6.1 on December 14, 2004 (depth approximately 10km)
	- Off-shore southeast of the Boso Peninsula (near the triple junction of the plates)
		M6.8 on January 19, 2005
	- Southern Ibaraki prefecture	M5.4 on February 16, 2005 (depth approximately 45km)
	- Off-shore west of Fukuoka prefecture	M7.0 on March 20, 2005 (depth approximately 10km)
	- Northeastern Chiba prefecture	M6.1 on April 11, 2005 (depth approximately 50km)

to the text

2 Nationwide Seismic Activity by Region

(1) Hokkaido Region

There is no supplementary information for the Hokkaido region.

to the text

(2) Tohoku Region

There is no supplementary information for the Tohoku region.

to the text

(3) Kanto-Chubu Region

"On June 20, there was a M5.6 earthquake at a depth of approximately 50km under northeastern Chiba prefecture. The focal mechanism showed a reverse fault with a compression axis in an E-W direction. It is thought that this event occurred at the boundary between the Philippine Sea plate and the Pacific plate.":
In this vicinity, there was a M6.1 earthquake on April 11, 2005, and since then the seismicity has been slightly increasing. A similar situation was seen after the M6.1 earthquake on June 3, 2000. At that time, slightly strong seismic activity continued for about four months until September 2000.

"The long-term changes that have been observed since 2001 in the continuous GPS data in the Tokai region, still appear to be continuing.":
According to the GPS data, the Pacific side of the Tokai-Chubu region maintained a steady rate with movement to the WNW, consistent with the subduction of the Philippine Sea plate toward the northwest. The results, from observations in the area centered on western Shizuoka prefecture, had been showing a trend of moderate change since about April 2001. Since the earthquakes off-shore, southeast of the Kii Peninsula on September 5, 2004, some changes appeared in the trends. However, the deformation has recently been returning to the trend before the earthquakes.
(This evaluation is in agreement with the views presented at the procedural meeting on June 27 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, June 27, 2005)

" So far, there have been no changes of activity which are likely to be associated with the so-called Tokai earthquake.
There was no remarkable seismic activity in general. The seismicity continues at a level lower than normal directly under Hamana lake. In other regions, seismic activity is generally at a normal level.
For the crustal movements, since the M7.4 earthquake off-shore of Tokaido (off-shore southeast of the Kii Peninsula) on September 5, 2004, postseismic movements associated with these events were observed. Recently the deformations have returned to the previous trend, and the long-term crustal movements from the slow slip at the plate boundary is continuing. "

"On June 20, there was a M4.6 earthquake at a depth of approximately 10km in mid-western Mino, Gifu prefecture. The focal mechanism showed a strike-slip fault with a compression axis in a WNW-ESE direction.":
The aftershock activity immediately after the event was relatively strong, however it has been recently subsiding. The largest aftershock so far was a M4.3 event that occurred on June 20.

There was additional activity in the Kanto-Chubu region, as follows.
- On June 5, there was a M3.3 earthquake at a depth of approximately 15km in the Chuetsu region, Niigata prefecture, which had a maximum seismic intensity 4. The aftershock activity subsided by June 15. This event was located approximately 20km north of the aftershock region of the 2004 Niigata Chuetsu Earthquake.

to the text

(4) Kinki-Chugoku-Shikoku Region

- There is no supplementary information for the Kinki - Chugoku - Shikoku region.

to the text

(5) Kyushu-Okinawa Region

- The aftershock activity of the earthquake off-shore west of Fukuoka prefecture on March 20 (M7.0), is continuing to decline.

to the text

Supplement

"On July 2, there was a M5.5 earthquake off-shore of Sanriku. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction.":
The seismic activity has been continuing near the epicenter, with the largest event, a M5.2 earthquake on June 6.

to the text

Reference 1 Earthquakes that are described in the "Evaluation of Seismic Activity"(Monthly Report of Seismic Activity in Japan) are events of M6.0 and greater, or events of M4.0 and greater (M5.0 or greater off-shore) that have maximum intensity of 3 or greater. Reference 2 Information that is described in the "Supplementary Information to the Evaluation" includes: 1) Reference information related to seismic activity described in the "Evaluation of Seismic Activity" 2) Recent earthquake activity over the past year related to the events described in "Major Seismic Activity" in the "Evaluation of Seismic Activity" 3) Seismic activity that has been evaluated, but not included in the "Evaluation of Seismic Activity" because it is within normal bounds and not prominent.