Aug. 10, 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)
	- Amakusa Ashikita region, Kumamoto prefecture	M4.8 on June 3, 2005 (depth approximately 10km)
	- Chuetsu region, Niigata prefecture	M5.0 on June 20, 2005 (depth approximately 15km)

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2 Nationwide Seismic Activity by Region

(1) Hokkaido Region

There is no supplementary information for the Hokkaido region.

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(2) Tohoku Region

"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. It is thought that this event occurred at the boundary between the Pacific and the continental plates.":
Seismic activity in the vicinity continued with some decreases and increases until July 13. However, the activity declined from then onwards, and subsided at the end of July.

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(3) Kanto-Chubu Region

"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.
In addition, during the period from July 20 to 23, slight crustal movements were observed on some strainmeters and tiltmeters in eastern Aichi prefecture and in western Shizuoka prefecture. This is thought to be due to a short-term slow slip in eastern Aichi prefecture. Also, at nearly the same time, relatively strong low-frequency earthquakes were observed in eastern Aichi prefecture. Movements such as these, observed on strainmeters and tiltmeters, along with simultaneous low-frequency earthquakes, occurred several times in 2004.
(This evaluation is in agreement with the views presented at the procedural meeting on July 25 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, July 25, 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.
In addition, during the period from July 20 to 23, there were slight changes observed on some strainmeters and tiltmeters. During this time, there were low-frequency earthquakes under eastern Aichi prefecture."

There was additional activity in the Kanto-Chubu region, as follows.
- On July 24, there was a M4.5 earthquake at a depth of approximately 65km under southern Chiba prefecture.
- Seismic activity increased off-shore east of Hachijojima (approximately 250km east of Hachijojima) since July 26. There were six earthquakes equal to or larger than M5.0 (the largest M5.5 on July 27). No event equal to or larger than M5.0 has occurred, so far, in August. The seismic activity has been declining.

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(4) Kinki-Chugoku-Shikoku Region

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

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(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.

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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.