Oct. 12, 2005 Headquarters for Earthquake Research Promotion Earthquake Research Committee

	- Off-shore southeast of the Kii Peninsula (Off-shore of Tokaido)
		M7.4 on September 5, 2004
	- Southern Ibaraki prefecture	M5.7 on October 6, 2004 (depth approximately 65km)
	- Ocean area near Yonaguni Island	M6.6 on October 15, 2004
	- Chuetsu region, Niigata prefecture (2004 Niigata Chuetsu Earthquake)
		M6.8 on October 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)
	- Northwestern Chiba prefecture	M6.0 on July 23, 2005 (depth approximately 75km)
	- Off-shore of Miyagi prefecture	M7.2 on August 16, 2005 (depth approximately 40km)
	- Chuetsu region, Niigata prefecture	M5.0 on August 21, 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

"The aftershock activity of the earthquake (M7.2) that occurred off-shore of Miyagi prefecture on August 16, has been continuing at a low level. The largest aftershock so far is a M4.7 event on September 12 that occurred near the main shock. According to the GPS data, small postseismic movements were observed following the main shock.":
According to the seafloor geodetic observations before and after the recent event, crustal movements were observed in an ENE direction at the observation station near the main shock. These data are consistent with the fault model that was estimated from the onshore GPS observation data

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(3) Kanto-Chubu Region

"On September 20, there was a M4.3 earthquake at a depth of approximately 70km under northwestern Chiba prefecture.":
In this vicinity, there was a M6.0 earthquake on July 23 (maximum seismic intensity 5 Upper).

"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 September 26 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, September 26, 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 this event 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. "

There was additional activity in the Kanto-Chubu region, as follows.
- Seismic activity increased off-shore east of Hachijojima (approximately 250km east of Hachijojima) from July 26. There have been no earthquakes larger than M4.0 since a M4.4 event on September 11. The seismic activity has been declining.

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(4) Kinki-Chugoku-Shikoku Region

- On September 4, there was a M4.3 earthquake at a depth of approximately 55km under Iyonada.

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(5) Kyushu-Okinawa Region

- There is no supplementary information for the Kyushu - Okinawa region.

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Supplement

*	Since August 27, weak seismicity started at a depth of approximately 10km in the Chikuhou region, Fukuoka prefecture. On October 2 the largest (M2.8) earthquake occurred. The seismic activity subsided by October 6.

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.