March 8, 2006 Headquarters for Earthquake Research Promotion Earthquake Research Committee

	- 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)
	- Off-shore of Ibaraki prefecture	M6.3 on October 19, 2005 (depth approximately 50km)
	- Off-shore of Sanriku	M7.2 on November 15, 2005
		(see Supplementary Information 3)

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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 February 13, there was a M4.8 earthquake at a depth of approximately 10km in the Shonai region, Yamagata prefecture. The focal mechanism showed a reverse fault with a compression axis in an E-W direction.":
In this vicinity, small events have been occurring since November 2005. Although, the activity increased temporarily with the recent earthquake, seismicity has been gradually declining.

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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, appear to be slightly smaller recently.":
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, have been showing a trend of moderate change since about April 2001. This long-term change seems to be diminishing recently.
(This evaluation is in agreement with the views presented at the procedural meeting on February 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, February 27, 2006)

"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.
The long-term crustal movements from the slow slip at the plate boundary in the Tokai region and its neighboring area, seem to have slightly decreased recently."
In addition, there were strain changes and low frequency earthquakes observed in eastern Aichi prefecture during the period from January 16 through 22, which is thought to be caused by the short-term slow slip at the plate boundary. Similar activity was seen 21 times during the past 6 years. The latest was observed in July, 2005. "

There was additional activity in the Kanto - Chubu region, as follows.
- Light seismicity started off-shore east of the Izu Peninsula on February 19. In addition to the seismic activity, crustal movements were observed on tiltmeters and strainmeters in the surrounding area. According to the GPS data, there was a slight increase in baseline length observed during the period from January through February. The largest earthquake so far was a M2.8 event (maximum seismic intensity 2). Off-shore east of the Izu Peninsula, there was light seismic activity during the period from January 25 through 31.
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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

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

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3 Change in magnitude of the Earthquake Off-shore of Sanriku on November 15, 2005
After close examination, the magnitude of the Earthquake Off-shore of Sanriku on November 15, 2005, was modified to M7.2. The previous magnitude from the evaluation of "Seismic Activity for November 2005" was 7.1.

• Source Parameters of the Off-shore Sanriku Earthquake on November 15, 2005

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.