| 14 July 2003 |
| Headquarters for Earthquake Research Promotion |
| Earthquake Research Committee |
Seismic Activity in June 2003
There was no remarkable activity. to supplementary reports
There was no remarkable activity. to supplementary reports
*The aftershock activity of the M7.0 earthquake that occurred at a depth of approximately 70km off-shore of Miyagi prefecture on May 26, continues with events on June 10 (M4.9) and on June 28 (M4.5) with a maximum seismic intensity 3, but overall the seismicity has been declining. The largest aftershocks so far were the events of M4.9 that occurred on May 27 and on June 10. According to the GPS data, no significant postseismic movement can be seen following the event on May 26. to supplementary reports
*On June 16, there was a M5.0 earthquake at a depth of approximately 75km off-shore of Ibaraki prefecture.
*On June 13, there was a M4.1 earthquake at a depth of approximately 10km near the border of Nagano and Gifu prefectures. Light seismic activity has been continuing in this vicinity since a M4.1 earthquake occurred on April 1.
*On June 5, there was a M4.2 earthquake at a depth of approximately 10km in the Kaga region of Ishikawa prefecture.
*The long-term changes that have been observed since 2001 in the continuous GPS data in the Tokai region, still appear to be continuing, although the rates seem smaller compared to 2001. to supplementary reports
There was no remarkable activity. to supplementary reports
There was no remarkable activity. to supplementary reports
*There was a M6.0 earthquake on June 9, and a M6.2 earthquake on June 10 near Taiwan.
*On July 3, there was a M5.8 earthquake at a depth of approximately 30km 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 July 9, there was a M4.3 earthquake at a depth of approximately 15km near the Chita Peninsula.
*On July 10, there was a M5.2 earthquake at a depth of approximately 60km under the ocean near Amami Oshima.
*On July 11, there was a M4.1 earthquake at a depth of approximately 20 km in western Kanagawa prefecture.
| July 14, 2003 |
| Earthquake Research Committee |
73 earthquakes of M4.0 or greater occurred in Japan and the surrounding area during June (99 events occurred in May, and an average of 46 earthquakes per month have occurred over the past thirty years through the end of 2000). 17 of the events were aftershocks of the earthquake that occurred off-shore of Miyagi prefecture on May 26 (In May, 59 of the events were part of this aftershock activity). 8 of these earthquakes in June were M5.0 or greater. (3 events of M5.0 or greater occurred in May.)
Earthquakes of M6.0 or greater occurred, on average, 15 times a year during 1998 to 2002. (Over the past 30 years through the end of 2000, on average, M6.0 or greater events have occurred approximately 16 times a year) There were 2 events of magnitude equal to or over M6.0 in June 2003, and there has been a total of 2 M6.0 or greater event by the end of May this year.
The following regions have been noted as having significant seismic activity during the period from June 2002 to the end of May 2003.
| -Ocean area east of Aomori prefecture | M5.9 on Oct. 14, 2002 (depth of approximately 50km) | |
| -Off-shore of Miyagi prefecture | M6.1 on Nov. 3, 2002 (depth of approximately 45km) | |
| -Hyuganada | M5.7 on Nov. 4, 2002 (depth of approximately 35km) | |
| -Off-shore of Miyagi prefecture | M7.0 on May. 26, 2003 (depth of approximately 70km) |
There is no supplementary information for the Hokkaido region.
There is no supplementary information for the Tohoku 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, although the rates seem smaller compared to 2001".
The Pacific side of the Tokai-Chubu region maintains a steady rate with movement to the WNW, consistent with the subduction of the Philippine Sea plate toward the northwest. The results from GPS observations in the area centered on western Shizuoka prefecture, have been showing a trend of moderate change since about April 2001. The trends have continued through June 2003, but the changes are becoming smaller compared to 2001.
(This evaluation is in agreement with the views presented at the procedural meeting on June 23 of the Regional Assessment Committee for Strengthening Countermeasures 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 23, 2003)
"So far, there have been no changes of activity which are likely to be associated with the so-called Tokai earthquake.
Although the seismicity directly under Hamana lake was declining, recently it has been increasing again. In the other regions, no remarkable changes of the seismic activity can be seen.
The long-term changes in crustal movements in the Tokai region and its vicinity caused by the slow slip on the plate boundary, have been continuing, although recently the rates seem smaller compared to 2001."
There is no supplementary information for the Kinki-Chugoku-Shikoku region.
- On June 25, there was a M3.8 earthquake at a depth of approximately 10km in central Oita prefecture (near Beppu). The seismic activity increased temporarily, and 5 earthquakes with maximum seismic intensity 1 or greater occurred, which includes this largest event (maximum seismic intensity 3). However, the seismicity subsided by the end of June. This type of light seismic activity is commonly seen in this vicinity.
| 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:
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