| 10 July 2002 |
| Headquarters for Earthquake Research Promotion |
| Earthquake Research Committee |
Seismic Activity in June 2002
There was no remarkable activity. to supplementary reports
There was no remarkable activity. to supplementary reports
There was no remarkable activity. to supplementary reports
*On June 3, there was a deep M6.2 earthquake at a depth of approximately 520km under the ocean near Torishima. The focal mechanism had a compression axis that corresponds to the direction of the subducting Pacific plate. This event occurred within the Pacific plate.
*On June 14, there was a M4.9 earthquake at a depth of approximately 55km in southwestern Ibaraki prefecture, which caused minor damage. It is thought that this event occurred near the boundary between the Philippine Sea plate and the continental plate. The focal mechanism showed a reverse fault type with a compression axis in a NW-SE direction.
*On June 20, there was a M4.5 earthquake at a depth of approximately 45km in northeastern Chiba prefecture. It is thought that this event occurred near the boundary between the Pacific plate and the Philippine Sea plate. The focal mechanism showed a reverse fault with a nearly E-W compression axis.
*Seismic activity and crustal movements in the area from Miyakejima to Nijima-Kozushima have been continuing at a low level.
*The long-term changes that have been observed since last year in the continuous GPS data in the Tokai region, still appear to be continuing. to supplementary reports
There was no remarkable activity. to supplementary reports
There was no remarkable activity. to supplementary reports
On June 29, there was a deep M7.2 earthquake at a depth of approximately 590km near Vladivostok. The focal mechanism showed a compression axis downward toward the WNW. This event occurred within the Pacific plate.
*On July 1, there was a M4.3 earthquake at a depth of approximately 80km under the northern coast of Iwate prefecture.
| July 10, 2002 |
| Earthquake Research Committee |
57 earthquakes of M4.0 or greater occurred in Japan and the surrounding area during June. (57 events occurred in May, and an average of 46 earthquakes per month have occurred over the past thirty years through the end of 2000) 4 of these earthquakes were M5.0 or greater. (6 events of M5.0 or greater occurred in May)
Earthquakes of M6.0 or greater occurred, on average, 16 times a year during 1998 to 2000. (Over the past 30 years, on average, M6.0 or greater events have occurred approximately 16 times a year) There were 2 events of magnitude over M6.0 in June 2002 and a total of seven M6.0 or greater events so far this year.
The following regions have been noted as having significant seismic activity during the period from June 2001 to the end of May 2002.
| -Southern Iwate Prefecture | ||
| M6.4 on Dec. 2 2001 (depth of approximately 120km) | ||
| -Western Kanagawa Prefecture | M4.5 on Dec. 8 2001 (depth of approximately 25km) | |
| -Amami Oshima | M5.8 on Dec. 9 2001 (depth of approximately 40km) | |
| -Ocean area near Yonagunijima | M7.3 on Dec. 18 2001 (depth of approximately 10km) | |
| -Off-shore of Ibaraki prefecture | M5.5 on Feb. 12 2002 (depth of approximately 50km) | |
| -Ocean area south of Ishigakijima | M6.6 on Mar. 26 2002 (depth of approximately 10km) | |
| -Near Taiwan | M7.0 on Mar. 31, 2002 |
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 last year in the continuous GPS data of the Tokai region, still appear to be continuing.":
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 around April 2001. The trends have continued through June 2002 and show no signs of acceleration.
(This evaluation is in agreement with the views presented at the procedural meeting on June 24 of the Regional Assessment Committee for Strengthening Countermeasures against Earthquake Disaster. (see reference below))
(reference) "Recent seismic and crustal activity in the Tokai Region" (Japan Meteorological Agency, Department of Seismology and Volcanology, June 24 2002)
"Seismic activity within the Philippine Sea plate has declined since the cessation of the activity in central Shizuoka prefecture from April to June last year. Seismic activity within the crust, which was at normal or slightly higher levels last year, has returned to normal levels since the beginning of this year. According to the observations by the Geographical Survey Institute, there have been long-term changes in crustal movements in the Tokai region and its vicinity since last year. The activity appears to be continuing similar to the last few months. So far, there have been no changes of activity which are likely to be associated with the so-called Tokai earthquake."
There was additional activity in the Kanto-Chubu region as follows.
- Seismic activity occurred under Izu-Oshima Island and the surrounding area during June 5 and 6, with the largest event having a magnitude of M3.6.
There was additional activity in the Kinki-Chugoku-Shikoku region, as follows.
- Seismic activity at a depth of approximately 10km near the border of Wakayama and Nara prefectures that had declined since the beginning of May, increased temporarily since the middle of June. The activity was light and within an area that was previously active with the largest event M2.8.
There was additional activity in the Kyushu-Okinawa region as follows.
- On June 5, there was a M4.7 earthquake at a depth of approximately 50km under the sea near Miyakojima.
| 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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