August 11, 2008
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On July 24, there was a M6.8 earthquake under central Iwate prefecture [under the northern coastal region in Iwate prefecture]. This event had a maximum seismic intensity 6 Upper in Iwate prefecture. (see the 186th Evaluation of the Earthquake Research Committee "Earthquake under Central Iwate Prefecture on July 24, 2008") This event caused damage with one fatality and approximately 200 injured people.
* On July 19, there was a M6.9 earthquake off-shore of Fukushima prefecture, which caused tsunamis observed on the Pacific coast in the Tohoku region.
* On July 5, there was a M5.2 earthquake off-shore of Ibaraki prefecture. This event had a maximum seismic intensity 5 Lower in Ibaraki prefecture.
* On July 8, there was a M6.1 earthquake near Okinoerabujima [under the ocean area near the Okinawa Main Island]. This event had a maximum seismic intensity 5 Lower in Kagoshima prefecture. to supplementary reports
* On July 6, there was a M6.1 earthquake near Urup Island [Chishima Islands]. to supplementary reports
* On July 24, at 00:26 (JST) there was a M6.8 earthquake at a depth of approximately 110km under central Iwate prefecture [under the northern coastal region in Iwate prefecture]. The focal mechanism had a tension axis in the direction of the subducting Pacific plate. This event occurred at an intermediate deep location within the Pacific plate (in the lower surface of the double seismic zone). The aftershock activity was at a low level. The largest aftershock so far was a M4.8 event that occurred at 11:27 on July 24 (maximum seismic intensity 3). According to the GPS data, there have been no remarkable crustal movements observed before and after this event.
* On July 19, there was a M6.9 earthquake off-shore of Fukushima prefecture. 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. This event caused tsunamis observed on the Pacific coast in the Tohoku region, with a tsunami height of 0.2m in Ayukawa, Ishinomaki city. Seismic activity was a main shock-aftershock sequence, and has been gradually declining. The largest aftershock so far was a M6.1 event on July 21. According to the GPS data, small crustal movements associated with the main shock were observed centered on the Pacific coast in Miyagi and Fukushima prefectures.
* Aftershock activity of the Iwate-Miyagi Nairiku Earthquake in 2008 on June 14 is generally on a declining trend, although on July 29 there was a M4.6 earthquake near the main shock. GPS monitoring shows that postseismic movement centered on the focal region has been continuing. to supplementary reports
* On July 5, there was a M5.2 earthquake at a depth of approximately 50km off-shore of Ibaraki prefecture. 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 21, there was a M6.4 earthquake at a depth of approximately 490km off-shore west of the Ogasawara Islands. The focal mechanism had a compression axis in the direction of the subducting Pacific plate. This event occurred within the Pacific plate.
* There have been no anomalous changes observed in the GPS data for the Tokai region. to supplementary reports
There was no remarkable activity. to supplementary reports
* On July 8, there was a M6.1 earthquake at a depth of approximately 45km near Okinoerabujima [under the ocean area near the Okinawa Main Island]. The focal mechanism showed a reverse fault with a compression axis in a NW-SE direction. This event occurred near the boundary between the Philippine Sea and the continental plates. to supplementary reports
* On July 13, there was a M6.1 earthquake under the northern Philippines.
* On August 8, there was a M4.6 earthquake at a depth of approximately 30km near the border between Tokyo and Kanagawa prefecture [in eastern Tama, Tokyo]. The focal mechanism showed a reverse fault with a compression axis in a N-S direction. This event is related to the subduction of the Philippine Sea plate.
* On August 9, there was a M5.4 earthquake at a depth of approximately 50km off-shore east of Aomori prefecture.
[ ] was the regional name of the epicenter used in the Japan Meteorological Agency announcement.
August 11, 2008
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during July 2008.
(reference)
The following regions have been noted as having major seismic activity during the period from July 2007 to the end of June 2008.
| - Niigataken Chuetsu-oki Earthquake in 2007 | M6.8 on July 16, 2007 (depth approximately 10km) | |
| - Off-shore west of Sakhalin | M6.4 on August 2, 2007 | |
| - Near the coastal area of Kujukurihama | seismic activity with M5.3 on August 16, and M4.8 on August 18, 2007 | |
| - Coast of Peru | M8.0 on August 16, 2007 | |
| - Western Kanagawa prefecture | M4.9 on October 1, 2007 (depth approximately 15km) | |
| - Noto region, Ishikawa prefecture | M4.8 on January 26, 2008 (depth approximately 10km) | |
| - Off-shore of Ibaraki prefecture | M7.0 on May 8, 2008 | |
| - Iwate-Miyagi Nairiku Earthquake in 2008 | M7.2 on June 14, 2008 (depth approximately 10km) |
There is no supplementary information for the Hokkaido region.
There is no supplementary information for the Tohoku region.
"There have been no anomalous changes observed in the GPS data for the Tokai region.":
(This evaluation is in agreement with the views presented at the procedural meeting on July 28 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 28, 2008)
"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. Under central Shizuoka prefecture, the seismicity remains at a level lower than normal within the plate. In other regions, seismic activity is generally at a normal level.
There were no notable changes observed in crustal movements in the Tokai region and its neighboring areas."
- On July 15, there were M4.1 and M4.3 earthquakes at a depth of approximately 20km in the Fujigoko area, eastern Yamanashi prefecture. Both focal mechanisms showed a reverse fault with a compression axis in a NW-SE direction. These events were related to the subduction of the Philippine Sea plate.
There is no supplementary information for the Kinki-Chugoku-Shikoku region.
There is no supplementary information for the Kyushu-Okinawa region.
Reference 1
Earthquakes that are described in the "Evaluation of Seismic Activity" (Monthly Report of Seismic Activity in Japan) have the following features.
Reference 2
Information that is described in the "Supplementary Information to the Evaluation" includes: