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June 13, 2007 |
| * | There was no remarkable activity. to supplementary reports |
| * | There was no remarkable activity. to supplementary reports | |
| * | On May 19, there was a M5.3 earthquake at a depth of approximately 65km off-shore east of Aomori prefecture [off-shore of Urakawa]. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE. This earthquake occurred at the boundary between the Pacific and the continental plates. to supplementary reports |
| * | On May 8, there was a M4.5 earthquake at a depth of approximately 45km under southern Ibaraki prefecture. The focal mechanism showed a reverse fault with a compression axis in a NW-SE direction. This event occurred at the boundary between the Philippine Sea and the continental plates. | |
| * | The aftershock activity of the Noto Hanto Earthquake on March 25 (Noto Hanto Earthquake in 2007) has been declining on the whole, although there was a M4.7 event on the northeastern side of the aftershock area on May 2, and a M5.0 event near the main shock on June 11. | |
| * | There is an active fault off the west coast of the Noto peninsula, which is a reverse fault trending in a NE-SW direction with a southeast dip. The preliminary results of an ocean bottom topographic survey have revealed that there is steep slope topography corresponding to that fault. The results of the ocean-bottom and onshore seismic observations have shown that the fault is located on the extension of the aftershock distribution. According to the slip distribution that was obtained from the crustal movement observations by the advanced land observing satellite, "Daichi", the recent earthquake is considered to be associated with the fault. | |
| * | There have been no anomalous changes observed in the GPS data for the Tokai region. to supplementary reports | |
| * | On May 13, there was a M4.6 earthquake at a depth of approximately 10km near the border between Shimane and Hiroshima prefectures [northern Hiroshima prefecture]. The focal mechanism showed a strike-slip fault with a compression axis in a WNW-ESE direction. This event occurred within the crust. to supplementary reports | |
| * | On May 7, there was a M5.1 earthquake at a depth of approximately 50km near Yakushima [under the ocean near Tanegashima]. to supplementary reports |
| * | On June 1, there was a M4.5 earthquake at a depth of approximately 60km under northern Saitama prefecture. The focal mechanism showed a strike-slip fault with a compression axis in a NNW-SSE direction. This event occurred within the Philippine Sea plate. |
| * | On June 1, there was a M4.3 earthquake at a depth of approximately 15km in western Shizuoka prefecture. The focal mechanism showed a strike-slip fault with a compression axis in a WNW-ESE direction. This event occurred within the crust. |
| * | On June 2, there was a M4.6 earthquake at a depth of approximately 50km under southern Ibaraki prefecture. The focal mechanism showed a reverse fault with a compression axis in a NW-SE direction. This event occurred at the boundary between the Philippine Sea and the continental plates. |
| * | On June 6, there was a sequence of seismicity with the largest event a M4.9 earthquake in central Oita prefecture. The focal mechanism of the largest earthquake (M4.9) showed a normal fault with a strike-slip component which had a tension axis in a N-S direction. This event occurred within the crust. The seismic activity was strong at first, and has been declining at present. to supplementary reports |
[ ] were the regional names of the epicenters used in the Japan Meteorological Agency announcement.
June 13, 2007
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during May 2007.
| M4.0 or greater: 81 (145 events occurred in April) | |
| M5.0 or greater: 11 (35 events occurred in April) | |
| M6.0 or greater: 0 (There has been a total of 7 events for 2007 by the end of May.) |
(reference)
| M4.0 or greater: 73 / month | (Median number of earthquakes over the past 10 years from 1996 through 2005) | |
| M5.0 or greater: 9 / month | (Median number of earthquakes over the past 30 years from 1976 through 2005) | |
| M6.0 or greater: 1.4 / month, approximately 17 / year | (Average number of earthquakes over the past 80 years from 1926 through 2005) |
The following regions have been noted as having significant seismic activity during the period from May 2006 to the end of April 2007.
| - Central Oita prefecture | M6.2 on June 12, 2006 (depth approximately 150km) | |
| - Off-shore east of the Chishima Islands | M7.9 on November 15, 2006 | |
| - Off-shore east of the Chishima Islands | M8.2 on January 13, 2007 | |
| - Noto Hanto Earthquake | M6.9 on March 25, 2007 (depth approximately 10km) | |
| - Central Mie prefecture | M5.4 on April 15, 2007 (depth approximately 15km) | |
| - Off-shore northwest of Miyakojima | seismic activity with M6.3, M6.7, M6.1 on April 20, 2007 |
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 April 23 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, May 28, 2007)
"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 remains at a level lower than normal directly under the area from eastern Hamana Lake through central Shizuoka prefecture. 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."
- The aftershock activity associated with a M5.4 earthquake that occurred in central Mie prefecture on April 15, has been declining.
There is no supplementary information for the Kinki - Chugoku - Shikoku region.
- According to the GPS data, slight crustal movements were observed on the Sakishima Islands associated with a sequence of seismicity off-shore northwest of Miyakojima, with the largest event a M6.7 earthquake on April 20.
"On June 6, there was a sequence of seismicity in central Oita prefecture with the largest event a M4.9 earthquake. The focal mechanism of the largest earthquake (M4.9) showed a normal fault with a strike-slip component and had a tension axis in a N-S direction. This event occurred within the crust. The seismic activity was strong at first, and has been declining at present."
In the area near this event, there was a sequence of seismicity with the largest event a M4.2 in April 2000. In addition, seismic activity lasting 2 or 3 days sometimes occurs. Also, the Beppu - Haneyama Fault Zone is located in this vicinity.
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Reference 1 Earthquakes that are described in the "Evaluation of Seismic Activity" (Monthly Report of Seismic Activity in Japan) have the following features. 1) Events of M6.0 and greater, or events that have maximum seismic intensity 4 or greater 2) Onshore events of M4.5 and greater that have maximum seismic intensity 3 or greater 3) Events under the ocean areas of M5.0 or greater that have maximum seismic intensity 3 or greater |
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| Reference 2 Information that is described in the "Supplementary Information to the Evaluation" includes: |
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| 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 |