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December 13, 2006 |
| On November 15, there was a M7.9 earthquake off-shore east of the Chishima Islands. This event caused tsunamis from the coast of the Okhotsk Sea and along the whole Pacific coast (of Japan). to supplementary reports |
| * | On November 1, there was a M4.8 earthquake at a depth of approximately 50km under southern Tokachi subprefecture. The focal mechanism showed a reverse fault with a compression axis in a NW-SE direction. This event occurred at the boundary between the Pacific and the continental plates. Also, there was a M4.3 earthquake at nearly the same location on the same day. | |
| * | On November 22, there was a M5.6 earthquake at a depth of approximately 95km off-shore east of Hokkaido [near Kunashiri Island]. The focal mechanism had a tension axis in a N-S direction. This event occurred within the Pacific plate. to supplementary reports | |
| * | On November 30, there was a M4.3 earthquake at a depth of approximately 5km in Aizu, Fukushima prefecture.to supplementary reports |
| * | On November 24, there was a M4.3 earthquake at a depth of approximately 5km off-shore east of the Izu Peninsula. | |
| * | There have been no anomalous changes observed in the GPS data for the Tokai region. | |
| * | On November 19, there was a M4.2 earthquake at a depth of approximately 40km under Nanyo, Ehime prefecture. to supplementary reports |
| * | On November 18, there was a M6.0 earthquake under the ocean near Amami Oshima. The focal mechanism showed a reverse fault with a compression axis in a NW-SE direction. According to the GPS data, slight movements related to this earthquake were observed on Kikaijima. to supplementary reports |
| * | On November 15, 2006, at 20:14 (JST) there was a M7.9 earthquake (maximum seismic intensity 2) off-shore east of the Chishima Islands. The focal mechanism showed a reverse fault with a compression axis in a NW-SE direction. It is thought that this event occurred on the plate boundary. According to the GPS data, subtle movements related to this event were observed in northern Hokkaido. to supplementary reports |
| * | On December 4, there was a M4.5 earthquake at a depth of approximately 50km under northeastern Chiba 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 Philippine Sea and the Pacific plates. |
| * | On December 6, there was a M5.0 earthquake at a depth of approximately 30km off-shore of Kushiro. |
| * | On December 11, there was a M5.7 earthquake off-shore northeast of Amami Oshima. to supplementary reports |
[ ] was the regional name of the epicenter used in the Japan Meteorological Agency announcement.
December 13, 2006
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during November 2006.
| M4.0 or greater: 109 (101 events occurred in October) | |
| M5.0 or greater: 34 (26 events occurred in October) | |
| M6.0 or greater: 4 (There have been a total of 20 events for 2006 by the end of November.) |
(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 November 2005 to the end of October 2006.
| - Off-shore of Sanriku | M7.2 on November 15, 2005 |
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| - Hyuganada | M5.5 on March 27, 2006(depth approximately 35km) | |
| - Off-shore east of the Izu Peninsula | seismic activity with M5.8 on April 21 and M4.5 on April 30, 2006 |
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| - Central Oita prefecture | M6.2 on June 12, 2006(depth approximately 150km) |
There is no supplementary information for the Hokkaido region.
"On November 30, there was a M4.3 earthquake at a depth of approximately 5km in Aizu, Fukushima prefecture.":
The aftershock activity immediately after the earthquake was comparatively strong. It has mostly subsided at present.
- The postseismic movements that were observed at the GPS stations around the Oshika Peninsula after the earthquake off-shore of Miyagi prefecture on August 16, 2005 (M7.2, maximum seismic intensity 6 Lower), have mostly subsided.
"On November 24, there was a M4.3 earthquake at a depth of approximately 5km off-shore east of the Izu Peninsula.":
Approximately 5km southeast of this event, there was light seismic activity during the period from November 10 through 12. Included in this activity, some crustal movements were observed on tiltmeters and strainmeters in the neighboring area.
"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 November 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, November 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 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."
to the text
- On November 3, there was a M3.7 earthquake at a depth of approximately 10km in northern Osaka prefecture (maximum seismic intensity 4). The aftershock activity has mostly subsided.
- Since November 5, there has been a light seismic activity with the largest
event, a M4.8 earthquake off-shore northwest of the Okinawa Main Island.
"On November 15, 2006, at 20:14 (JST) there was a M7.9 earthquake (maximum seismic intensity 2) off-shore east of the Chishima Islands. The focal mechanism showed a reverse fault with a compression axis in a NW-SE direction. It is thought that this event occurred on the plate boundary. According to the GPS data, subtle movements related to this event were observed in northern Hokkaido.":
Associated with this earthquake, tsunamis traveled to the coast of the Okhotsk Sea and the whole Pacific coast (of Japan). The largest tsunami observed in Japan had a height of 84cm (preliminary value at the Tsubota tidal observatory on Miyakejima).
At nearly the same location as the recent event, there was temporarily strong seismic activity with four M6 class earthquakes during the period from late September to early October.
- On December 9, there was a deep M5.9 earthquake at a depth of approximately 440km under the southern Okhotsk Sea.
- On December 13, there was a M3.8 earthquake at a depth of approximately
5km in the Satsuma region, Kagoshima prefecture.
Reference 1Earthquakes 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. |
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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. |