June 11, 2013
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On May 18, there was a magnitude (M) 6.0 earthquake offshore Fukushima prefecture. This event had a maximum seismic intensity 5 Upper in Miyagi prefecture.
There was no remarkable activity.
* On May 16, there was a M5.0 earthquake at a depth of approximately 10 km, offshore Iwate prefecture. The focal mechanism showed a normal fault with a tension axis in an N-S direction. This event occurred within the crust of the continental plate.
* On May 18, there was a M6.0 earthquake at a depth of approximately 45 km, offshore Fukushima prefecture. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction. This event occurred on the boundary between the Pacific and the continental plates.
* On May 2, there was a M4.1 earthquake at a depth of approximately 5 km in southern Gunma prefecture. The focal mechanism showed a reverse fault with a compression axis in an NW-SE direction. This event occurred within the crust. In the vicinity of this event, there was a M4.2 earthquake at a depth of approximately 5 km on April 30.
* On May 21, there was a M4.7 earthquake at a depth of approximately 5
km in northern Gunma prefecture [northern Tochigi prefecture]. The focal
mechanism showed a strike-slip fault with a compression axis in an NNW-SSE
direction. This event occurred within the crust.
In the vicinity of the prefectural border of Fukushima, Tochigi and Gunma prefectures, after the 2011 off the Pacific Coast of Tohoku Earthquake, the seismicity has been active, and there was a M6.3 earthquake on February 25. The recent event occurred in its area.
* In the GNSS data for the Tokai region, there have been no changes of activity which are likely to be associated with the Tokai earthquake.
There was no remarkable activity.
There was no remarkable activity.
* On May 14, there was a M7.3 earthquake at a depth of approximately 620 km under the Mariana Islands. The focal mechanism had a compression axis in a dip direction of the Pacific plate. This event occurred within the Pacific plate.
* On May 24 at 14:44, there was a M8.3 earthquake under the Sea of Okhotsk [under the ocean near Sakhalin] (M: Japan Meteorological Agency, the other hypocentral parameter: USGS). The focal mechanism had a compression axis in a dip direction of the Pacific plate. This event occurred within the Pacific plate. In addition, under the Sea of Okhotsk there was a M6.7 earthquake at 23:56 on same day.
* On June 2, there was a M6.3 earthquake near Taiwan (central Taiwan). The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction. In the vicinity of this event, there was a M6.1 earthquake on March 27.
* On June 4, there was a M4.7 earthquake at a depth of approximately 50 km, offshore Fukushima prefecture. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction. This event occurred on the boundary between the Pacific and the continental plates.
* On June 6, there was a M5.0 earthquake at a depth of approximately 50 km, offshore east of Chiba prefecture. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction. This event occurred on the boundary between the Pacific and the Philippine Sea plates.
* On June 7, there was a M3.8 earthquake at a depth of approximately 10 km, offshore Jo-Chuetsu, Niigata prefecture [Joetsu region, Niigata prefecture]. The focal mechanism showed a reverse fault with a compression axis in an E-W direction. This event occurred within the crust.
* On June 8, there was a M5.8 earthquake at a depth of approximately 25 km under the ocean near Yonagunijima. The focal mechanism had a compression axis in an NNW-SSE direction (preliminary).
* On June 8 at 16:17, there was a M4.0 earthquake at a depth of approximately 5 km in northern Wakayama prefecture. The focal mechanism showed a reverse fault with a compression axis in a WNW-ESE direction (preliminary). This event occurred within the crust. In the vicinity of this event, the seismicity, to some extent, such as a M3.9 earthquake on same day at 20:39 was seen.
Note: [ ] was the regional name of the epicenter used in the Japan Meteorological
Agency announcement.
GNSS (Global Navigation Satellite System)
is a general name of satellite positioning system such as GPS.
June 11, 2013
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during May 2013.
(reference)
The following events for the period from May 2012 to late April 2013 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities"
| – Offshore East of Aomori Prefecture | M6.1 on May 24, 2012 (Depth of approximately 60 km) |
|
| – Northern Nagano Prefecture | M5.2 on July 10, 2012 (Depth of approximately 10 km) |
|
| – Southern Tokachi Region | M6.1 on August 25, 2012 (Depth of approximately 50 km) |
|
| – Offshore Miyagi Prefecture | M5.6 on August 30, 2012 (Depth of approximately 60 km) |
|
| – Offshore Miyagi Prefecture | M5.6 on October 25, 2012 (Depth of approximately 50 km) |
|
| – Offshore Sanriku | M7.3 on December 7, 2012 | |
| – Northern Ibaraki Prefecture | M4.8 on January 28, 2013 (Depth of approximately 75km) |
|
| – Northern Ibaraki Prefecture | M4.7 on January 31, 2013 (Depth of approximately 10km) |
|
| – Southern Tokachi Region | M6.5 on February 2, 2013 (Depth of approximately 100 km) |
|
| – Northern Tochigi Prefecture | M6.3 on February 25, 2013 (Depth of approximately 5 km) |
|
| – Near Awajishima | M6.3 on April 13, 2013 (Depth of approximately 15 km) |
|
| – Under the Ocean Near Miyakejima | M6.2 on April 17, 2013 (Depth of approximately 10 km) |
|
| – Offshore Miyagi Prefecture | M5.9 on April 17, 2013 (Depth of approximately 60 km) |
There is no supplementary information for the Hokkaido region.
There is no supplementary information for Tohoku region.
– During about one year after March 2012, the number of earthquakes
of M4.0 or over in the aftershock area of the 2011 off the Pacific Coast
of Tohoku Earthquake became under one fifth smaller than the one during
about one year just after the 2011 off the Pacific Coast of Tohoku Earthquake,
and thus the aftershock activity has been decaying. However, in comparison
with the mean activity before the 2011 off the Pacific Coast of Tohoku
Earthquake, the number of earthquakes of M4.0 or over in the aftershock
area was more than five times, and the aftershock activity still remains
in brisk state.
According to the GNSS data during about one month just after the 2011 off the Pacific Coast of Tohoku Earthquake, at the maximum value, the horizontal movement was 30 cm, and the vertical subsidence and upheaval were 6 cm and 5 cm respectively. The movement was gradually decaying. Although the horizontal movement was slightly larger than 1 cm, and the vertical movement was less than 1cm during the recent one month, crustal movements which are thought to be the postseismic deformation have still been observed in a wide area from the Tohoku through the Kanto-Chubu regions.
In case of the earthquake (moment magnitude (Mw) 9.1) offshore west of the northern Sumatra Island in December 2004, within the source area and its surroundings, there have been large earthquakes for long period. As to the 2011 off the Pacific Coast of Tohoku Earthquake, within the aftershock area and its surroundings, there is fear that large earthquakes will occur from now on, and there is a possibility that it will be hit by strong shaking and high tsunami. It is necessary to do care continuously for it.
–"In the GNSS data for the Tokai region, there have been no changes
of activity which are likely to be associated with the Tokai earthquake":
(This evaluation is in agreement with the views presented at the regular meeting on May 28 of the Assessment Committee for Areas under Intensified Measures against Earthquake Disaster (reference below).)
(Reference)
Recent seismic and crustal activity in the Tokai region and its vicinity (Seismological and Volcanological Department, Japan Meteorological Agency, May 28)
"No changes of activity which are likely to be associated with the Tokai earthquake have been observed until now. (Excerpted))"
There is no supplementary information for Kinki-Chugoku-Shikoku region.
There is no supplementary information for Kyushu-Okinawa region.
There is no supplementary information for Other 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: