September 9, 2016
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On August 31, there was a magnitude (M) 5.2 earthquake in Kumamoto region, Kumamoto prefecture. This event had a maximum seismic intensity 5 Lower observed in Kumamoto prefecture and caused damage with injured persons and so on.
There was no remarkable activity.
* On August 15, there was a M5.6 earthquake offshore Fukushima prefecture. The focal mechanism had a compression axis in an E-W direction.
* On August 20, there was a M6.4 earthquake at a depth of approximately 10 km (CMT solution), offshore Sanriku. In addition, on August 21, there was a M6.2 earthquake at almost the same place. The focal mechanisms showed a reverse fault type with a compression axis in a WNW-ESE direction. These events occurred on the boundary between the Pacific and the continental plates. Including these events, there were 7 earthquakes of M5.0 or over in 3 days from August 20 to 22 offshore Sanriku.
* On August 22, there was a M5.3 earthquake at a depth of approximately 35 km, offshore Miyagi prefecture. The focal mechanism showed a normal fault type with a tension axis in an N-S direction.
* On August 5, there was a M6.4 earthquake at a depth of approximately 530 km under the ocean area near Iwotou Island. The focal mechanism had a compression axis in the subducting direction of the Pacific plate. This event occurred within the Pacific plate.
* On August 19, there was a M5.4 earthquake at a depth of approximately 50 km offshore Ibaraki prefecture. The focal mechanism of this event had a compression axis in an NNW-SSE direction.
* On August 26, there was a M6.1 earthquake at a depth of approximately 500 km under the ocean area near Torishima. The focal mechanism had a compression axis in the subducting direction of the Pacific plate. This event occurred within the Pacific plate.
* In the GNSS data for the Tokai region, there has been no change of activity which is likely to be associated with the Tokai earthquake.
There was no remarkable activity.
* A series of seismic activity of the 2016 Kumamoto Earthquakes, in the area extending from Kumamoto region, Kumamoto prefecture to the central Oita prefecture, including a M6.5 earthquake on April 14 and a M7.3 one on April 16, is continually decaying as a whole. The activity in the Kumamoto region and the Aso region is still continuing in August: On August 31, there was a M5.2 earthquake (maximum seismic intensity 5 Lower) in the Kumamoto region. In addition, there were 2 earthquakes (1 in July) with maximum seismic intensity 4 and 3 earthquakes (8 in July) with maximum seismic intensity 3. The activity in the central Oita prefecture has decayed. According to the GNSS observation, crustal deformation is still observed in the area centered on the series of the seismic activity.
Note:GNSS (Global Navigation Satellite System) is a general name of satellite positioning system such as GPS.
September 9, 2016
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during August 2016.
(reference)
The following events for the period from August 2015 to late July 2016 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities."
| – Tokyo Bay | M5.2 on September 12, 2015 (Depth of approximately 55 km) |
|
| – Central Coast of Chile | Mw8.3 on September 17, 2015 | |
| – Offshore West of the Satsuma Peninsula | M7.1 on November 14, 2015 | |
| – Sanpachi-Kamikita Region, Aomori Prefecture | M4.6 on January 11, 2016 (Depth of approximately 10 km) |
|
| – Offshore Urakawa | M6.7 on January 14, 2016 (Depth of approximately 50 km) |
|
| – Kumamoto Earthquakes | M6.5 on April 14, 2016 and M7.3 on April 16, 2016 (Depth of approximately 10 km) |
|
| – Southern Ibaraki Prefecture | M5.5 on May 16, 2016 (Depth of approximately 40 km) |
|
| – Uchiura Bay | M5.3 on June 16, 2016 (Depth of approximately 10 km) |
|
| – Northern Ibaraki Prefecture | M5.4 on July 27, 2016 (Depth of approximately 55 km) |
There is no supplementary information for Hokkaido region.
There is no supplementary information for Tohoku region.
–"In the GNSS data for the Tokai region, there has been no change
of activity which is likely to be associated with the Tokai earthquake.":
(This evaluation is in agreement with the views presented at the regular
meeting on August 29 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, August 29, 2016)
"No change of activity which is likely to be associated with the Tokai earthquake has been observed until now. (Excerpted)"
– Non-stationary crustal deformation surrounding the Kii Channel observed from mid-2014 is now decaying. This deformation is thought to be due to a slow slip (slow-slip) at the boundary between the Philippine Sea and the continental plates.
– Non-stationary crustal deformation surrounding the Bungo Channel observed from around December 2015 is still continuing. This deformation is thought to be due to a slow slip (slow-slip) at the boundary between the Philippine Sea and the continental plates.
There is no supplementary information for 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: