October 11, 2017
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On September 8, there was a magnitude (M) 5.2 earthquake in the southern inland, Akita prefecture. Maximum seismic intensity 5 Upper was observed in Akita prefecture and was caused damage with partially destroyed houses and so on.
* On September 10, there was an M5.6 earthquake at a depth of approximately 45 km, offshore Urakawa. The focal mechanism showed a reverse fault type with a compression axis in a WNW-ESE direction. This event occurred at the boundary between the Pacific and the continental plates.
* On September 8, there was an M5.2 earthquake at a depth of approximately 10 km in the southern inland, Akita prefecture. The focal mechanism showed a strike-slip fault type with a tension axis in an NW-SE direction. This event occurred within the crust.
* On September 20, there was an M5.3 earthquake at a depth of approximately 45 km, offshore Fukushima prefecture. The focal mechanism showed a reverse fault type with a compression axis in a WNW-ESE direction. This event occurred at the boundary between the Pacific and the continental plates.
* On September 21, there was an M6.3 earthquake at a depth of approximately 20 km (CMT solution), offshore Sanriku. The focal mechanism showed a normal fault type with a tension axis in a WNW-ESE direction. This event occurred within the Pacific plate east of the Japan Trench.
* On September 27, there was an M6.1 earthquake at a depth of approximately 35 km, offshore Iwate prefecture. The focal mechanism showed a reverse fault type with a compression axis in a WNW-ESE direction. This event occurred at the boundary between the Pacific and the continental plates.
* On September 8, there was an M6.1 earthquake at a depth of approximately 480 km, offshore west of Ogasawara Islands. The focal mechanism had a compression axis in the subducting direction of the Pacific plate. This event occurred within the Pacific plate.
* On September 14, there was an M4.5 earthquake at a depth of approximately 50 km under the southern Saitama prefecture. The focal mechanism showed a reverse fault type with a compression axis in an NNW-SSE direction. This event occurred within the Philippine Sea plate.
* In the GNSS data for the Tokai region, there has been no unusual change of activity which is likely to be associated with the Tokai earthquake.
There was no remarkable activity.
* On September 8, there was an M4.1 earthquake at a depth of approximately 15 km in the Kumamoto region, Kumamoto prefecture. The focal mechanism showed a normal fault type with a tension axis in an N-S direction. This event occurred within the crust.
* On October 1, there was an M4.9 earthquake at a depth of approximately 5 km in the northern Ibaraki prefecture. The focal mechanism showed a normal fault type with a tension axis in an E-W direction. This event occurred within the crust.
* On October 6, there was an M6.3 earthquake at a depth of approximately 10 km (CMT solution), offshore Fukushima prefecture. The focal mechanism showed a normal fault type with a tension axis in a WNW-ESE direction. This event occurred within the Pacific plate east of the Japan Trench.
* On October 6, there was an M5.9 earthquake at a depth of approximately 55 km, offshore Fukushima prefecture. The focal mechanism showed a reverse fault type with a compression axis in a WNW-ESE direction. This event occurred at the boundary between the Pacific and the continental plates.
Note: GNSS is a general name of satellite positioning system such as GPS.
October 11, 2017
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude (M) that occurred in Japan and the surrounding area during September 2017.
(reference)
The following events for the period from September 2016 to late August 2017 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities."
| – Ocean Area near Okinawa Main Island | M5.6 on September 26 (Depth of approximately 45 km) |
|
| – Central Tottori Prefecture | M6.6 on October 21, 2016 (Depth of approximately 10 km) |
|
| – Offshore Fukushima Prefecture | M7.4 on November 22, 2016 (Depth of approximately 10 km) |
|
| – Northern Ibaraki Prefecture | M6.3 on December 28, 2016 (Depth of approximately 10 km) |
|
| – Offshore Fukushima Prefecture | M5.7 on February 28, 2017 (Depth of approximately 50 km) |
|
| – Bungo Channel | M5.0 on June 20, 2017 (Depth of approximately 40 km) |
|
| – Southern Nagano Prefecture | M5.6 on June 25, 2017 (Depth of approximately 5 km) |
|
| – Central and Eastern Iburi Region | M5.1 on July 1, 2017 (Depth of approximately 25 km) |
|
| – Aso Region, Kumamoto Prefecture | M4.5 on July 2, 2017 (Depth of approximately 10 km) |
|
| – Kagoshima Bay | M5.3 on July 11, 2017 (Depth of approximately 10 km) |
There is no supplementary information for Hokkaido region.
–"On September 8, there was an M5.2 earthquake at a depth of
approximately 10 km in the southern inland, Akita prefecture. (Excerpted.)
":
There is an aftershock activity in the vicinity of this event. 49 earthquakes
with seismic intensity 1 or over occurred until September 30, including
that one with maximum seismic intensity 4 occurring on September 9.
–"In the GNSS data for the Tokai region, there has been no unusual 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 September 25 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, September 25, 2017)
"There has been no unusual change of activity which is likely to be associated with the Tokai earthquake until now. (Excerpted)"
There is no supplementary information for Kinki-Chugoku-Shikoku region.
–"On September 8, there was an M4.1 earthquake at a depth of
approximately 15 km in the Kumamoto region, Kumamoto prefecture. (Excerpted.)
":
In September, 1 earthquake (0 in August) with maximum seismic intensity
4 or over and 1 earthquake (1 in August) with maximum seismic intensity
3 occurred in the Kumamoto and Aso regions, Kumamoto prefecture. A series
of seismic activity of the 2016 Kumamoto Earthquakes in the Kumamoto and
Aso regions still continues, decaying as a whole, and the seismic activity
at present will continue for a while. According to the GNSS observation,
postseismic deformation in the area centered on the series of the seismic
activity is subsiding as a whole.
– The seismic activity in the Kagoshima bay after an M5.3 earthquake on July 11 continues, decaying as a whole.
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: