January 15, 2018
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
There was no remarkable activity.
There was no remarkable activity.
* On December 16, there was a magnitude (M) 5.5 earthquake at a depth of approximately 50 km, offshore Iwate prefecture. The focal mechanism showed a strike-slip fault type with a compression axis in an ENE-WSW direction. This event occurred within the Pacific plate.
* On December 2, there was an M4.4 earthquake at a depth of approximately 45 km under the southern Ibaraki prefecture. The focal mechanism showed a reverse fault type with a compression axis in an NW-SE direction. This event occurred at the boundary between the Philippine Sea and the continental plates.
* On December 6, there was an M5.3 earthquake at a depth of approximately 10 km in the middle Nagano prefecture. The focal mechanism showed a strike-slip fault type with a compression axis in a WNW-ESE direction. This event occurred within the crust.
* On December 6, there was an M4.5 earthquake at a depth of approximately 10 km in the northern Ibaraki prefecture. The focal mechanism showed a normal fault type with a tension axis in an NE-SW direction. This event occurred within the crust.
* On December 21, there was an M6.0 earthquake at a depth of approximately 10 km (CMT solution) in the ocean area near Torishima. The focal mechanism showed a reverse fault type with a compression axis in an E-W direction.
* On December 27, there was an M4.5 earthquake at a depth of approximately 70 km under the Tokyo Bay [the northwestern Chiba prefecture]. The focal mechanism showed a reverse fault type with a compression axis in an E-W direction. This event occurred at the boundary between the Pacific and the Philippine Sea plates.
There was no remarkable activity.
There was no remarkable activity.
There has been observed no unusual change which indicates that the possibility of occurrence of great earthquakes along the Nankai Trough has relatively raised compared to the normal time.
* On January 6, there was an M4.7 earthquake at a depth of approximately 70 km under the Tokyo Bay [the northwestern Chiba prefecture]. The focal mechanism showed a reverse fault type with a compression axis in an E-W direction. This event occurred at the boundary between the Pacific and the Philippine Sea plates.
* On January 6, there was an M4.5 earthquake at a depth of approximately 10 km, offshore east of Izu peninsula [the ocean area near Izu Oshima]. The focal mechanism showed a strike-slip fault type with a compression axis in an NW-SE direction. This event occurred within the crust of the Philippine Sea plate.
Note: [ ] is the regional name of the epicenter used in the Japan Meteorological
Agency announcement.
January 15, 2018
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude (M) that occurred in Japan and the surrounding area during December 2017.
(reference)
The following events for the period from December 2016 to late November 2017 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities."
| – 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) |
|
| – Southern Inland, Akita Prefecture | M5.2 on September 8, 2017 (Depth of approximately 10 km) |
|
| – Offshore Fukushima Prefecture | M5.9 on October 6, 2017 (Depth of approximately 55 km) |
There is no supplementary information for Hokkaido region.
There is no supplementary information for Tohoku region.
There is no supplementary information for Kanto-Chubu region.
There is no supplementary information for Kinki-Chugoku-Shikoku region.
There is no supplementary information for Kyushu-Okinawa region.
"There has been observed no unusual change which indicates that the
possibility of occurrence of great earthquakes along the Nankai Trough
has relatively raised compared to the normal time.":
(This evaluation is in agreement with the views presented at the regular meeting on December 25 of the Assessment Committee for Earthquakes along the Nankai Trough (reference below).)
(Reference)
Recent crustal activity around the Nankai Trough (Seismological and Volcanological Department, Japan Meteorological Agency, December 25, 2017)
"In the present, there has been observed no unusual change which indicates that the possibility of occurrence of great earthquakes along the Nankai Trough has relatively raised compared to the normal time.(Excerpted)"
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: