February 12, 2019
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On January 3, there was a magnitude (M) 5.1 earthquake in the Kumamoto region, Kumamoto prefecture. The maximum seismic intensity 6 Lower was observed in the Kumamoto region. Damage with injured persons and so on was caused. In the vicinity of the recent event, there was an M4.3 earthquake occurring on January 26 with maximum seismic intensity 5 Lower observed in the Kumamoto prefecture.
There was no remarkable activity.
* On January 6, there was an M4.5 earthquake at a depth of approximately 100 km under the northern Miyagi prefecture. The focal mechanism had a tension axis in the subducting direction of the plate. This event occurred within the Pacific plate.
* On January 26, there was an M5.6 earthquake at a depth of approximately 40 km, offshore Iwate 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 continental plates.
* On January 14, there was an M4.9 earthquake at a depth of approximately 55 km in 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 January 18, there was an M5.3 earthquake at a depth of approximately 55 km in the southern Ibaraki prefecture [the northeastern Chiba 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 Philippine Sea plates.
There was no remarkable activity
* Refer to the other article (Evaluation of the Earthquake in the Kumamoto region, Kumamoto prefecture on January 3, 2019) for the earthquakes in the Kumamoto region, Kumamoto prefecture on January 3 and 26.
* On January 8, there was an M4.0 earthquake at a depth of approximately 10 km in the ocean area near Amami Oshima. This event occurred within the crust of the continental plate.
* On January 8, there was an M6.0 earthquake at a depth of approximately 30 km in the ocean area near Tanegashima Island. 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. The result of the GNSS observation showed the crustal movement in Tanegashima Island accompanying the event: about 2 cm displacement in south-east direction at Nishinoomote observatory.
* 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.
Note: [ ] is the regional name of the epicenter used in the Japan Meteorological
Agency announcement.
GNSS is a general name of satellite positioning system such as GPS.
February 12, 2019
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude (M) that occurred in Japan and the surrounding area during January 2019.
(reference)
The following events for the period from January 2018 to late December 2018 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities."
| – Near Iriomotejima Island | M5.6 on March 1, 2018 (Depth of approximately 15 km) |
|
| – Western Shimane Prefecture | M6.1 on April 9, 2018 (Depth of approximately 10 km) |
|
| – Offshore southeast of Nemuro Prninsula | M5.4 on April 14, 2018 (Depth of approximately 55 km) |
|
| – Northern Nagano Prefecture | M5.2 on May 12, 2018 (Depth of approximately 10 km) |
|
| – Northern Nagano Prefecture | M5.2 on May 25, 2018 (Depth of approximately 5km) |
|
| – Southern Gunma Prefecture | M4.6 on June 17, 2018 (Depth of approximately 15 km) |
|
| – Northern Osaka Prefecture | M6.1 on June 18, 2018 (Depth of approximately 15 km) |
|
| – Offshore East of Chiba Prefecture | M6.0 on July 7, 2018 (Depth of approximately 55 km) |
|
| – Middle and Eastern Iburi Regions * | M6.7 on September 6, 2018 (Depth of approximately 35 km) |
|
| – Middle and Eastern Iburi Regions * | M5.2 on October 5, 2018 (Depth of approximately 30 km) |
|
| * Seismic activity of the 2018 Hokkaido Eastern Iburi Earthquake | ||
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.
– According to the GNSS observation, a crustal deformation different from the so far trend has been observed in the northern Kyushu since about spring of 2018, and also in the western Shikoku since about autumn of 2018. These phenomena are considered to be caused by a long-term slow slip at the deep part of the boundary between the Philippine Sea and the continental plates in the neighborhood of the northern Hyuganada and Bungo channel.
–"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 February 7 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, February 7, 2019)
"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: