July 11, 2016
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On June 16, there was a magnitude (M) 5.3 earthquake in Uchiura Bay. This event had a maximum seismic intensity 6 Lower observed in Hokkaido and caused damage with injured persons and so on.
* On June 16, there was a M5.3 earthquake at a depth of approximately 10 km in Uchiura Bay. The focal mechanism showed a reverse fault type with a compression axis in an NE-SW direction. This event occurred within the crust of the continental plate. There was a high seismic activity before the M5.3 earthquake and 39 earthquakes with seismic intensity 1 or over occurred until July 4, including a M4.2 one on June 21 and so on.
* On June 27, there was a M5.9 earthquake offshore Fukushima prefecture. The focal mechanism showed a reverse fault type with a compression axis in a WNW-ESE direction.
* On June 12, there was a M4.8 earthquake at a depth of approximately 40 km under the southern Ibaraki prefecture. The focal mechanism of this event showed a reverse fault type with a compression axis in an NNW-SSE direction. This event occurred at the boundary between the Philippine Sea and the continental plates.
* There was a high seismic activity in the Joetsu region, Niigata prefecture (near the boundary between Niigata and Nagano prefectures), beginning on June 25. 13 earthquakes with seismic intensity 1 or over occurred until July 1. This seismic activity occurred within the crust. The maximum is the M4.8 earthquake, occurring at a very shallow depth on June 25, the focal mechanism of which showed a strike-slip fault type with a compression axis in a WNW-ESE direction. On July 1, there was a M4.6 earthquake.
* 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 addition to a M4.3 earthquake (maximum seismic intensity 5 Lower) on June 12, there were 4 earthquakes with maximum seismic intensity 4 and 14 earthquakes with maximum seismic intensity 3 in June (8 and 43 in May, respectively). There has been no earthquake of M5.0 or over and earthquake with seismic intensity 5 Upper since April 19. The activity in the central Oita prefecture has decayed in May: there were 3 earthquakes with maximum seismic intensity 1 in June (1 earthquake with maximum seismic intensity 2 and 5 earthquakes with maximum seismic intensity 1 in May). According to the GNSS observation, crustal deformation was observed in the area centered on the series of the seismic activity.
* On June 24, there was a M6.2 earthquake in the ocean area near Yonagunijima. The focal mechanism of this event showed a strike-slip fault with a tension axis in an N-S direction.
Note:GNSS (Global Navigation Satellite System) is a general name of satellite positioning system such as GPS.
July 11, 2016
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude that occurred in Japan and the surrounding area during June 2016.
(reference)
The following events for the period from June 2015 to late May 2016 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities."
| – Abashiri Region | M5.0 on June 4, 2015 (At a very shallow depth) |
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| – Northern Inland of Iwate Prefecture | M5.7 on July 10, 2015 (Depth of approximately 90 km) |
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| – Southern Oita Prefecture | M5.7 on July 13, 2015 (Depth of approximately 60 km) |
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| – Tokyo Bay | M5.2 on September 12, 2015 (Depth of approximately 55 km) |
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| – 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) |
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| – Offshore Urakawa | M6.7 on January 14, 2016 (Depth of approximately 50 km) |
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| – Kumamoto Earthquakes | M6.5 on April 14, 2016 and M7.3 on April 16, 2016 (Depth of approximately 10 km) |
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| – Southern Ibaraki Prefecture | M5.5 on May 16, 2016 (Depth of approximately 40 km) |
– "On June 16, there was a M5.3 earthquake at a depth of approximately
10 km in Uchiura Bay. (Excerpted) ":
In the southern Oshima peninsula where the recent seismic activity is observed,
clusters of earthquakes with magnitudes of the same order occur, such as
the cluster offshore Hakodate from 1978 to 1982 and the cluster offshore
Matsumae from 1995 to 1997.
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 June 27 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, June 27, 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.
–"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, (Excerpted).":
Judging from the decaying situation of seismic activity to the present,
in the Kumamoto region, Kumamoto prefecture and Aso region, the present
aftershock activity will continue for a while, but we conclude that the
possibility of occurrence of a M5 or so aftershock (maximum seismic intensity
of order of 5 Upper) has been lowered.
– There was a seismic activity in the ocean area near Tokara Islands, beginning on July 4, and there were 18 earthquakes with maximum seismic intensity 1 or over, until July 10.
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: