July 10, 2018
Earthquake Research Committee,
Headquarters for Earthquake Research Promotion
* On June 17, there was a magnitude (M) 4.6 earthquake in the southern Gunma prefecture. Maximum seismic intensity 5 Lower was observed in Gunma prefecture and was caused damage with partially destroyed houses and so on.
* On June 18, there was an M6.1 earthquake in the northern Osaka prefecture. Maximum seismic intensity 6 Lower was observed in Osaka prefecture and was caused damage with fatalities and so on.
There was no remarkable activity.
There was no remarkable activity.
* Beginning on June 3, there has been a high seismic activity in the area extending from offshore east of Chiba prefecture to the northeastern and the southern Chiba prefecture: there occurred an M4.9 earthquake on June 12, an M4.4 on June 16, and an M4.3 on June 26. The focal mechanisms of these events showed a reverse fault type with a compression axis roughly in an NNW-SSE direction. All these events occurred at the boundary between the Philippine Sea and the continental plates.
* On June 17, there was an M4.6 earthquake at a depth of approximately 15 km in the southern Gunma prefecture. The focal mechanism showed a reverse fault type with a compression axis in an E-W direction. This event occurred within the crust.
* On June 26, there was an M5.0 earthquake at a depth of approximately 10 km in the northern Hiroshima prefecture. The focal mechanism showed a strike-slip fault type with a compression axis in an E-W direction. This event occurred within the crust.
* On June 12, there was an M5.6 earthquake at a depth of approximately 30 km, offshore east of Osumi peninsula. 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 Philippine Sea and the continental plates.
* 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 July 2 at 02:27 (JST), there was an M4.9 earthquake at a depth of approximately 65 km, offshore east of Aomori 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 July 2 at 20:53 (JST), there was an M5.0 earthquake at a depth of approximately 40 km, offshore east of Aomori 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 July 7, there was an M6.0 earthquake at a depth of approximately 65 km, offshore east of Chiba prefecture. Maximum seismic intensity 5 Lower was observed in Chiba prefecture. The focal mechanism showed a strike-slip fault type with a compression axis in a WNW-ESE direction (preliminary).
July 10, 2018
Earthquake Research Committee
The following are the numbers of earthquakes by magnitude (M) that occurred in Japan and the surrounding area during June 2018.
(reference)
The following events for the period from June 2017 to late May 2018 have been listed as "Major Seismic Activities" in monthly "Evaluation of Seismic Activities."
– Bungo Channel | M5.0 on June 20, 2017 (Depth of approximately 40 km) |
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– Southern Nagano Prefecture | M5.6 on June 25, 2017 (Depth of approximately 5 km) |
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– Central and Eastern Iburi Region | M5.1 on July 1, 2017 (Depth of approximately 25 km) |
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– Aso Region, Kumamoto Prefecture | M4.5 on July 2, 2017 (Depth of approximately 10 km) |
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– Kagoshima Bay | M5.3 on July 11, 2017 (Depth of approximately 10 km) |
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– Southern Inland, Akita Prefecture | M5.2 on September 8, 2017 (Depth of approximately 10 km) |
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– Offshore Fukushima Prefecture | M5.9 on October 6, 2017 (Depth of approximately 55 km) |
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– Near Iriomotejima | M5.6 on March 1, 2018 (Depth of approximately 15 km) |
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– Western Shimane Prefecture | M6.1 on April 9, 2018 (Depth of approximately 10 km) |
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– Offshore southeast of Nemuro Prninsula | M5.4 on April 14, 2018 (Depth of approximately 55 km) |
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– Northern Nagano Prefecture | M5.2 on May 12, 2018 (Depth of approximately 10 km) |
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– Northern Nagano Prefecture | M5.2 on May 12, 2018 (Depth of approximately 10 km) |
There is no supplementary information for Hokkaido region.
There is no supplementary information for Tohoku region.
– "Beginning on June 3, there has been a high seismic activity in the area extending from offshore east of Chiba prefecture to the northeastern and the southern Chiba prefecture: there occurred an M4.9 earthquake on June 12, an M4.4 on June 16, and an M4.3 on June 26. (Excerpted)":
Although the seismic activity is decaying, it still continues: until June
30 there have occurred 8 earthquakes with maximum seismic intensity 3 or
over, and 26 earthquakes with maximum seismic intensity 1 or over. Also
according to the tilt, GNSS and strain data, a slight crustal deformation
was observed in Boso peninsula in early June, and now it has decayed. These
phenomena are considered to be caused by a short-term slow-slip at the
boundary between the Philippine Sea and the continental plates. In this
neighborhood the similar phenomena have been observed once for several
years. In the 2011 case, the maximum magnitude earthquake (M5.2, maximum
seismic intensity 4) occurred more than 1 month after the beginning of
the phenomena.
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 July 6 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, July 6, 2018)
"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: