Seismic Activity in Japan November 1999

1 Major Seismic Activity

Earthquakes exceeding magnitude (M)4 and recording seismic intensities of 4 occurred in the Kumamoto region of Kumamoto Prefecture (Pref.), offshore of Fukui Pref., and also in Western Aichi Pref. Otherwise there was no marked activity and all was quiet.

• The whole of Japan M4 (November 1999)

2 Seismic Activity in each Region

(1) Hokkaido Region

* Since July there has been no marked activity.

• Hokkaido Region

(2) Tohoku Region

* An M4.4 earthquake occurred on 7 November in the Hamadori region of Fukushima Pref. at a depth of about 80km.

* An M5.5 earthquake occurred on 15 November offshore of Miyagi Pref. at a depth of about 50km. The focal mechanism was a reverse fault type showing a roughly E-W compressional axis.

• Tohoku Region
• Seismic activity offshore of Miyagi Pref.
• Seismic activity in the Hamadori region of Fukushima Pref.

(3) Kanto-Chubu Region

* An M4.8 earthquake occurred on 7 November offshore of Fukui Pref. at a depth of about 15km. The focal mechanism was a strike-slip type showing a WNW-ESE compressional axis.

* An M4.7 earthquake occurred on 29 November in western Aichi Pref. at a depth of about 50km. The focal mechanism was a strike-slip type showing a roughly E-W tension axis.

* The results of GPS observation in the Tokai (Shizuoka-Aichi-Gifu) area showed no marked variation.

• Kanto-Chubu Region
• Seismic activity in western Aichi Pref. (1)
• Seismic activity in western Aichi Pref. (2)
• Seismic activity offshore of Fukui Pref.
• GPS continuous observation base-line chart (the vicinity of Kakegawa and Omaezaki)
• Base-line-length variation graph
• Height-difference variation graph

(4) Kinki-Chugoku-Shikoku Region

Following the M4.5 earthquake on 30 October in the central Inland Sea area, seismic activity temporarily intensified due to aftershocks. From the latter part of November, however, activity has returned to the level prior to the M4.5 event.

• Kinki-Chugoku-Shikoku Region
• Seismic activity in the central Inland Sea area (offshore of the border between Ehime and Kagawa Prefs.)
• Seismic activity in the central Inland Sea area (offshore of the border between Ehime and Kagawa Prefs.) (M1.6 and greater)

(5) Kyushu-Okinawa Region

* An M6.1 earthquake occurred on 2 November in the vicinity of Taiwan.

* An M4.1 earthquake occurred on 10 November in the Kumamoto region of Kumamoto Pref. at a depth of about 10km. The focal mechanism showed a N-S tension axis. This earthquake, as did the M4.0 event on 31 October, occurred on the northern part of the Hinagu fault.

• Kyushu Region
• Seismic activity in the Kumamoto region of Kumamoto Pref. (in the vicinity of Kamimashiki-gun)
• Okinawa Region
• Seismic activity in the sea near Yonaguni Island

3 Erratum

Herewith we correct an error that occurred in our report on the Tohoku Region in "Seismic Activity in Japan October 1999." Regarding the focal mechanism of the M5.6 earthquake on 3 October offshore of Iwate Prefecture, the direction of the tension axis given as "ENE-WSW", should read "WNW-ESE".