8 September 1999
Headquarters for Earthquake Research Promotion
Earthquake Research Committee

Seismic Activity in Japan August 1999


1 Major Seismic Activity

* Except for a Magnitude (M) 5.4 earthquake that occurred on 21 August in northern Wakayama Prefecture (Pref.), there was no marked activity; all was quiet.

2 Seismic Activity in each Region


(1) Hokkaido Region

* As was the case in July, there was no marked activity.

(2) Tohoku Region

* Since June there has been no marked activity.

(3) Kanto-Chubu Region

* An M4.0 earthquake occurred on 11 August in Tokyo Bay at a depth of about 60km.

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

(4) Kinki-Chugoku-Shikoku Region

* An M5.4 earthquake occurred on 21 August in northern Wakayama Pref. at a depth of about 70km, and a maximum intensity of 5 lower was recorded. The hypocenter was inside the subducting Philippine Sea Plate. Only several aftershocks were recorded.

(5) Kyushu-Okinawa Region

* There was no marked activity this month.