1968 Hyūga-nada earthquake
|Date||April 1, 1968|
The 1968 Hyūga-nada earthquake (Japanese: 1968年日向灘地震) occurred on April 1, 1968 at 09:42 local time (00:42 UTC). The earthquake had a magnitude of Mw 7.5, and the epicenter was located in Hyūga-nada Sea, off the islands of Kyushu and Shikoku, Japan. The magnitude of this earthquake was also given as Mjma 7.5. A tsunami was observed. There were 15 people reported injured. The intensity reached shindo 5 in Miyazaki and Kōchi.
This earthquake was an interplate earthquake between the Eurasian Plate and the Philippine Sea Plate. In this region, the Philippin Sea Plate is subducting beneath the Eurasian Plate. The subduction interface around this region include the Nankai Trough and the Ryukyu Trench.
This earthquake is the strongest event recorded in the Hyūga-nada Sea region. The maximum slip was estimated to be 4 m. It was estimated that, in the Hyūga-nada Sea region, earthquakes with magnitudes about 7.6 occur with a period of about 200 years, while earthquakes with magnitudes about 7.1 occur with a period of about 20 to 27 years. It has been pointed out that there is a tendency of occurrence of inland earthquakes in Kyushu before and after large interplate earthquakes in the Hyūga-nada Sea region.