#BREAKING Tsunami warning issued after 6.8 magnitude quake hits Okinawa: NHK
— Agence France-Presse (@AFP) April 20, 2015
JAPAN — A Tsunami warning has been issued after a 6.8 magnitude earthquake hits Okinawa.
National broadcaster NHK said waves were possible on several islands in the southern chain after a very shallow quake centred on Yonaguni in the southwest, near Taiwan.
Witnesses said buildings swayed in Taipei but there was no visible damage in the Taiwan capital.
The quake’s epicenter was 83 kilometers (52 miles) east-northeast of Miyako, Japan, USGS said.
We’re keeping an eye on this story.
Seismotectonics of the Philippine Sea and Vicinity
The Philippine Sea plate is bordered by the larger Pacific and Eurasia plates and the smaller Sunda plate. The Philippine Sea plate is unusual in that its borders are nearly all zones of plate convergence. The Pacific plate is subducted into the mantle, south of Japan, beneath the Izu-Bonin and Mariana island arcs, which extend more than 3,000 km along the eastern margin of the Philippine Sea plate. This subduction zone is characterized by rapid plate convergence and high-level seismicity extending to depths of over 600 km. In spite of this extensive zone of plate convergence, the plate interface has been associated with few great (M>8.0) ‘megathrust’ earthquakes. This low seismic energy release is thought to result from weak coupling along the plate interface (Scholz and Campos, 1995). These convergent plate margins are also associated with unusual zones of back-arc extension (along with resulting seismic activity) that decouple the volcanic island arcs from the remainder of the Philippine Sea Plate (Karig et al., 1978; Klaus et al., 1992).
