Two powerful earthquakes have struck near the southern Japanese city of Kumamoto. Just the day before, a 6.2 magnitude quake resulted in at least 9 fatalities and over 800 injuries. A tsunami warning is in effect.
The earthquakes had a magnitude of 7.1 (4.4 miles) at a depth of 7km and a 7.4 at a depth of 40km (25 miles), according to officials.
According to the USGS, the April 15, 2016 M 7.0 earthquake north of Kumamoto, on the island of Kyushu in southwest Japan, occurred as the result of strike-slip faulting at shallow depth. Focal mechanisms for the earthquake indicate slip occurred on either a left-lateral fault striking to the northwest, or on a right-lateral fault striking northeast. While the earthquake occurred several hundred kilometers northwest of the Ryukyu Trench, where the Philippine Sea plate begins its northwestward subduction beneath Japan and the Eurasia plate, the shallow depth and faulting mechanism of this earthquake indicate it occurred on a crustal fault within the upper Eurasia plate.
In contrast to this recent sequence of shallow earthquakes, most seismicity in the Kyushu region is related to the subduction of the Philippine Sea plate at depth.