Unusual Strong Ground Motion Across Japan From the 680 km Deep 30 May 2015 Ogasawara Islands Earthquake

The Mw 7.9 earthquake beneath the Ogasawara Islands on 2015 May 30 at 680 km depth (about 100 km deeper than other seismicity in the vicinity) produced significant shaking over a broad area of Japan in the epicentral distance range 1,000–2,000 km. Usually, deep earthquakes in the subducting Pacific slab develop a band of large ground motion along the east coast of northern Japan, due to efficient guiding of high-frequency (>1 Hz) waves in the subducting slab. However, for this very deep earthquake, the large ground acceleration arises from relatively low-frequency (<1 Hz) S wave pulses with a long tail of long-period (