The magnitude 7.9 Bonin Islands earthquake sequence in May 2015, which ruptured deep within the earth near the base of the upper mantle, did not include an aftershock that extended to record depths into the lower mantle, according to a study appearing in The Seismic Record. The magnitude 7.9 Bonin Islands earthquake sequence in May 2015, which ruptured deep within the earth near the base of the upper mantle, did not include an aftershock that extended to record depths into the lower mantle, according to a study appearing in The Seismic Record. Earth Sciences Phys.org – latest science and technology news stories