Most of the foreshocks are interplate earthquakes with thrust-type focal mechanisms. Both interplate and intraplate earthquakes appeared in the aftershocks offshore Sanriku coast with considerable proportions. Energy The surface energy of the seismic waves from the earthquake was calculated to be joules, which is nearly double that of the 9.1 Mw 2004 Indian Ocean earthquake and tsunami that killed 230,000 people. If harnessed, the seismic energy from this earthquake would power a city the size of Los Angeles for an entire year. The seismic moment (M0), which represents a physical size for the event, was calculated by the USGS at 3.9×1022 joules, slightly less than the 2004 Indian Ocean quake. Japan's National Research Institute for Earth Science and Disaster Prevention (NIED) calculated a peak ground acceleration of 2.99 g (29.33 m/s2). The largest individual recording in Japan was 2.7 g, in Miyagi Prefecture, 75 km from the epicentre; the highest reading in the Tokyo metropolitan area was 0.16 g. Intensity The strong ground motion registered at the maximum of 7 on the Japan Meteorological Agency seismic intensity scale in Kurihara, Miyagi Prefecture. Three other prefectures—Fukushima, Ibaraki and Tochigi—recorded an 6 upper on the JMA scale. Seismic stations in Iwate, Gunma, Saitama and Chiba Prefecture measured a 6 lower, recording an 5 upper in Tokyo. Geophysical effects Portions of northeastern Japan shifted by as much as closer to North America, making some sections of Japan's landmass wider than before. Those areas of Japan closest to the epicenter experienced the largest shifts. A stretch of coastline dropped vertically by , allowing the tsunami to travel farther and faster onto land. One early estimate suggested that the Pacific plate may have moved westward by up to , and another early estimate put the amount of slippage at as much as 40 m (130 ft). On 6 April the Japanese coast guard said that the quake shifted the seabed near the epicenter and elevated the seabed off the coast of Miyagi Prefecture by . A report by the Japan Agency for Marine-Earth Science and Technology, published in Science on 2 December 2011, concluded that the seabed in the area between the epicenter and the Japan Trench moved east-southeast and rose about as a result of the quake. The report also stated that the quake had caused several major landslides on the seabed in the affected area. The Earth's axis shifted by estimates of between