An earthquake is the shaking that results from movement of rock beneath Earth's surface. Earthquakes are measured using a seismograph, with magnitude measured on the Mercalli, Richter, and moment magnitude scales. Major earthquakes can cause landslides, building damage, cracks in the ground, tsunamis, and release of nuclear radiation. Seismic waves called P waves and S waves travel through Earth as both body waves and surface waves. The 2011 Tohoku earthquake in Japan was a magnitude 9.0 quake that caused nuclear problems, evacuation of homes near power plants, and cost millions in damage.