Gregory Jaczko and others testified on U.S. efforts to assist the Japanese following a series of nuclear accidents at the Fukushima power plant caused by failures related to a devastating earthquake and tsunami. In his testimony Gregory Jaczko gave a bleaker assessment of the threat than one given by the Japanese government, saying Japanese emergency workers at one plant could face lethal levels of radiation, while advising Americans to evacuate a wider area. They also talked about U.S. nuclear power plant safety and their ability to withstand earthquakes and other natural disasters.