This morning, an 8.9 magnitude earthquake occured 230 miles northeast of Tokyo, Japan, causing a large tsunami. The full extent of the impact of the tsunami is not yet known, and there are tsunami alerts for Russia, Hawaii, and the West Coast of the United States. On today's Please Explain, we'll try to answer all of your questions about tsunamis with Humboldt University Professor of Geology Lori Dengler who is currently at the National Weather Service monitoring the situation, and Geoff Abers, a seismologist at the Lamont Doherty Center at Columbia University.