killed as many as 18000 people. what about the united states? the risk is rising for a california quake as powerful as an 8.9. that is 90 times more energy than this quake that hit north ridge, california in 1994. we are joined by richard from the university of berkely. richard, we look at the chance being greater, experts say the risk used to be 4.7 and now at seven percent. that is the difference. what significance is that? it does make a difference. we know that there is a real risk of significant earthquakes like the north ridge earthquake. but there are three big events that increased in likelihood from 4 to 7 percent. it is a reminder that we have to