we are getting incredible before and after images from japan. take a look at the city of sendai last april. now you can look at the tsunami-ravaged city, photo taken yesterday. just a few homes remaining. the new york times website posted the original images. amazing to see exactly what took place in the city of sendai. the shaking is not over. aftershocks rock parts of japan. more than 150 and counting still. dr. david applegate is a senior adviser for earthquake and geologic hazards at the usgc. good to have you on today. can we determine how long these aftershocks will continue going on for such a massive quake or is it just unknown? what is known is that aftershocks decay what we call