When I was at Caltech I designed this experiment to model a underground Nuclear Blast. Started with a 12" cube of limestone and milled out a 20cm circular cavity right in the middle. Placed High Explosive charge right in the middle of the cavity. Had strain gages on the block and a high speed data logger.
North Korea fired seven ballistic missiles off its eastern coast Saturday, South Korea said, a violation of U.N. resolutions and an apparent message of defiance to the United States on its Independence Day.