september 3rd. north korea s sixth and largest test. they have suggested this may be the real reason kim jong-un agreed to stop nuclear testing. images from digital globe from before and after the september test show that mount man test site of the under ground test may, in fact, have collapsed. the test site is 60 miles from the border with china in the northeast of the country. that test in september which was ten times the size of north korea s previous test occurred 2300 feet under ground, 8 and a half minutes later an earthquake was recorded followed by three more earthquakes. scientists from china believe the mount man test actually collapsed. the head of u.s. pacific command admiral harry harris, has questioned kim jong-un s motive.