How North Korea tests a nuclear weapon for targets

 With an earthquake, it’s the opposite: The primary waves are weaker and the secondary waves and stronger secondary waves.Clues before a test North Korea has one nuclear test site: Punggye-ri. In the long-term lead-up to the test, there’s usually a flurry of activity, some of which is captured by satellite imagery and can offer clues to observers on what’s going on.