How can the International Monitoring System differentiate between a man-made event and a natural event?

Let us take the example of the difference between naturally occurring earthquakes and man-made explosions. How do seismologists tell the difference? There are some key clues. Most earthquakes are straightforward “shear dislocations”, which means that geological stress causes the rock to fracture along its plane of weakness. The quake generates “P” and “S” waves on certain planes in a recognizable four-lobed pattern. The timeframe depends upon the strength of the quake but usually takes several seconds to propagate over the entire fault plane. 

With man-made explosions, nuclear or otherwise, the dynamics are different. “P” waves extend radially outward, generating equal force in all directions. In principle, there are no initial “S” waves. Energy release in an explosion occurs within a fraction of a second—far faster than in an earthquake. For more information on how the IMS seismic technology works, please click here … 

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