How to Tell The Difference Between a Nuclear Bomb Test and an Earthquake

[Rogue Valley]

How to Tell The Difference Between a Nuclear Bomb Test and an Earthquake


"Shortly after North Korea claimed it had tested a hydrogen bomb — a weapon potentially hundreds of times more powerful than the fission bombs the country had already set off — seismologists at the United States Geological Survey, or USGS, went to work trying to understand the event. Their early findings suggest that a nuclear bomb test did occur but that it wasn’t a hydrogen bomb. So how do you tell the difference?"

 

[American]

Onset, magnitude and duration of the seismic pulses?

 

[Oozlefinch]

Onset, magnitude and duration of the seismic pulses?

Location for one. Are there any active faults in the area? Is it in the same area as previous tests or earthquakes?

Then you have the waves themselves. Primarily P-waves and S-waves. These are the 2 main waves that cause damage in earthquakes. The P-waves are the first ones to strike, passing through any medium at the speed of sound, causing the initial jolt. Then the S-waves follow, changing form and feature because of what they pass through. These are the ones that typically do the most damage during an earthquake, lasing longer and changing because of terrain. Liquifaction is caused by S-waves, not P-waves. The 30-90 second long rolling of the ground is caused by S-waves, not P-waves.

Then you have duration. Is the event a P-wave followed by S-waves, or is it largely only a P-wave event?

Finally, aftershocks. Are there aftershocks (which you would have after a seismic event), or not?

Having lived most of my life in Earthquake Country, this is the kind of thing I have been looking into for decades. It is really not hard to tell the 2 apart. An explosion looks very different from an Earthquake when looked at by the waves produced. One starts with a strong event then continues for several minutes. The other is a single strong event that ends quickly. In the following hours and days one shows repeated events as the fault(s) is re-establishing itself (aftershocks), the other has no follow-up events.