Now you can’t hide a nuclear explosion in your country. Scientists around the globe continuously monitor seismic wave and these wave patterns tells whether it’s an earth quake, nuclear explosion, blasts from mine field or simply a lorry rolling over a highway and even nuclear explosion under water or inside mountains can be detected easily.
What is seismic wave?
‘Seismo’ is a prefix which means earth quake and seismology is a branch of science deals earthquake. So seismologist is an expert who knows about earthquakes much more than us. They study rocks, tectonic plates, earth crusts and waves. Yes also about waves, different kinds of waves are generated during earthquakes.
Seismologists use special equipment called seismograph (also called seismometer) which can detect and measure these waves. In fact earthquake is a very common phenomenon but we don’t notice all because of low intensity. Don’t forget seismograph can.
Body wave and surface waves are two main types of seismic waves. Body wave can propagate through earth’s inner parts but surface waves can’t. Surface wave is like ripples on water and move along surface only. P waves & S waves are two types of body waves and Love wave & Rayleigh waves are two types of surface waves. It’s a complex phenomenon but one thing you should know that each waves have different speeds and some characteristics e.g. S wave can propagate only through solid rock.
Each and every time scientists knew about North Korean nuclear test before official statements
Yes every time North Korean government proudly declared that they have conducted a nuclear test, but it was not possible to hide even if they wanted to. A cold war era technology is helping scientists around the world.
Cold war era advancement
During the cold war United States were very keen to know about Soviet Union’s (USSR) advancement in nuclear weaponry. So US government funded a research program to monitor seismic waves which is radiated from nuclear test.
No there is a network of seismometers around the world continuously monitoring seismic waves. Seismometer is like a microphone that can detect seismic wave propagates through rocks. This network of seismometers can detect, sea waves on beaches, earthquakes and explosion, because each wave has a very distinct pattern.
How October 2016 test by North Korea was detected
There was no infrasound in atmosphere, underwater sensors were also silent. That means explosion was not in air, under water but covered by rock because seismometers detected something like nuclear explosion and after triangulating the direction scientists were pretty sure that it was a nuclear test in North Korean mountain region. After two weeks of the unusual explosion scientists detected increment of Xenon 133 radionuclide in Yellowknife, Canada which is downwind of North Korea (It’s not possible to completely block radioactive isotopes escaping from test tunnels). After analyzing the wave scientists confirmed that it was like 20 kilotons of TNT.
This network of seismometers is now helping to monitor whether other countries are complying with the Comprehensive Nuclear-Test-Ban Treaty.