Seismography is the measurement of seismic waves of energy (like vibrations) that travel through the earth’s layers, most commonly associated with earthquakes. Indeed a seismometer’s main function is the monitoring and measuring earthquakes both big and small and such measurements can be a vital help when predicting, for example, the chance of a volcanic eruption or measuring the size and scale of an earthquake. Most of the these earthquakes will originate in tectonic plate movement but some, such as earthquakes caused by fracking for shale gas, are man-made.
Perhaps it is not surprising to discover that the explosion of a nuclear bomb will also result in earthquakes at magnitudes of up to 5.0 on the Richter Scale. Against the backdrop of the catastrophic explosion itself and the radioactive poisoning that such an explosion would bring with it, it might seem at first glance to be less important that an atomic bomb also causes earthquakes. However, it is this secondary effect of the explosion that can help scientists detect and prove that nuclear testing, such as the recent explosions in North Korea, is taking place. Certain types of seismic waves that can only be caused by such an explosion can now be detected by seismologists from a long way away and scientists can now prove where and why the earthquake originated. Such concrete evidence is essential in the highly strained and sensitive political arena where countries have gone to war in the past over even the possibility of a nuclear threat (as we know only too well, and to our cost, from our experience in the Second Gulf War). It is another good example of how the research and success in one field of studies (in this case seismography) can help support the findings of another: How to spot a nuclear bomb