The answer to your question is no, a nuclear explosion can not be simulated by a chemical explosion. Why?

The yield of a nuclear weapon is a measure of explosive energy it carries.  It is the usual practice to state the yield in terms of a quantity of TNT that would generate a comparable amount of energy when it explodes.  Thus, a one-kiloton nuclear weapon is one which produces the same amount of energy in an explosion as does one kiloton, or 1,000 tons, of TNT.  Similarly, a one-megaton weapon would have the energy equivalent of one million tons of TNT.  As a general rule, most fission devices have powers in the range from about I kiloton up to about 22 kilotons, but fusion devices have powers measured in megatons.  A typical fusion device could have IO megatons of power and some can generate 50 megatons or more.  These awesome figures show how science has created a powerful monster in the form of nuclear weapons.

 The effects that a nuclear explosion has on people, buildings, and the environment can vary greatly, depending on a number of factors.  These factors include weather, terrain, the point of explosion in relation to the earth's surface, and the weapon's yield. The weapon's explosion would produce three basic phases: a blast wave, thermal radiation, and residual nuclear radiation.  

The explosion begins with the formation of a 'fireball', which consists of a cloud of dust and of extremely hot gases under very high pressure.  A fraction of a second after the explosion, the gases begin to expand and form a blast wave.  This wave moves rapidly away from the 'fireball' like a moving wall of highly compressed air.  As the wave moves forward, it creates overpressure, which is an atmospheric pressure above the normal level.  A one-megaton explosion can produce enough overpressure to destroy most buildings within one mile of ground zero.  The blast wave is also accompanied by strong winds.  These winds may reach speeds of 400 miles per hour.  The blast wave and wind from this bomb probably would kill the majority of the people within three miles of ground zero and injure anyone within six miles.'

The second effect is thermal radiation which vaporizes and bums whatever it meets.  When the nuclear device is set off the immediate result is an enormous amount of heat produced in less than one millionth of a second.  The heat energy has to expand rapidly, and as it does so it vaporizes anything in its immediate vicinity, including the casing of the device itself.  The expansion is so great that the explosion produces a fireball which emits its energy in the form of heat and light to actually produce the thermal destructive effects.  Thermal radiation consists of ultraviolet, visible, and infrared radiation is given off by the 'fireball'.' The ultraviolet radiation is rapidly absorbed by particles in the air, and so it does little harm.  However, the visible and infrared radiation can cause eye injuries as well as skin bums called flash bums.  Between 20 and 30 percent of the deaths at Hiroshima and Nagasaki resulted from flash bums.' A person can be shielded from the effects of thermal radiation by solid non-transparent objects like walls, trees, and rocks.  However, thermal radiation generated by a one-megaton explosion can produce second-degree bums to exposed human skin up to 11 miles from the point of detonation.' Thermal radiation also can ignite such highly flammable materials as newspapers and dried leaves.  The burning of these materials can lead to large fires.  In a widespread nuclear war, the fumes from these fires could pollute the atmosphere.  This would cause a nuclear winter where there will be a decrease in the amount of sunlight and the temperature will drop.

Residual nuclear radiation is given off later than one minute after the explosion.  Residual radiation created by fission consists of gamma rays and beta particles (electrons).  Residual radiation produced by fusion is made up primarily of neutrons." Residual radiation strikes particles of rock, soil, water, and other materials that make up the mushroom-shaped cloud.  As a result, these particles become radioactive.  When the particles fall back on earth, they are known as fallout.  The closer an explosion occurs to the earth's surface, the more fallout it produces.  Early fallout consists of heavier particles that reach the ground during the first 24 hours after the explosion.  These particles fall mostly downwind from ground zero.  Early fallout is highly radioactive and will kill or severely damage living things.  Delayed fallout consists of tiny, often invisible, particles that may eventually fall in small amounts over a large area of the earth.  Delayed fallout causes only long-term radiation damage to living things.

There is also one other little-known effect of the detonation of a nuclear device and that is the one known as the electromagnetic pulse or EMP.  This is a byproduct of the immediate energy release from a detonated nuclear device which, as well as the other effects mentioned above, also has the ability to alter the electrical properties of electrons in the nearby atmosphere.  This can produce intense electrical and magnetic fields which generate so much energy that they can severely affect electronic based equipment and electrical and radar transmissions to the point of destroying equipment circuits, components, and communications." The effects of EMP diminish sharply with distance from the point of detonation, but can still cause damage at ranges greater than those for the other three major phases.

All of these effects present terrifying consequences by themselves, together they display the spectrum. of terror that nuclear weapons contain and cannot be produced by a chemical explosion of any kind.

Hello Jorge,

thank you very much for your answer.

My question was unprecise - I realized it after re-reading. I meant: when a seismic effect is detected (like yesterday)  and analysed we can definitely say, if it was an underground (nuclear) explosion or a tectonic effect: e.g. by viewing on the relation of the seismic P- to  S-waves.  Assume North Korea simulates nuclear  explosions by e.g. conventional TNT to confuse the world - can we determine from the seismic measurements if an explosion is a nuclear or conventional underground explosion?

Regards

Lothar

When you detonate a nuclear device you have all the time release of nuclear materials that can be detected from a very long distance from the site. If you use TNT for the explosion,  then you do not have the release of these materials.