The Processes Of An Earthquake.
There are many processes which form an earthquake and that occur during it. First of all, tension builds up between tectonic plates as they collide or move past, or away from each other, these plates are driven by convection currents in the semi-molten layer below the crust. The plates slowly drift over Earth’s surface. Most earthquakes occur on fault lines which are cracks in Earth’s crust and travel in seismic waves. There are three types of seismic waves, Primary (P waves), Secondary (S waves) and Surface (Which include Love waves ((L waves)).) These waves are released from an Epicentre which is the The primary waves are the first to occur, these waves travel fastest and create a longitudinal movement. They can move through both, solids and liquids. The primary waves are the cause of the rumbling sound that occurs before you feel the actual Earth shake, these waves create the sound energy through vibrations that push and pull particles making sound, they also move very fast at the highest velocity, and therefore the sound arrives first. Secondary waves occur second and these are the waves that cause the ground to shake/move up and down. They are only able to move through solids. With S waves, the particles move in a transverse motion to the direction of travel and this results in the rock becoming distorted and moved about.
As a result of secondary waves, damage to the environment occurs. This can include, liquefaction, tsunamis and damage to buildings depending on where an Earthquake occurs. In the case of the Christchurch earthquakes, liquefaction and damage to buildings occurred. Liquefaction is the process of soil particles liquefying because they have been disturbed by secondary waves and then they re-arrange, meaning that soil mass compacts and decreases in volume, allowing water to come to the surface of a land area. this can cause a lot of damage because it can create splits in the lithosphere, resulting in sand boils, volcanoes and buildings to have un-even ground to stand on. The reason a tsunami didn't occur for either of the Christchurch Earthquakes is because the earthquake occurred along the Alpine fault near Christchurch but not the coast of New Zealand meaning there would insufficient water supply to cause a tsunami.