Discuss the Effectiveness of Two Scales Used to Measure an Earthquake.

An earthquake is a sudden release of energy from the earth’s crust, because of the movement of the tectonic plates, this sudden movement creates seismic waves, and these waves are P, S, L and R. The primary waves, are the first waves to hit the surface, this is because they are longitudinal and travel like sound in short wave lengths, like pushing on a spring, these can also travel though solid and liquid. S waves arrive second because they act more like string being waved, this only travel through solids. These two are not the most powerful, this belongs to the Love and Rayleigh waves which are the last waves to hit, these move the surface in different ways love waves cause horizontal up and down movement of the earth’s crusts, while Rayleigh waves cause a rolling motion, both of these are very destructive and can cause roads to rip up and building to topple over. The power and destruction of an earthquake depends on the depth of the focus, if there is a shallow focus then the earthquake will measure high on the Richter scale, but will only affect a small area of the surface.

The causes of earthquakes are tectonic plates moving suddenly, for example when the plates get snagged and caught on one another. There are two types of plate boundaries which cause earthquakes, convergent and transform. Convergent boundaries which is the pushing together of two plate boundaries and one plate slips under the other, as this happens the plate gets stuck and a sudden jolt of the plate happens when it becomes unstuck, this creates a earthquake. transform plates, which is two plates rubbing against each other, as they are moving across each other they get stuck on protruding rock, as this is broken down, the plate suddenly moves creating a quick and sudden earthquake. An example of a transform plate is the San Andreas Fault; this fault is caused when the Pacific plate and North American plate, this has created many highly powerful and destructive earthquakes along in San Francisco and surrounding areas. A transform plate caused the biggest natural disaster in human history, when the North American plate and Caribbean plate was rubbing against each other and caused a transform plate, this strike slip earthquake caused a 7.0 on the Richter scale and killed 280000 people and left 1.5 million people homeless.

There are two areas that we detect earthquakes, the epicentre and the focus, the focus is the underground