Essay On Seismic Waves

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When the build up of potential energy around a fault line becomes too great, the two blocks of rock slip suddenly past each other as the built-up energy is transformed into kinetic energy. As the blocks of rock are jolted violently an initial shock wave radiates from the area where the slip occurred, also known as the focus. As the rocks continue to slip back and forth, more shock waves are sent out. After the initial slip occurred at a depth of around 6km on the Port Hills Fault, the rupture spread upwards and then towards the northwest, thereby focusing all the energy of the earthquake towards the city.

There are four different types of seismic waves: Primary (P), Secondary (S), Love (L) and Raleigh (R). P waves are the first waves to reach recording stations, which is why they are called primary waves. They travel at approximately 20,000km/h and are a push-pull wave, which means they stretch and squeeze rocks as they pass through. S waves are slower than P waves, travelling at 10,000km/h, therefore arriving after P waves at the recording station. They have larger amplitudes th...

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