# To what extent is the impact of an earthquake related to its strength. (30) (OCR A2)

by robrobertbarclaygmailcom (student)

﻿To what extent is the impact of an earthquake related to its strength.

An earthquake is a sudden release of tension between two plate margins, which had a built-up seismic pressure. When two crusts are deformed/displaced due to plate crustal movement in a result of convection currents, tremor can be caused. Earthquakes occur at all plate margins as well as intra-plate locations such as old relic fault lines. The most destructive earthquakes are related to destructive or strike-slip fault. The magnitude/strength can be measured by the Richter scale, which is a numerical scale which is calculated using a seismograph, this scale is logarithmic. The impact caused by an earthquake can be related to physical or human factors.

The location of the epicentre is a physical variable which could be considered. If the location of the epicentre is closer to the Earth’s surface the tremor will be more concentrated; therefore, a greater amount of vibration may cause more destruction. A comparison which supports this variable is between Haiti and Chile. Chile’s earthquake was 8.8 in magnitude however the epicentre was 35 km deep. In contrast, Haiti’s magnitude was seven, but the epicentre was 13 km deep. There were only 400 people killed in Chile which can be considered very little compared to Haiti’s death toll of 230,000. Obviously, there are a lot of different variables that must be taken into consideration when regarding the death toll, but with Chilies earthquake being three hundred times stronger we must consider that the strength of the earthquake is not directly related to the impact.

Geology is another physical variable which could be considered having an effect on the impact. If the earthquakes foci are surrounded by soft sediment, there may be a greater amount of destruction. Soft sediment will amplify seismic waves this is because seismic waves travel faster through hard rock and soft soil as the amplitude of the wave needs to increase to be able to carry the same amount of energy, therefore, creating stronger shaking. Comparing Chile to Haiti; the main focus of Haiti is located on a river delta compared to Chile where there is harder rock because of the Andes mountain range. So, it can be said that the geology is also another variable factor which will affect the impact created by an earthquake.

The duration of shaking is also variable which may cause the impact to be greater. This also includes after-shocks. If it is a longer amount of vibration bonds within infrastructure will become weaker this is because fair is a greater amount of bond movement loosening each particle. Haiti experience 52 after-shocks, all greater than a magnitude of four. Chile only experienced one seismic tremor. Haiti experience 250,000 residences and 30,000 commercial buildings severely damaged and ready for demolishing. In contrast, 500,000 houses were made uninhabitable in Chile, considering Chilies earthquake was 300 times larger and strengthen Haiti’s this ...