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‘Earthquakes generate only local hazards.’ Discuss. (33 marks)
An earthquake is caused when pressure builds up on a plate boundary. Earthquakes can happen on all three boundaries and cause hazards such as tsunamis, liquefaction and flooding. Although plenty of the dangers caused are local, earthquake hazards are not confined to a local scale.
Earthquake tremors and shaking cause many problems for areas close to the epicenter. Cracks in the land and land movement can disrupt infrastructure and buildings near or on the fault line. Underground structures like water pipes and electricity cables can also break- which may lead to a fire hazard as it did in Kobe, Japan where pipe leakages caused over 300 fires. Apart from fires, pipe damage can cause water shortages which can spread further than the areas close to the epicenter. While these effects can severely damage the economic and social sectors of an area, they are relatively local compared to some global problems which can be caused by earthquakes. The type of rock an area is built on can also affect the level of damage caused by the earthquake as some rock types can amplify seismic waves more than others- the more solid the rock is the less the waves will be felt.
A local factor of earthquakes is liquefaction. This process occurs when the tremor of an earthquake causes land with a high water content to turn from solid to liquid. Liquefaction can cause massive infrastructure damage as is seen in the Kobe earthquake in Japan, which badly affected the land around the port. Cars and buildings sunk into the land and collapsed. Reclaimed land- land which would have been underwater had it not been protected by humans, has an especially high chance of liquefaction as the water content of the land is very high. This process is dangerous but very local, spreading only to nearby land with plenty of water.
The hazards of an earthquake can be emphasized depending on where the epicenter is regardless of the magnitude of the quake. The Haiti earthquake near the capital Port-au-Prince which killed 250,000 people had a far more devastating effect than an earthquake in New Zealand which occurred underwater resulting in no fatalities. Both earthquakes had a magnitude of 7 but Haiti suffered much more damage than New Zealand.
Landslides can cause multiple local issues. As they can be caused by even small magnitude earthquakes they pose a big hazard if near a densely populated area. The Himalayas are often affected by landslides and can be triggered by vary small earthquakes because of the mountains’ steepness. Landslides can kill climbers and block streams or rivers making a natural dam. Once this dam overfills a large flood can be released downstream which can affect more people than the landslide itself.
Underwater landslides can create tsunami-like waves which are devastating to areas near the wave. As these waves are generated on a local scale, they travel to land in less time than tsunamis do, leaving little to no time to warn people to evacuate. As a result underwater landslides cause a large death toll such as that of Papua New Guinea which killed 200 people.
Tsunamis are probably the biggest global problem as the result of an earthquake. They are caused when a convergent plate boundary gets stuck, and the jolt which sends the plates back into movement, flicks the less dense plate up. When the plates are underwater the water on top of the plates also gets pushed up creating large waves in all directions. As tsunami waves travel through oceans, they become more dangerous as the shallower waters cause the waves to rise higher. The magnitude 9 earthquake near Sumatra in 2004 caused tsunami waves to be released in all directions particularly affecting the Aceh region (locally), the Indian Ocean and Somalia (global). This tsunami killed over 5000 tourists and many more people living in the affected areas. A similar tsunami in 2011 japan affected not only the Japanese region but also created a large economic cost for Hawaii and California.
Although the worst damage by earthquakes is done to local areas; it is not true that this is the only damage done. The global damage is especially prominent in the social and economic sectors as seen in the Haiti earthquake, which triggered a global fundraising trend to help Haitians, many of who had lost family and friends to the earthquake.