With reference of one or more examples of earthquakes, assess the extent to which attempts at prediction and mitigation may have influenced the impact of the hazard.
An earthquake is the result of a sudden release of energy in the Earth’s crust that creates seismic waves. Earthquake is a major threat to the human and natural environments, in which people died, buildings collapsed and cities destroyed. Prediction and mitigation are usually conducted in order to reduce the impact of an earthquake on environment. Earthquake prediction can be carried out with seismic monitoring using tiltmeters. Hazard mapping is another way to predict the impact of an earthquake and can be used for planning purposes. Mitigation includes the aseismic building design, land-use planning, community preparedness as well as insurance and aid. With a few examples on prediction and mitigation, it is clear that successful prediction can largely reduce the impact on human environment although few have succeeded so far; but mitigation can be carried out before the earthquake and can also alleviate the human losses. However, the influence on physical environment is not as significant as that on human environment.
Haicheng Earthquake in 1975 was the first successful example of earthquake prediction in history. It is located in Liaoning, Northeast China and the earthquake caused more than 2 000 fatalities. In 1970, Liaoning was listed as one of the key areas for earthquake monitoring and protection by China Earthquake Administration (CEA). A few geologists predicted that a major earthquake with magnitude larger than 6.0 was going to occur in 2 years in this region. Middle-term (2~3years) and short-term (2~3months) forecasting was conducted and the local government announced several earthquake preventive measures in January, 1975. Factories, and companies were closed down; all entertainments were banned to ensure people’s safety. In the preceding months, changes in land elevation and groundwater levels, and peculiar animal behaviour had been reported. Warnings were issued through radio and broadcast. Chinese officials ordered the evacuation of Haicheng the day before the earthquake. The evacuation saved more than 150 000 lives. According to CEA, this successful prediction and mitigation helped avoid nearly RMB 1 billion losses. Thus, the successful prediction and effective mitigation can largely reduce the impact of earthquake on human environment, in particular, the death tolls and economic losses. However, it can barely alleviate the impact on physical environment.
However, not all the earthquakes can be accurately predicted. The unexpected 2004 Indian Ocean earthquake killed more than 283 100 people, the majority of the victims were killed by the huge tsunami triggered by the earthquake. The tsunami affected a wide region, including the east African country, Maldives, causing death and damage to the natural environment. At many unprotected coasts near Sumatra, rise of sea water creating surges that were faster than people could run. Many coastal towns were almost completely destroyed by the huge waves. At that time, there were no tsunami warning systems in the Indian Ocean to detect tsunamis or to warn the general populace living around. Furthermore, predicting earthquake is also very tough. Due to the nature of the earthquake hazard in which it is a sudden release of large amount of energy, the process may be so fast that once it is detected, it occurs, leaving little time for evacuation to be done. Setting up the communications infrastructure to issue timely warnings is an even bigger problem, particularly in a relatively poor part of the world.
As the prediction is too difficult to be carried out or the prediction may not be accurate and certain enough to conduct mass evacuation as a false prediction may make a turmoil among people, mitigation is more realistic and effective in this case. By studying the previous earthquake events,...
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