Tectonic hazard human impacts

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  • In locations where the level of economic development is low, a lack of education and information may mean that residents are unaware of the risks, particularly if the zone is not very active.
  • In other cases, residents may be aware of the risks but decide to live in the area anyway - perhaps because it offers significant benefits. For some, living in southern California, with its well-paid jobs and pleasant climate, will outweigh concerns about earthquake risks.
  • Some people are unable to move away from hazardous areas, owing to lack of financial resources, or close links to family and tradition.
  • An estimated 500 million peole were at risk from volcanic hazards in 2000. In the past 500 years, more than 200,000 people have lost their lives as a result of volcanic eruptions.
  • The number of deaths in recent years runs at about 1,000 per year, which is far greater than the number of deaths for previous centuries. This rise is not due to increased volcanism but to an increase in the numbers of people populating the flanks of active volcanoes and valley areas near those volcanoes.
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  • Minerals and natural resources. Volcanoes bring valuable resources to the surface, such as diamonds, copper, and gold. Ancient sea-floor volcanoes contributed to huge accumulations of base metals, such as lead, zinc, and copper.
  • Fertile soils. Volcanoes provide nutrients to the surrounding soil, volcanic ash often contains minerals that are beneficial to plants, and if it is very fine ash it can break down quickly and get mixed into the soil.
  • Geothermal energy. Water running through the earth's crust is heated by high-temperature rocks at or near active plate margins, bringing geothermal energy to the surface, where it emerges as hot springs and fumaroles.
  • Tourism. Modern Western culture sees volcanoes as beautiful as well as threatening. Volcanic regions, both active and extinct, generate considerable interest from visitors, which can bring tourism employment to poor and remote regions.
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Human costs

  • Primary casualties. People killed or injured by an earthquake or volcanic eruption. This might be through buildings collapsing, through being trapped in lava, by poisonous gas or by fire. Casualties tend to be much higher in less-developed countries, because of poor construction methods, limited preparedness and less effective warning systems and search and rescue services.
  • Secondary casualties. People who survive the initial incident but are either injured or die because of insufficient resources and lack of emergency medical care. These again tend to be higher in less developed countries.
  • Tertiary casualties. People who suffer from pre-existing medical conditions aggravated by the hazard event. This group also includes those who become ill, and even die, as a result of the post-disaster environment, largely through infectious diseases or profound trauma. In less developed countries this is often the largest group of casualties.
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Economic costs

  • Direct costs. The immediate cost of repairing damage caused by the event itself. In the case of earthquakes, this will often include demolishing buildings fractured by the shock waves and rebuilding from scratch.
  • Indirect costs. Include the loss of earnings caused by disruptions to working life. If the disruption is prolonged, these can become substantial. Increasingly, major natural hazards are causing secondary technological and industrial accidents and emergencies.
  • It is worth noting that in developed countries, major tectonic events tend to cause high economic costs, mainly due to the large investment in buildings and infrastructure. In developing countries they tend to cause a high loss of life.
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  • Number of earthquakes per year varies, but there has been a general increase in the number of recorded earthquakes over time.
  • The increase in the number of seismograph stations across the world over the last 25 years, along with improved global communications, means more lower-intensity earthquakes have been detected than in the past. By limiting the range to earthquakes of more than magnitude 7.0, which would have been detected in earlier years, we can eliminate this distorion.
  • Between 1986 and 1996, the US Geological Survey listed 15 earthquakes of magnitude 7.0 or greater. This is not markedly different from earlier periods of the twentieth century, which had an average of about 18. But between 1997 and 2007 there were 99 earthquakes of this magnitude: a more than six-fold increase on the previous period and a significant rise compared with any earlier decade in the twentieth century.
  • The number of volcanic eruptions, however, does not seem to be increasing over time. 
  • Comprehensive reporting and recording has been in place since 1960. The trend has been very flat during this period, with a range of between 50 and 70 volcanic eruptions per year and a mean of 58.
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  • There has also been a noticeable trend in the impact of earthquakes over time. The number of fatalities has been increasing since the 1500s. This can be attributed to the increasing global population. When taken as a population, the proportion of fatalites has decreased since 1955 and is predicted to continue declining in the future, due to improvements in preparedness.
  • The impact of tectonic hazard can also be seen to vary over time in the short term. When a hazard event strikes, it disrupts economic and social life, often immediately and totally. The Park model describes a sequence of three phases following such an event.
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Park's model


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Park's model explained

  • Relief phase. Teams from outside the immediate area arrive to help with search, rescue and care operations. Urgent medical supplies, rescue equipment, clothing and food may be flown in.
  • Rehabilitation period. This might last for several weeks or months. Actions are designed to restore physical and community structures at least temporarily. Rehabilitationis more complex than relief, and requires accurate assesment of needs and coordinated planning of responses, This is normally carried out locally. Only in exceptional circumstances (e.g. the Asian tsunami of 2004) are international initiatives involved. 
  • Reconstruction perios. Permanent changes are introduced to restore the quality of life and economic stability to its original level, if not better. The nature of these activities and the speed at which they are carried out are dictated by the type and magnitude of the event and the availability of contingency planning for disasters.
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