Factors that would affect a person's perception of a given hazard:
- Development of a country- MEDCs tend to have better infrastructure, so are less likely to be damaged.
- How prepared a country/ individual is affects the severity of the hazard (education, socioeconomic status). For example, if citizens are educated about emergencies, they will be able to act quicker. Government schemes and community action helps.
- Past experiences- people will be wary if an even has happened before.
- Knowledge on hazard and risk (which can be provided through education/ awareness raising campaign)
- Willingness and ability to take action to reduce risk.
Risk assessment and management
Risk perception is an important part of the management of any tectonicc hazard, as withoout the perception of a risk, no risk planning/ management can occur. Hazard management tends to follow a system of stages:
- assess the risk
- prescribe action
- educate and inform people
Earthquake hazards- Liquefaction
When soft wet sediments are shaken by earthquake waves, the ground can liquify, causing buildings to subside:
1) Sediments shaken by seismic waves
2) Seismic waves amplify in soft unconsolidated sediments
3) Water saturated sediments compact
4) Water forced upwards
5) Water and sediment erupts onto surface
6) Softened ground surface causes building to subside
Earthquake hazards- Tsunamis
Earthquakes are one of the trigger mechanisms for Tsunamis. The other mechanisms are submarine valcanic activity and submarine landslides.
Eg. Boxing day tsunami 2004- killed more that 225,000 people in eleven countries around the Indian Ocean
1) Elastic rebound of the over- rideing plate at a destructive plate boundary causes the vertical displacement of a collumn of water.
2) From the point of water displacement, waves radiate outwards at speeds of up to 500mph.
3) Upon approaching shallow water near the coast, the velocity of the wave is reduced. This has the effect of shortening the wave kength but increasing the wave height.
4) The wave can break at the coast and travel inland for distances of over 1 mile. This caused damage to buildings and property, which is increased further when the wave receeds, transporting debris with it.
5) The above can be repeated numerous times.
Earthquake hazards- Ground shaking and landslides/
Ground shaking causes building to collapse. It is often ssid that it is buildings which kill people, not earthquakes.Eg. The 7.0 RS earthquake in Haiti on 12th January 2010 destroyed 50% of the buildings in Port-au-Prince and killed over 200,000 people.
Earthquakes often act as trigger mechanism for slopes to fail. Eg in 2005, a landslide damaged a Pakistan villiage.
Magnitude of earthquakes
Where seismograms detenct an earthquake, its magnitude is recorded. The magnitude of an earthwuake refers to the ampitude of its shock waves recorded on a seismograph. Magnitude is classified on the Richter Scale, which ranges from 1-9. The scale is logarithmic (eg. magnitude 6 is 10 times greater than magnitude 5).
It no seismograms are in the area, the intensity of an earthquake can be represented by the degree of surface shaking according the the Modified Mercalli Scale. This scale is a qualitative scale.
Factors affecting the impact of an earthquake
Economic development of location:
- MEDCs are likely to have buildings designed to withstand earthquakes. Safety features can be added, which are expensive.
- LEDCs can't build to the same standard as MEDCs- poor construction.
- MEDCs have disaster plans- government departments and educating citizens.
- MEDCs are self reliant. They can keep emergency stocks as spare, while LEDCs have to ask for help, which may take days.
Urban or rural area:
- Population density- the damage will be small in a rural area with few people. If there are more buildings and people, the damage will be greater.
Distance from the epicentre:
- The power of the shockwaves decreases with didstance from the epicentre.
- The most damage will happen near the focus- stronger seismic waves.
Landscape and rock type:
- Liquefaction can occur and make buildings fall. Harder and more solid rocks such as granitee won't liquify, so are safer.
- Earthquakes with epicentres on the seabed may trigger a tsunami.
- Mountainous areas have unstable steep slopes, meaning landslides can be triggered.
Factors affecting the impact of an earthquake
Weather and season:
- If people are left homeless/trapped, they are more likely to die in cold wet weather- hypothermia, frostbite, etc.
- Bad weather makes rescue efforts harder.
- Cold weather increases the chance of fires, as people keep their fires/stoves on.
- High temperatures make it hard for trapped people to survive- dehydration.
- Warm weather speeds up the decomposition of dead bodies, which become sources of bacteria and spread diseases.
Time of day and day of the week:
- In cities, many people are gathered during the working week in vulnerable buildings (eg. high rise office blocks).
- During the weekend, people are moe dispersed so less people are likely to be killed.
- At 3am, people are lying down in bed, spread across a wide area and protected by bedding etc. At 8am or 5pm, they would be travelling (cars, trains) or walking around. They would be more vulnerable.
Emergency services and earthquake response plans:
- Developed countries usually have better trained and funded emergency services. They will have planning regulations, which LEDCs won't have.
Earthquake management- prediction
Although, to some extent, we can preduct the location and intensity of earthquakes, we cannot predict the exact timing of them. It is an imprecise science.
In Southern California, geoscientists are looking at the patterns of previous earthquakes . A long priod of time between earthquakes indictates that there is pressure building up. They map the frequency of previous earthquakes to identify areas of risk. They identify areas of high risk based on the rock type. Areas with soft sediment will shake more and for longer.
This is not the best way of earthquake management.
Earthquake management- aseismic building design
90% of deaths from earthquakes are from building collapse.
- Rubber shock absorbers between foundations and superstructure.
- Automatic shutters come down over windows to prevent pedestrians being showered with glass.
- Reinforced latticework foundations deep in bedrock.
- Rolling weights of roof to counteract shock waves.
- 'Birdcage' interlocking steel frame- can bend, ductile.
A tuned mass damper system in Taipei 101 in Taiwan:
- Tuned mass dampers are huge concrete blocks mounted in skyscrapers or other structures. They are designed to move in the opposite way to the resonance frequency oscillations of the structure.
- Taipei 101 needs to withstand typhoon winds and earthquake tremors common in the area od the Asian Pacific. A steel pendulum weighing 660 metric tonnes was designed and installed atop the structure. It is suspended from the 92nd to the 88th floor.
LEDCs cannot afford these strategies. Instead, they have:
- Buildings with light rooves- less weight pushing down and is less likely to collapse.
- Strong, reinforced corners- they are often the weakest parts.
- Flexible building materials- won't collapse or crumble (wood and straw bales).
Earthquake management- land use planning
This can be used to identify the most hazardous areas in the event of an earthquake, which can then be regulated in terms of buildings and usage. Certain types of buildings, such as hospitals, should always be located in low risk areas.
Providing sufficient open spaces between buildings is important because:
- People can evacuate to these areas of safe refuge.
- Staying in a building is dangerous because fires can occur after earthquakes, which can put people in danger. Aftershocks may cause further collapse.
- Open spaces can be used as a firebreak to stop fire spreading in an urban area.
- A building in Tokyo called ‘The Wall’ has hoses attached to it that spray water onto the open space.
Liquefaction in San Francisco:
- Places of low susceptibility should be where development occurs.
- Areas of high susceptibility should be avoided for future development. They may be left as areas of open space or parkland.
Earthquake management- community preparedness
By educating the population of a high earthquake risk zone about the procedures to follow in the event of an earthquake, the number injured and killed be reduced. In Japan, 1st September every year is ‘National Disaster Prevention Day’ during which both the emergency services and the general population practice hazard drills. They give advice, such as turning off stoves and heaters, hiding under a table, stopping driving and evacuating. California has recently run an earthquake drill called the ‘shake out’, involving over 5 million people.
This type of management strategy is more difficult to apply in an LEDC because:
- A lot of community preparedness resources are online, so citizens can’t access them.
- Many governments in LEDCs lack the funds to make campaigns like this.
- Poor people may not have the money for things like safety straps to prevent things from falling. People have priority for food and school, not improving the house.
Earthquake management- emergency/ relief services
In many MEDCs such as the USA and Japan, well established procedures are in place to deal with an earthquake event. This involves:
- Police, fire brigade, ambulance, specialist search and rescue teams, the army, etc.
- Health provision: paramedics, hospitals
- Emergency shelters and accommodation
- Provision of food and water
- Utilities: water, electricity, gas supplies will be fixed and managed.
- Clean up and rebuild
- Insurance claims to cover costs
In LEDCs, the emphasis is often on dealing with the aftermath of an earthquake event. Due to financial constraints in the home country, help from Non- Governmental Organisations (NGOs) such as international charities is often sought or needed. The DEC gives donated money to aid organisations (eg. Red Cross, Save the Children, Oxfam). They then coordinate the roles of the aid organisations.
Loma Prieta earthquake- social and demographic imp
- 63 deaths (42 from Cypress Freeway)
- 3757 injured
- 12,053 displaced
- The Cypress Structure section of Interstate 880 was built on unstable marshland and was made of non- ductile reiforced concrete. The collapse disrupted the 170,000 vehicles that travel on it each day.
- The Bay Bridge is .5 miles long and is made of double-decked steel. The collapse of a section of the upper deck forced the bridge to close for one and a half months. 250,000 vehicles used it a day.
- State Highway 17 had disrupted traffic for about 1 month.
- Railways disrupted.
Loma Prieta earthquake- economic and environmental
- $6.8 billion direct damage
- 2600 businesses damaged, 147 destroyed.
- It took 9 years and $1.2 billion to rebuild the Cypress Freeway.
- Replacement of gas pipelines in the Marina District cost $20 million.
- 12,000 homes damaged, 963 destroyed.
- Damage and business interruption- $10 billion.
- The San Francsisco water department experienced 70 water main breaks and 50 service line breaks in the Marina District.
- 20 million gallons of raw sewage was dumped into the Oakland esuary in 6 hours.
- More than 1000 landslides and rockfalls in the Santa Cruz mountains.
- LIquifaction in the Marina District (it was built on landfill and rubble from the 1906 earthquake with lots of groundwater).
Future risks and hazard perception in California
There is a great risk of a migh magnitude earthquake affecting the Southern California area, including Los Angeles in the future. The potential impacts are:
- 1800 deaths
- 50,000 injured
- $200 billion damage
- No water for a month- water systems would be destroyed.
There is a greater than 99% probability of a major earthquake affecting Southern CAlifornia in the next 25 years.
Why do people choose to live in a hazard risk zone?
- The high tech IT industry are more profitable and are based there- lots of well-paid employment.
- People presume that the earthquake will be managed, so won't severely affect them.
Haiti earthquake- causes
16:53 local time, Tuesday 12th January 2010
Physical (tectonics and geoology):
- Haiti lies on a conservative plate boundary which seperates the North American Plate and the Carribean plate.
- The North American plate is moving past the Carribean plate at a strike slip fault. The plates lock against each other along this fault and eventually, when enough stress has built up, the plates move suddenly. This releases the stress and produces an earthquake. The epicentre was only 15km south-west of Port-au-Prince, the capital city. It measured 7 on the Richter scale.
Haiti earthquake- causes
- Building design- 86% of the population of Port-au-Prince were living in tightly packed slum condidtions. Housing was very poor quality with little or no aseismic design. Modern concrete structureswere built using cheap construction techniques. Not enough reinforcing steel rods were built into the concrete, leading to collapse.
- Land use planning- There was no planning to take into accunt earthquakes. Crowded conditions meant that when buildings collapsed, there was rubble in the streets. This hindered movement and rescue. There was no consideration given to building on soft sedimentswhich amplified ground shaking and led to building collapse.
- Community preparedness- 80% of the schools were poor quality. Literacy levels were poor. Most people had recieved little or no earthquake training and did not know what to do when the quake struck. No earthquake drills were in place.
- Emergency/relief services- Many of the hospitals wer destroyed or badly damaged by the earthquake. The emergency services were not sufficiently trained or resourced to deal with the crisis. The airport damage made it impossible for rescue flights to land and bring help. Liquefaction in the port area meant that the harbour was out of action so emergency help via sea was not initially available.
Haiti earthquake- impacts
- 3,500,000 people were affected by the quake, 2.8 million of these were in the capital Port-au-Prince.
- 222,570 estimated deaths
- 300,572 people were injured
- 1.5 million became homeless
- Over 180,000 houses were badly damaged.
- Over 600,000 people left their home area in Port-au-Prince and mostly stayed with host families.
- Many government officials were killed, so few people were left to organise and manage the relief effort.
- 1.5 million homeless people ended up living in camps wih few facilities- loss of dignity.
- 100,000 were vulnerable to storm and flooding.
- 1,100 camps were set up, 54 of which housed over 5,000 people.
- 4,000 schools were damaged or destroyed, including 80% of the schools in the capital and 60% of in Haiti.
- 25% of civil servants in Port-au-Prince died and 60% of government and administrative buildings destroyed.
- There was an outbreak of cholera in October 2010. By July 2011, 5,899 had died and 216,000 were infected.
- Security and crime risks- city jail was destroyed.
- Port-au-Prince Cathedral was destroyed along with others. Spiritual focus was lost.
Haiti earthquake- impacts
- US$7.8 billion ($4.3billion of physical damage and $3.5 billion of economic losses). The damage and losses are equivalent to 120% of the 2009 GDP.
- Rebuilding of homes is costing an estimated $2.3 billion.
- Most facories were destroyed, impacting on exports.
- $3.5 billion given in foreign aid. The financial contribution of the EU as a whole was $330 million.
- The world bank waived Haiti's debt repayment for 5 years.
- Individuals- Eg Angelina Jolie and Brad Pitt and Leonardo DiCaprio donated $1,000,000 each.
- Over 1,000 military and disaster relief personnel were sent from the USA, the UK, Canada etc.
- The USA took charge of coordnating aid distribution, while Medicines San Frontiers helped casulties.
- There was 19 million cubic metres of rubble and debris in Port-au-Prince.
- Many roads were blocked by rubble or landslides, hampering relief efforts.
- Destruction of the harbour area and airport runway also hindered relief efforts.
Iceland- positive perceptions of tectonic hazards
Icelad is located on a contructive plate boundary and therefore experiences regular volcanic eruptions and earthquakes.
- In 2000, there were 302,900 visitors.
- In 2010, there were 488,600 visitors.
- 86.3% of visitors to Iceland are for holiday reasons.
- 63% of peole visit because they are interested in the nature of the country.
- Gesir- geothermal energy causes groundwater to shoot up out of the ground.
- Thing vellir- rift valley- people can walk across the American and European plate boundary.
Geothermal energy use-
- Hot springs provide heat to 89% of homes, produce 4,600 GWh of electricity, provide heat for swimming pools and cooking, heat water for ocean and shore based fisheries,and heat greenhouses to grow various plants and food crops.
- Blue lagoon- heated outdoor pools
- All houses in the capital city are heated by geothermal energy.