Case Study of an Earthquake in an LEDC - Bam 2003

Bam, the ancient historic city in Iran, was hit by an earthquake measuring 6.6 on the Richter scale on December 26th, 2003 resulting in the deaths of over 43,000 people and leaving over 60,000 people homeless. Many of the mud-brick buildings in Bam collapsed resulting in the high loss of life. The mud-brick disintegrates easily into rubble, making rescue difficult and hopes of survival low. The survivors had not only lost friends and family, but their homes and everything else they had. Many were left destitute on the streets, some forced to spend the cold nights wrapped in blankets; whilst some were given tents, others made use of any shelter they could find. 90% of the buildings in the ancient citadel was completed destroyed (photo shows view over the city prior to the quake.

After the quake there was criticism of the coordination of relief efforts by the government and of the lack of preventative measures. The Iranian press spoke out about the controversy surrounding this and the lack of a national plan to make buildings quake proof. Read more about this in this excellent article from the BBC. One of the big criticisms by the domestic press and independent organisations at the time was over the sub-standard housing (with many people dying in collapsed buildings) calling into question the role of the Minister for Housing.

Following the quake in Bam, 'tented cities' were constructed on the outskirts of the city by relief workers to try and house the many homeless. Many survivors were however reluctant initially to leave the sites of their destroyed homes with family members, friends and property still buried. As well as battling to survive in the below freezing temperatures of the Iranian winter, one of the concerns at the time was over the lack of access to decent sanitation, with many sharing outside toilets and a lack of clean water. However, ironically it is believed that the freezing temperatures may have actually helped to reduce the incidence of water bourne disease expected. With large numbers of volunteers coming in from all over Iran after the quake, the main plea for help after the earthquake was for medicine and equipment to help the tens of thousands injured in the quake.

You need to be aware of the reasons for differences in earthquake impact between countries at idfferent levels of development and you need to be prepared in an exam to discuss the differences with examples. So why was the death toll of the Bam earthquake so high? See this excellent articles from the Guardian "Dangerous buildings, lax rules: why Bam death toll was so high" and "Why did so many have to die in Bam?"

Here is a summary of some of the reasons for the high death toll (see article and links below for further detail)

• - poor construction of buildings
• - lack of earthquake proof buildings
• - buildings made of mud-brick (collapse easily into rubble)
• - lack of enforcement of building codes / regulations
• - lack of research into techniques to protect the buildings from earthquakes
• - population boom and competition for houses (resulted in rapid building of sub-standard housing)
• - lack of national plan for the event of a disaster
• - extreme cold temperatures made conditions for survivors difficult
  

To find out more about the quake, including the effects and considerations as to why the effects may have been so severe try exploring some of the following links and news stories:

- Twin Earthquakes - comparing the California and Bam earthquakes of 2003
- Why did the Bam Earthquake Happen (some excellent links thanks to Noel Jenkins of Court Fields School)
- Preliminary report on the Bam Earthquake - Iran
- Bam: Iran's Ancient City (includes photographs and further information)
- Lessons learnt on the national and international response to the Bam earthquake
- Iran Earthquake - Preliminary Reconnaissance (Using Remotely Sensed Data the Views (Visualising the impacts of earthquakes with satellite images) system) - some amazing before and after images here). and also a very detailed report here ICG Report - Bam Earthquake - December 2003

News Stories from the time (BBC News)

The Earthquake: Causes / Effects / Responses:

Bam: Jewel of Iranian Heritage

Tending to Iran's shattered City
Iran battles to cope with disaster
Concealed fault caused Bam quake
Starting from scratch in Bam
Iran lowers Bam earthquake toll
Rebuilding Bam 'could cost $1bn'
Iran considers moving capital
Bam: a year after the earthquake (includes video clips)
Iran quake survivors battle cold

Rescue Missions / Helping the people of Bam:
Helping the people of Bam (work of aid / relief workers to help survivors)
Devon rescue team on Quake Mission
Helping the people of Bam
Woman helps reunite quake survivors (story of a red cross worker)
Iran Earthquake - How to help (what was needed in the immediate aftermath - who helped?)
Earthquake Rescue (audio tale of Phil Haigh who has been working in Disaster Relief since 1968)
Response to the Earthquake / Controversy over lack of Preparedness:
The politics of earthquakes
Iran press lambasts quake efforts
Tough questions over Iran quake
Press tackles Iran over quake
Earthquake angers Iran media
Survivors recall Iran quake loss

Pictures:
In Pictures: Bam before and after
In Pictures: Symbols of Hope
Your Pictures: Bam after the earthquake

Original source of photo: http://commons.wikimedia.org/wiki/Image:BAM_IR2726.JPG

Earthquakes

The cause of Earthquakes

Earthquakes are sudden ground movements which result from the sudden release of built up energy. This energy is released in the form of seismic waves. Earthquakes are caused due to tectonic motions in the earth's crust. Earthquakes are found at all four of the major plate boundaries (constructive, destructive, collision and conservative boundaries), due to the forces of collision between plates as well as the irregular movement and build up of friction as plates move past each other. Earthquakes also occur away from plate boundaries at weaknesses in the earth's crust known as faults.

As plates move past each other, friction between them results in the build up of pressure. As the plates continue to move and the pressure builds up, eventually the pressure is great enough to overcome friction and the plate jolts forward releasing the pent up energy in the form of seismic waves. The point at the rocks break apart and shock waves start is known as the focus of the earthquake. The point on the surface directly above the focus is known as the epicentre of the earthquake. For further explanation of how earthquakes occur, see this excellent animation from the BBC.

Measuring Earthquakes

We measure the magnitude (strength) of an earthquake using a seisometer, the results of which are recorded on a seismograph. To see how a seismograph works, watch this excellent animation. The magnitude of the earthquake, reflecting the energy released, is measured on the Richter Scale (from 1-10). This is a logarithmic scale and therefore each point on the scale is 10x greater than the previous one. Therefore an earthquake measuring 8 on the richter scale is 10 times more powerful than an earthquake measuring 7 on the richter scale.

The Effects of Earthquakes

The effects of earthquakes are far ranging and often involve death and destruction. In 1906, a particularly large earthquake, measuring 8.2 on the Richter scale hit San Francisco (California, USA). Whilst at the time around 500 deaths were actually reported, the actual figure is believed to be around 3,000, the largest death toll from a natural disaster to be recorded in California. Although the actual shaking of the ground during the earthquake was incredibly damaging, it is estimated (wikipedia source) that 90% of the destruction was caused by the severe fires (see photograph) which raged following the earthquake, many starting as a consequence of ruptured gas mains.

We can divide the effects of an earthquake into those known as the primary effects and those known as the secondary effects. Primary effects of an earthquake are those resulting directly from the earthquake itself. These include; buildings collapsing; roads cracking; bridges giving way; shattering of glass and injuries / deaths resulting from these. Secondary effects are those that result from the primary effects. For example ground shaking may result in the cracking of gas and water pipes (primary effects) this can result in severe fires due to explosion from escaping gas and difficulties in putting out fires due to lack of water from burst mains (secondary effects). Other secondary effects include, homelessness, business going bankrupt and closing etc.

You need to learn a case study of the causes and consequence of a major earthquake - see post on the 1989 San Francisco earthquake.

Follow up links:
USGS - The Richter Magnitude Scale
National Earthquake Information Centre
Earthquakes - General interest publication from the USGS
Wikipedia - 1906 San Francisco Earthquake
Discover our Earth - Earthquakes
How earthquakes work
Understanding Earthquakes
Earthquakes do occur in Britain - see the British Geological Survey site Earthquakes in the British Isles
Map of recent earthquakes in the UK (BGS)
Earthquake Animation

Key Term Check:
Earthquake - a sudden ground movement
Epicentre - this is the point on the surface directly above the focus of the earthquake
Fault - a weakness in the earth's crust where an earthquake may occur
Focus - this is the point underground where the earthquake starts
Richter Scale - a logarithmic scale used to measure the magnitude of an earthquake
Seismic Waves - waves of energy released in the event of an earthquake
Seismograph - used to measure seismic waves released during an earthquake

Plate Boundaries

Plate Boundaries

The point at which two tectonic plates meet is called a plate boundary. It is at these locations where tectonic activity results in earthquakes, volcanoes and the formation of mountain ranges due to the movement of the plates. The diagram below shows the major plates and their boundaries. The arrows indicate the direction of movement at each plate. It is the direction of movement as well as the difference in crust which determine the variations in processes and landforms at the different plate boundaries. (animation from USGS)

There are a number of different types of plate boundaries. For each plate boundary you will need to be able to describe (i) the movement (ii) processes which occur and (iii) an example

1. DESTRUCTIVE BOUNDARY (also known as a convergent boundary)
Movement: Two plates moving towards each other (continental and oceanic crust)
(note where two oceanic plates meet one will be subducted and an island arc will form)

Processes: The denser oceanic crust is subducted underneath the continental crust forming a subduction zone and oceanic trench. As it is subducted it melts due to heat and pressure. The heat sources are friction between the two plates and from the earth's interior. Melting of the subducting plates creates magma which is lighter than the mantle and therefore rises resulting in the formation of volcanoes. Earthquakes also occur at this type of boundary due to the friction and pressure during subduction.

Landforms Created: Fold Mountains and Ocean Trench

Example: South American and Nazca Plates (forming the Andes and a deep sea trench (Peru-Chile trench))

Animation: click here to see an animation of the processes at a destructive plate boundary (with thanks to Wycombe High School)

2. CONSTRUCTIVE BOUNDARY (also known as a divergent boundary)
Movement: two plates moving away from each other (see animation opposite - courtesy of USGS)

Processes: As the two plates separate, hot magma is able to rise to fill the 'gap' creating new crust. As magma continues to build up, new mountain ranges form under the sea creating a mid-oceanic ridge. Where rising magma continues to build up above the ocean surface, a volcanic island is formed (for example Surtsey, Iceland). Both earthquakes and volcanoes occur at this type of boundary.

Landforms Created: Ocean Ridge; Volcanic Islands

Example: North American and Eurasian Plate - (forming the Mid-Atlantic Ridge)

Animation: click here to see an animation of the processes at a constructive plate boundary

3. COLLISION BOUNDARY
Movement: two plates moving towards each other (both continental crust)

Processes: As both plates consist of continental crust they both resist subduction and buckle and fold, being forced upwards to create fold mountains, such as the Himalayas. Although there is no volcanic activity at these locations, due to the forces of collision major earthquakes often occur here.

Example: Indo-Australian and Eurasian Plate (forming the Himalayas)
Animation: Click here to see an animation of the processes at a collision boundary

4. CONSERVATIVE BOUNDARY
Movement: two plates moving alongside each other

Processes: crust is neither created or destroyed here but as both pressure and friction results during the movement of the plates side by side, a 'stick-slip' motion results in the creation of significant earthquakes. Pressures builds up due to friction between the plates and when the plates break apart the energy is sent through the earth as seismic waves in the form of an earthquake.

Example: San Andreas Fault - North American and Pacific Plates

Animation: See this BBC visualisation of the San Andreas Fault conservative boundary

HOTSPOTS
You should be aware that whilst most volcanoes / earthquakes occur along plate boundaries, there are exceptions. For example the volcanic Hawaiian islands which can be found in the middle of the Pacific Plate are formed due to a Hotspot. Hotspots are plumes of molten rock which rise underneath a plate causing localised melting and the creation of magma resulting in volcanic activity. See this animation for further explanation of hotspot activity.

Follow up Links
An excellent site from the USGS called "Understanding Plate Motions" provides further information
A Flash animation showing the major plate boundaries.
Plate Tectonics on Wikipedia also provides a good overview of the processes at plate boundaries

Key Term Check
Constructive Boundary (Divergent) - where two plates move away from each other resulting in new crust being formed.
Destructive Boundary (Convergent) - where two plates move towards each other - in the case of a plate consisting of continental crust meeting a plate consisting of oceanic crust, the oceanic crust will be subducted and destroyed as it is less dense.
Conservative Boundary - where two plates move alongside each other - although crust is neither created or destroyed here, earthquakes usually occur here.
Collision Boundary - where two plates of continental crust move towards each other creating fold mountains.
Volcano - a vent through which lava, ash etc. is erupted (often, but not always cone-shaped)
Earthquake - a sudden ground movement