Earthquakes Flashcards
Extent : Magnitude
Magnitude : the greater the magnitude, the more damage done to a place
Magnitude refers to the amount of energy released from an earthquake
It is measured using the Richter scale.
The energy released causes the ground to shake, and that causes buildings and infrastructure to be damaged and collapse.
Extent : Magnitude - example
Example:
The 2004 Indian Ocean earthquake had a magnitude of 9.0 and killed over 200 000 people and caused countless buildings to be damaged and destroyed.
Extent : Population Density
Population density : the greater the population density, the more damage there will be
Areas with a high population density will tend to suffer more casualties than areas with fewer people because more people are exposed to the dangers from the earthquake.
Extent : Population Density - example
Example:
The 2004 Indian Ocean earthquake hit densely-populated areas, and even popular tourist destinations and killed over 200 000 people.
Extent : Distance From Epicenter
Distance from epicenter : the smaller the distance from epicenter, the more damage done
Distance from the epicenter determines how strong the seismic waves are when they reach an area.
Places further away from the epicenter would experience less shaking because energy is lost as it travels through the ground. Thus, less damage is done.
On the other hand, places nearer the epicenter would experience more shaking because there is still a lot of energy released from the earthquake, leading to greater shaking.
Extent : Distance from epicenter - example
Example:
The 2010 Haiti Earthquake (magnitude 7) had an epicenter that was near (16km) from the capital.
As a result the capital was almost completely destroyed with over 200 000 dead.
Extent : Time of occurrence
Time of occurrence : when earthquake occurs at a time when people are not alert/awake, the more damage (more deaths) there will be
The time of day when an earthquake happens determines where people are and what they are doing. This affects their chances of survival during an earthquake.
More deaths occur when people are not alert or awake to react and get to safety during an earthquake
Extent : Time of occurrence - example
Example:
The 1995 Kobe earthquake hit at 5.46 am. Many people were still asleep and caused a death toll of 6400.
Extent : Preparedness of People
Preparedness of people : the less prepared people are for an earthquake, the more damage (deaths) there will be.
More deaths occur when people are not prepared for an earthquake
People would not know what to do or where to go during an earthquake
If they panic, they may endanger themselves and others even more with irrational behaviour
Extent : Preparedness of People - example
Example:
The 2010 Haiti earthquake had a death toll of about 300 000. Haiti has not been hit by an earthquake since the 18th century and many people did not know what to do.
Extent : Type of soil
Type of soil : places with loose, unconsolidated soil will experience more damage
Buildings built on soft (loose and unconsolidated) soil tend to suffer more damages than buildings built on solid rock during an earthquake because soft soil is naturally less stable than solid rock.
As a result, the ground will shake more from the earthquake vibrations, amplifying the energy.
During an earthquake, loose and unconsolidated soil may undergo soil liquefaction, causing structures to topple, fall and sink, causing more damage.
Extent : Type of Soil - example
Example:
Although the epicenter was not very close, the 2010 Christchurch earthquake caused massive damages to the city of Christchurch because of soil liquefaction.
Risks : Tsunami
Tsunami : tsunamis are dangerous because they sweep, engulf, wash, swallow EVERYTHING in its path
An underwater earthquake occurs
Seismic energy from the earthquake displaces and forces out a mass of seawater
Out at sea, tsunami waves are small. They may pass undetected.
On reaching shallow water, greater friction slows down the waves and forces them to increase in height
Large tsunami waves of up to 15m in height crash onto shore destroying and flooding everything in its path.
RIsks : Tsunami - example
Example:
The 2004 Indian Ocean earthquake resulted in a large tsunami that hit many countries that killed over 200 000 people and caused countless buildings to be damaged and destroyed.
Risks : Landslides
Landslides : landslides are dangerous because the land collapses, bringing down everything on it
The shaking of the ground can weaken the slopes of hills and mountains.
The unstable slopes can result in rapid downslope movement of soil, rock and vegetation debris, forming a landslide
Risks : Landslides - example
Example:
For example, an earthquake off the coast of Peru in 1970 destabilized the slopes of Mount Huascaran and triggered a massive landslide that killed 18 000 people in the town of Ranrahirca
Risks : DIsruption of Services
The shaking of the ground can cause power lines and telecommunication lines to break
This can cause further problems because people are not able to communicate and get help
Breakage of power lines can cause short circuits and fires
The shaking of the ground can also cause water and sewage pipes to break
This can cause other problems like fires and contamination of drinking water.
Risks : Disruption of services - example
Example:
Fire broke out during the 1995 Kobe Earthquake due to the damaged power lines. To make things worse there was no water pressure to put out the fire due to water pipes bursting too.
Risks : Destruction of Infrastructure
Destruction of infrastructure : intense shaking causes infrastructure to be damaged and destroyed
The shaking of the ground can crucial infrastructure like roads and bridges to collapse
This can cause problems because people are not able to escape and help is unable to reach the needy
It is also difficult for people to return to normal life or daily commute after the earthquake
Risks : Destruction of infrastructure - example
Example:
During the 1995 Kobe Earthquake, many roads and bridges collapsed, and railways were also damaged.
Risks : Destruction of Properties
Destruction of properties : intense shaking causes homes to be damaged and destroyed
When buildings collapse, people are trapped under the rubble or killed when they are hit by falling debris
Preparation : Land use regulation
Refers to restrictions of development in certain areas to minimize damage, in the event of an earthquake or a tsunami
Preparation : Land Use Regulation - success
Successes:
In California, USA, all new building developments are not built across fault lines and areas at risk of liquefaction.
New buildings are prohibited from being built on low-lying land that is vulnerable to tsunamis.
This is common along the coasts of Japan and North America, where the Pacific Ring of Fire is located.
Preparation : Land Use Regulation - Limitation
Limitations:
It is difficult to implement this in areas that have already been built-up or privately owned.
Private owners may also be reluctant to move even if the government offers compensation, which is already a very costly move
