Earthquakes are sudden ground shakes caused when energy is released by tectonic forces.Earthquakes are usually generated by:
Colliding plates along convergent plate boundaries
Faulting ehich causes crustal snapping and fracturing
Lateral(shearing) movements of plates
Volcanic eruptions.
Properties of Earthquakes
Focus-The focus is the origin of the earthquake deep underground.
EpicenterThe epicenter lies on the surface just above the focus and areas around it are devasted the most.
Body WavesBody waves travels below the surface .They are divided into Primary and Secondary waves.P waves are faster and travel through gas,liquid and solid while S waves travel slower and through solids only.
Surface wavesSurface waves travel along the surface of the earth and mostly responsible for damaging structures.Seismographs are instruments that record earthquake waves and provide the duration and energy of the earhtquake.
Impacts of Earthquakes
Earthquakes inflict widespread damage to humans, animals and the environment.The epicenter where the earthquake hit on the surface is the most devastating.As the earthquake spread out from the epicenter ,it gradually weakens and areas far away can only feel feint tremors.Earthquake strength is measured by the Richter Scale(logaritmic scale) from seismographs on a scale of 1-10 ,one being the weakest,five moderate and ten the strongest.An increase by one unit represents a 30 fold increase in energy.
Impact of earthquakes
- Lose of livelihoods
- Damage to infrastructure including resident homes,sky scrappers and road networks
- Electricity poles and pylons are devastated
- Fires from electrical sparks
- Bridge and dam burst resulting in floods
- Nuclear and Oil plants are destroyed
- Mass movements such as landslides and avalanches are common
Secondary effects occuring after earthquake
- Tsunamis
- Poverty and hunger especially in LEDCs
- Death due to hunger
- Lack of sanitation leading to cholera endemics
- Homelessness
- Migration and Refugees
- Traffic Congestion
- Financial loses,Millions of dollars invested or borrowed to pay for reparations.
Earthquakes are natural hazards but can become disasters when level of vulnerability is high.Vulnerability can include lack of preparedness,inability to cope(refusing to evacuate), location and high populations(poverty).LEDCs are the most vulnerable to earthquakes.
The poor warning systems,lack of technology to detect sesmic movements all lead to disasters in LEDCs.In addition,early warnings can be implemented but some groups may refuse to evacuate from their place of living leaving them vulnerable.
Economic constrains results from earthquakes leaving a country broke or piled with international debt.After earthquakes hit evacuated groups may face food,water,shelter or sanitation shortages.This can result in starvation or even death.MEDCs are usually prepared for such phenomenons thus the loss of livelihoods is reduced and evacuated groups are offered quality services.
Mitigating the impacts of earthquakes
MEDCs can cope with natural hazards such as earthquakes than LEDCs.The study of seismic activities provide a heads up for early warning systems.In addition,studying the interval of past quakes can help to predict possible present earthquakes.Unusually animal behaviour such as fleeing away from respective habitats can also provide significant warnings of a possible earthquake.Early warnings evacuates the public quickly and also provide time to gather precious posessions.Evacuated groups are given better services eg tents and health services compared to LEDCs.Good cooperation from the public can lessen lose of livelihoods,unlike in LEDCs where tribes can refuse to evacuate fearing the new world.Countries such as Japan build spring like structures made of steel that are flexible compared to brittle materials such as bricks.Shock absorbers that absorb vibrations are also inserted around buidings.Other mitigatory measures
- Sirens
- Buiding wider roads for easy navigation
- Teaching people on how to react when an earthquake strikes(fire drills,earthquake drills)
