Earthquake key facts

The groundshaking as a result of the rocks within the earths lithopshere

hen the crust moves, there is a slow build up of stress within the rock and when it is relased it causes the ground to shake from the realease in energy through seismic waves

Epicentre - the point immediatly above the focus

Focus - The point where the pressure release in the Earth 

shallow earthquake have shallow focus - 0-7km deep causes greatest damage as energy is not dissapted - thesee account for 75% of earthquake energy released

vast majority along plate margins - most powerful being conseravtive and destructive faults

some associated with old fault lines such as the Midlands earthquake in Dudley in 2002 of 4.8 - result of movement on a old fault line called Malvern line

some human acitivty the result such as the Three Gorges Dam reservoir in China

Richter scale measures magnitude (the amount of energy)

• Logarthermic
• each step marks an 10x increase in amplitude in wave and 30 fold increase in energy
• most commonly used
• goes from 0-10

The modifiyed Mercalli  instensity scale measures intensity

• Measures the impact /effect of the quake
• Goes from I- X
• Good for insurance companies - but is subjective
• level I is detected by seisometres but felt by very few people
• Level X is destruction with the collapse of structurs - 8.5 on the richter scale
• based on observed effects

There is no way of predicting exactly when an earthquake is going to happen but there are possible clues people and experts could look out for including

• small tremors pre the major event which can be detected by seimsographs
• strange animal behavior
• monitoring ground water levels
• monitoruing fault line activity
• lookinng at past records
• release of radion gas
• mapping the fault
• monitoring the earths magnetic field
• P waves but only whilst its happened

sceinests have been looking into lubcricating fault lines to stop the build up pressue with oil and water

not sucsesful on a large scale

Earthquake proof buildings - steel jolt joints

fire prevention

aid

government plan

education

risk areas

ensurance land use planning