The theory of earthquakes
Scientists began to study and monitor earthquake activity in earnest in the mid 1800’s using a device called the seismograph which had been developed in Italy.
It wasn’t until the 1960’s, however, that British and American scientists developed a theory as to why earthquakes occur – their theory is called plate tectonics.
It wasn’t until the 1960’s, however, that British and American scientists developed a theory as to why earthquakes occur – their theory is called plate tectonics.
Plate tectonics
http://abyss.uoregon.edu/~js/glossary/plate_tectonics.html
The earth’s crust (lithosphere) is made up of many plates of rock sliding over the lubricating asthenosphere layer. At the boundaries between these plates, they sometimes move apart and molten rock comes up to the surface where it’s called lava. This cools and forms new crust. The site where this happens is called a divergent boundary.
These plates of rock push against each other in other areas. This results in either one of the plates sinking under the other, known as a subduction zone, or the two plates pushing together and rising upwards, forming mountains. This is called a convergent plate boundary.
In some other areas, plates move alongside and grind slowly against each other, building up friction and energy between the rocks. This is called a transform boundary.
These plates of rock push against each other in other areas. This results in either one of the plates sinking under the other, known as a subduction zone, or the two plates pushing together and rising upwards, forming mountains. This is called a convergent plate boundary.
In some other areas, plates move alongside and grind slowly against each other, building up friction and energy between the rocks. This is called a transform boundary.
Faultlines
A faultline is a break in the earth’s crust and will form where plates of crust are moving in different directions to each other.
There are 4 kinds of earthquake faults.
Normal faults – which occur at divergent plate boundaries
Reverse faults and thrust faults – which occur at convergent plate boundaries
Strike-slip faults – which occur at transform plate boundaries
In all these faults, friction is created by the plates pushing together. When there is enough friction built up, the rocks become stuck. The force from the earth continues to push against the stuck rocks, increasing the pressure and creating potential energy. Eventually, if the pressure becomes sufficient, the rocks become unstuck suddenly and move, releasing the built up energy as seismic waves.
The most common places for earthquakes to occur is at plate boundaries because this is where the pressure from plate movements is strongest and this leads to groups of faults connecting together, creating a fault zone. When energy is released from one fault, this can lead to an increase of pressure and build up of potential energy in another nearby fault which may lead to other earthquakes in the future. The earthquake with the largest magnitude is the main shock and any smaller quakes after are called the aftershocks.
There are 4 kinds of earthquake faults.
Normal faults – which occur at divergent plate boundaries
Reverse faults and thrust faults – which occur at convergent plate boundaries
Strike-slip faults – which occur at transform plate boundaries
In all these faults, friction is created by the plates pushing together. When there is enough friction built up, the rocks become stuck. The force from the earth continues to push against the stuck rocks, increasing the pressure and creating potential energy. Eventually, if the pressure becomes sufficient, the rocks become unstuck suddenly and move, releasing the built up energy as seismic waves.
The most common places for earthquakes to occur is at plate boundaries because this is where the pressure from plate movements is strongest and this leads to groups of faults connecting together, creating a fault zone. When energy is released from one fault, this can lead to an increase of pressure and build up of potential energy in another nearby fault which may lead to other earthquakes in the future. The earthquake with the largest magnitude is the main shock and any smaller quakes after are called the aftershocks.