EARTHQUAKEALBA ARRANZGARCÍA

4ºA

What is an earthquake?It is a sudden, rapid shaking of the Earth

caused by the breaking and shifting of rock beneath the Earth´s surface and it creates seismic waves.

http://www.youtube.com/watch?v=-zNyVPsj8zc&feature=related

How we measure earthquakes?We can measure the magnitude and the

intensity of an earthquake and we have a scale for each one.

Richter scale: Is a seismic scale which measure the magnitude of an earthquake.

Mercalli scale: Is a seismic scale which measure the intensity of an earthquake.

The instrument that is used for measure an earthquake is called seismograph.

Where earhtquakes occur?Earthquakes usually occur in plate

boundaries (Convergent, Divergent and Transform) and faults ( Normal, Reverse and Strike-slip).

The Hypocentre or focus is the point inside the Earth where the earthquake occur.

The Epicentre is the first place on the surface of the Earth where the seismic waves arrived.

TIPES OF WAVESP waves:-Primary waves-Compresional waves-Longitudinal in nature-Are pressure waves

initial in earthquakes-Could travel through

any tipe of materia-They travel as speed

of the sound

S waves:-Secondary waves-Shear waves-Transverse in nature-Follow the P waves in

straight line-Only travel throuhg

solids.-They travel half speed

of P waves

Efects of the EarthquekeWhen the earthquake is produce inside an

ocean or a sea is called Tsunami and beacaus the shaking big waves are produced.

Because of the greats shakings of earthquakes ground ruptures are produced.

They can produces avalanches because of the shaking snow, rocks, etc that are at the top or in a ramp fall down.

Seismic risk areasIf lot of earthquakes are produced in an area

in few time it is a seismic risk area. Most of the risk areas are found in plate

boundaries.Some risk areas are California, Alaska, italy,

Greece, Turkey, some parts of the centre of Asia, New Zaland and Japan.