What Is Seismology??

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What Is Seismology??

The study of earthquakes and the structure of the earth, by both naturally and artificially generated seismic waves. An earthquake is defined as the vibration of the Earth’s surface by sound or shock waves usually generated by the energy released from rocks rupturing under stress or by friction between moving rock materials at or mostly below Earth’s surface. A seismologist is a scientist who studies earthquakes and seismic waves.

CHAPTER 1 - What Are Seismic Waves?

Seismic waves are the waves of energy caused by the sudden breaking of rock within the earth or an explosion. They are the energy that travels through the earth and is recorded on seismographs.

How Are Seismic Waves Recorded?

A seismometer records the vibrations from earthquakes. Mechanical versions work by way of a large mass, freely suspended.

In the example on the left, a rotating drum records a red line on a sheet of paper. If the earth moves (in this case from left to right) the whole machine will vibrate too. However, the large mass tends to stay still, so the drum shakes beneath the pen, recording a squiggle! The confiner prevents the mass from bouncing around all over the place.

What Are The Different Types Of Seismic Waves?

There are several different kinds of seismic waves, and they all move in different ways. The two main types of waves are body waves and surface waves. Body waves can travel through the earth's inner layers, but surface waves can only move along the surface of the planet like ripples on water. Earthquakes radiate seismic energy as both body and surface waves.

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Wave Type 1: Body Waves

P Waves

The first kind of body wave is the P wave or primary wave. This is the fastest kind of seismic wave. The P wave can move through solid rock and fluids, like water or the liquid layers of the earth. It pushes and pulls the rock it moves through just like sound waves push and pull the air.


The arrow shows the direction that the wave is moving.

S Waves

The second type of body wave is the S wave or secondary wave, which is the second wave you feel in an earthquake. ...

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