Exploring Seismology

Exploring 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?

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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

seismometer with suspended mass, spring, confiner and rotating drum of paperRecorded?

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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?

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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.

Wave Type 1: Body Waves

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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.