Why is it useful to record seismic waves with a seismograph?

Answer 1

Three different types of waves travel away from the focus of a seismic event. These waves travel at different speeds. In addition to surface waves, the waves that are proving critical to providing evidence about the interior of the Earth are 'P' waves (P standing for primary or pressure), and 'S' waves (S for secondary or shear). P-waves are faster than S-waves.

P-waves can travel through solid rock and fluids, and their speed will vary depending on the density of the rock through which they travel; increased speed will indicate increased density, thus providing information about the density and possible mineralogy of Earth's various layers.

S-waves cannot travel through fluids, thus when an S-wave encounters the outer core of the Earth (liquid iron and nickel), it is disrupted, indicating the boundary between the mantle and outer core and the boundary between the inner core and outer core. The effect observed from the motion of S-waves reveals a 'shadow zone', opposite to where they originate.

An animation of P and S-waves moving through Earth's interior and the resultant S-wave shadow due to the presence of the Earth's core is viewable in the related links section.
Geologists use seismic waves to learn about the earth's interior by using the reflection or refraction of the seismic wave to investigate subsurface structures and locate the epicenter.

Answer 2

We study seismic waves to learn about Earth's interior. Humans can't dig down to Earth's core and help from seismic waves has helped us find out the layers of Earth and how thick they are, and what they consist of.

Answer 3

they are useful because they give off a signal which is picked up in different parts of the world which are called Eco systems. seismic waves can be measured to determine how extreme or how threatening and earthquake is. before the earthquake starts signals are let of to the Eco systems as a warning so the area can be evacuated. but if the Eco system is in the middle of the ocean they cannot be detected therefore no warning is given to the civilization where the earthquake is going to happen and no-one is evacuated so more people die.

Answer 4

If there was one of them that had no interest in seismic waves, and was bored

by the whole subject, then he would no longer have the right to call himelf a

seismologist. He would instantly lose the reputation and respect carried by

that label, and all his friends would soon discover that he's just a regular guy.

Answer 5

they are used to see how big each section of earths interior

Answer 6

It is useful because you can find out how far the earthquake is and how much vibrations you can fell at where you are at

Answer 7

They are helpful because they help measure movements in the ground that no one can feel.