Introduction to Earthquakes

 Woah, WAIT, is that...

EARTHQUAKE!!!

Image: From Tappity

What is an Earthquake? 

An earthquake is a series of shocks, seismic waves or tremors that result from a sudden release of pressure. 

• Focus: Point below the surface where seismic waves radiate from the source/origin 

• Epicentre: The point on the surface immediately above the focus of the earthquake, this is where the most damage can be noted. 

Causes of Earthquake Activity:

• Physically Induced: Tectonic plates moving against each other or where there is volcanic activity

• Human Induced: Mining, drilling to the earth, underground explosions

N.B: These contribute to the inducing of earthquakes as the create shock waves which cause changes (pressure changes) in the rock strata. 

Types of Earthquake Waves: 

Two types of seismic waves can occur, following the event of an earthquake. 

1. Body Waves: Shock waves that are transmitted upwards to the surface from the focus. It can be divided into:

• Primary/Pressure/P Waves: Fastest, moves through solids and liquids 

• Secondary/Shock/S Waves: Moves with a sideways motion, ground moves horizontally and results in great damage, unable to move liquids

When these body waves get to the surface, the may be transformed into surface waves.

2. Surface waves:     Long waves -  sideways (and faster)

                                    Rayleigh waves - up and down