Rocks along a fault are held together by friction and can't slide past each other. Plate tectonic motions apply stress to the rock, building strain energy until it's greater than the friction, causing an earthquake. Energy is transmitted as seismic waves
Strain energy
Energy built up in a section of rock under stress that changes its shape and breaks when the stored energy exceeds the rock's strength
Epicentre
The point on the surface above the focus of an earthquake
Focus
Where the earthquake originated from
Elasticity
A property of materials that result in wave propagation and earthquakes
Primary waves
Longitudinal waves
Secondary waves
Transverse waves
Surface waves
Rayleigh waves
Love waves
Inertial mass
Used in the earliest seismometer
waves travel 1.7 times faster than s-waves, followed by love waves and Rayleigh waves
Factors affecting wave speeds
1. Incompressibility: ability of a rock to resist change in volume, affecting wave speed
2. Density: denser materials slow down wave speed
3. Rigidity: resistance to bending, affecting wave speed
Density increases closer to the core of the earth
Wave speed slows down, but incompressibility increases faster than density, resulting in an overall increase in wave speed
