Seismic waves

powerpoint presentation

1. Seismic Waves

2. Seismology is a branch of geophysics which concerned with study of earthquakes and transmission and dissemination of seismic waves within the Earth. Seismic waves are vibrations that are usually generated by earthquakes or explosions and are propagated within the Earth or along its surface.

3. A seismograph records varying magnitude of ground oscillations caused by seismic waves that travel from their point of origin through the Earth or along its surface . Magnitude is the measure of the energy released at the source of the earthquake and it is expressed using the Richter scale. In 1935, Charles F. Richter of the California Institute of Technology developed a mathematical device to measure and compare the magnitude of earthquakes.

4. Types of Seismic Waves Body Waves – it travel through the Earth’s mantle and crust. 1 . primary waves (also called P waves) – are the fastest of all the seismic wave types and produce longitudinal movement (in the same direction of the wave propagation ). 2. S wave or secondary waves (also called shear waves) – moves through the body of the earth but are slightly slower than P waves and produced perpendicular wave motion, unlike P waves, cannot travel through liquid. -

5. Surface Waves 1. Love Waves (1911, Augustus Edward Hough Love) – Move the ground from side to side in a horizontal plane but at right angles to the direction of propagation. The horizontal shaking of Love waves is damaging to the foundations of structures. 2. Rayleigh Waves (1885, Lord Rayleigh) – this wave moves like rolling ocean waves. In addition it moves both vertically and horizontally in a vertical pane pointed in the direction in which the waves are travelling.