First off, let's look into how an earthquake happens:
As the plate move apart or collide given the convection current of magma, stress is built up with continuous plate movements. The pressure is then greater than the elastic strength of the rock. Rock breaks, the pressure of energy is released in the form of seismic waves. Ground vibrates, resulting in earthquake.
How it provide evidence about the layers of Earth, is that the lower the layer, the hotter it is, which then cause the convection current of magma to happen,hence affecting the lithosphere.
The earthquake is a sudden release of wave energy in the earth and reaches the surface form the weakest points and this is said to be focus of the earthquakes they tend to in the form of the P, S, L waves and they have been studied through the help of the seismograph and the Richter scale, that records the slightest earth movements and thus helps in understanding the surface in the earth at greater depths.
<u>As these waves past through the earth material they bend, turn like the rays of light and this creates shadow zones due to the presence of a discontinuous zone under the earth like the gaps between the upper crust and the lower mantle is called as the Gutenberg discontinuity. </u>
