How do seismic waves provide a detailed picture of earth's interior?

The different layers of the earth have different densities, and the seismic waves produced during an earthquake travel at different speeds through these layers. By measuring the different speeds, we can clarify the presence of layers within the earth, as well as their densities. Waves will travel faster through thinner layers, and slower through more dense layers. 

The virus is considered to be are living item since they have hereditary material dnas or rnas. they can imitate and change. they respond to boosts, for example, radiation, chemicals, and warmth. they have antigenic properties. they are proficient to duplicate with a same hereditary constituent.