Question

Hoe do earth quake help us knowning about intrnal earth structure

Answer 1

It is impossible to drill to the center of the earth, so scientists rely on indirect observations of matter lying below the surface through use of seismic waves and their knowledge of how these waves travel during and after an earthquake. The speed of seismic waves is affected by the properties of the material the waves pass through; the stiffness of material affects the speed of these waves. Measuring the time it takes for certain waves to get to a seismometer after an earthquake can indicate specific properties of the materials that the waves encountered. Where a wave encounters a layer with a different composition, it will change direction and/or velocity. There are two types of seismic waves: P-waves, or pressure waves, which go through both liquids and solids, and S-waves, or shear waves which go through solids but not liquids. P waves are the faster of the two, and the gap between them provides an estimate of the distance to the earthquake. Seismic studies from 1906 indicate that the outer core is liquid and the inner core is solid.