How do seismic wave data reveal the internal structure of the Earth?
Earthquake Shadow Zones: Extensive study of shock waves of earthquakes and the global monitoring of underground nuclear bomb testing reveal information about the internal structure of the Earth. P and S waves both go through solids. S waves do not go through non-solids, so only P waves are received on the opposite side of the Earth. Zones of seismic wave shadows occur in the regions shown in Figure 1.17 between about 105° to 140° on the opposite side of the globe from a seismic shock. These shadow zones shows us that part of the Earth's core is liquid material (molten material). In contrast, the inner core is believed to consist of solid metal, possibly similar in composition of iron meteorites.
What can seismic (P and S) waves data tell us?
• Parts of the earth are not solid.
• The depth and location of an earthquake.
• The relative strength of an earthquake.
• The average density of Earth.
• The density of each layer in the Earth.