How has seismic waves been used to determined earths structure and composition?

Seismic waves, generated by earthquakes or artificial sources, travel through the Earth's interior and are analyzed to infer its structure and composition. By studying the speed and behavior of these waves, scientists can identify different layers of the Earth, such as the crust, mantle, and core, as well as their physical properties. For instance, the difference in wave velocities indicates transitions between solid and liquid materials, revealing that the outer core is liquid while the inner core is solid. This method has provided critical insights into the Earth's composition and the dynamics of its interior.