Final answer:
Late and early arrival times for P-waves are explained by the varying densities of subsurface materials, as the velocity of P-waves changes with material density, affecting their travel path and arrival times.
Step-by-step explanation:
Late and early arrival times for P-waves can be explained by varying densities of subsurface materials. This occurs because the velocity at which P-waves travel changes based on the density of the materials they pass through, affecting their travel path. Seismic waves like P-waves are reflected and refracted, indicating the Earth's internal structure is not homogeneous. The speed of P-waves ranges from 4 to 7 km/s in various materials and is faster in more rigid ones like granite.
Understanding the differences in wave characteristics, including their speed, reflection, and refraction properties, is crucial to interpreting seismic data. This differentiation helps to pinpoint the epicenter of earthquakes and to study the composition and state of Earth's internal layers.