What process is it called when a seismic wave crosses a boundary?

When a seismic wave crosses a boundary between different materials, the process is called "refraction." This occurs because the wave changes speed as it enters the new medium, leading to a change in its direction. Additionally, if the wave is partially reflected back at the boundary, this is known as "reflection." Both processes are essential in understanding seismic activity and are utilized in methods like seismic imaging and exploration.