What is the areas under the earth where earthquake waves bounce off?

The areas under the Earth where earthquake waves bounce off are known as seismic wave reflection zones. These zones occur at boundaries between different geological layers, such as the crust and mantle or between different rock types. When seismic waves encounter these boundaries, some waves reflect back, while others may refract or transmit through the layers. This behavior helps seismologists understand the Earth's internal structure and the properties of various geological formations.