Here's how it works:
1. Sound waves are sent into the ground: A seismic source (like a truck vibrating the ground or explosives) generates sound waves that travel into the Earth.
2. Waves reflect at different densities: As the waves travel, they encounter different rock layers with varying densities. When a wave encounters a change in density, part of the wave is reflected back to the surface.
3. Reflections are recorded: Geophones (sensors placed on the surface) detect these reflected sound waves and record the time it took for them to return.
4. Data is processed and interpreted: The recorded data is then processed and interpreted to create a visual representation of the subsurface, much like an X-ray. Different reflection patterns indicate different rock types and structures, revealing features like faults, folds, and the presence of oil or gas reservoirs.
Key takeaway: Seismic reflection is a powerful tool for understanding subsurface structures because it leverages the fact that rocks with different densities reflect sound waves differently.
