How do seismic waves make an image of Earths interior?
Imagine you are a geoscientist who studies active volcanoes. You want to know if the magma chamber of a particular volcano is near the surface, suggesting an eruption in the near future. Or, you are a seismologist who needs to understand the earthquake potential in Southern California and so wants a subsurface map of the faults in the region. Seismic imaging offers the ability to “see” structures that are deeper than we can otherwise study. The process of making three-dimensional images of Earth’s interior using seismic signals, called seismic tomography, can be likened to the three-dimensional imagery of a CAT scan. A CAT scan (Computed Axial Tomography) generates a three-dimensional image of the brain by stacking a lot of flat, two-dimensional X-ray pictures. The basic idea of a CAT scan is this: the X-ray beam moves all around the patient, taking images from hundreds of different angles. A computer takes the information and puts together a three-dimensional image of your inner soft
