# data[].attributes.attachment_link.description
Although it makes a fascinating story, it is not possible to journey to the center of Earth. Instead, scientists gather observations at the surface to construct models of Earth's internal structure. They analyze seismic data-information from earthquakes-to infer processes that occur inside the planet.

# data[].attributes.attachment_link.description
When an earthquake occurs, seismic waves travel through the planet. Every earthquake generates two types of waves-primary, or P waves, and secondary, or S waves. A worldwide network of seismometers, instruments that track earthquakes, records the arrival of P and S waves from all over the globe.