Large earthquakes, like the recent M7.8 in Alaska, can be seen at seismometers around the world! When an earthquake occurs, seismic energy travels in all directions, much like ripples in a pond. The globes at the top illustrate this (yellow star = the earthquake, red triangle = seismic station). The colored lines represent different paths seismic energy takes through the earth, and how the energy interacts with the earth’s layers (represented by gray circles). From this, it’s easy to see how earthquakes provide the best tools for understanding the earth’s internal structure!