The fundamentals of earthquake mechanics are simple: Pieces of rock slip past one another along a fault to release pent-up energy. Some of that energy ripples outward, causing seismic waves that shake the earth. But how long it takes and exactly how the energy dissipates has remained elusive. To discern these processes, researchers recently built a machine at the University of Oklahoma to mimic what happens inside the earth's crust.
This oozy, pockmarked image is the surface of Jupiter’s moon Io, from the first complete geologic map of the turbulent orb. Io is the most volcanically active place in the solar system, so it’s of great interest to geologists because its surface is continually refreshing and renewing. It’s the only celestial body where scientists have not seen any impact craters.