The earth rumbles beneath us, but it's impossible to predict when and where a quake will strike. That's because quakes are caused by movements, or slips, along existing faults. When these slips happen, energy is pumped into the rocks and causes them to vibrate. This vibration, known as an earthquake, can cause buildings to collapse and injure or kill people.
Seismologists study these vibrations to see if they can spot any signs that an earthquake might be on the way. They look for two types of waves: P waves, which advance quickly and push, pull and compress the ground like a Slinky; and shear or S waves, which move more slowly and can shake the ground side to side or up and down.
Scientists have been able to use this information to predict the time of aftershocks, which are quakes that follow on from a bigger, mainshock quake. They can also churn out equations that give a time window in which a quake is likely to occur, but they can't predict a specific earthquake.
But, as the Nautilus magazine reports, scientists now have a new tool to make a better picture of what's happening under our feet. By analyzing data from sensors that measure the speed of the plates that make up the Earth, scientists can now get a much clearer view of the movement of the rock and what's causing it. The sensors can pick up micro-quakes that wouldn't be obvious to the naked eye or a computer screen, but are still noticeable when you zoom in. They can also find distortions in the motion of a plate, which might indicate where stress and strain are building up.