Some residents of Reno, Nevada, are leaving their homes after two months of scattered earthquakes. An earthquake that registered 4.7 on the Richter Scale hit Friday night - the strongest in a string of shakes that started way back at the end of February. But that wasn't all: More than 150 aftershocks rumbled through the region over the weekend.

An earthquake is a sudden release of stress that has built up along a fault line, where rock faces push against each other. If that stress could be released over a longer period of time—with a series of smaller quakes—the result might be less catastrophic.

Engineers have known for 40 years that injecting fluids deep into wells can accidentally trigger mini—quakes by lubricating “sticky” rock faces. Since that time, there have been numerous proposals to pump fluids into stressed fault lines.

We know this much: Earthquakes strike along faults—fractures in the planet’s crust where plates of rock are thrust into a sort of geological gridlock. The difference between a tremor and an earth-shattering 8.0-plus-magnitude quake depends on whether the plates slip when the tension between them is still relatively low or if they snap after enduring millennia of mounting strain.

Calculating exactly when this might happen, however, is no easy feat.

Humans are fleeting visitors on this roiling rock in the universe. On December 26, 2004, at 58 minutes and 49 seconds past midnight GMT, Mother Earth reacquainted us with this immutable fact. For millions of years, a creeping slab of Earth´s crust—the India Plate—had been grinding headlong into a similarly stubborn chunk of rock called the Burma Plate. Like a clash of Brobdingnagian armies, millennia of pent-up kinetic energy suddenly exploded from the seabed, a scant 100 miles from Sumatra, Indonesia.