Earthquakes stop when there is not enough energy to keep them going. The energy released by the sliding fault needs to be substantial enough to break the friction holding rocks in place. In some cases, rather than slipping, the two sides along a fault rub together, which can cause a destructive, high-speed quake.
Although the Richter scale has no upper limit, the most devastating earthquakes it measures have magnitudes of 8.0 or higher. More moderate quakes register at 4.5 or greater in magnitude, whereas those of 2.0 or less are typically referred to as "microearthquakes," according to the U.S. Geological Survey. American seismologist Charles Richter (1900 to 1985) developed the eponymous scale in 1935 to quantify earthquake magnitude, or strength.
—From David Biello in Shanghai and wire reports