The great majority of earthquakes that occur each year around the world have natural causes. A small number of lesser-magnitude seismic events have been related to human activities and are called "induced seismic events" or "induced earthquakes" (NRC, 2012). Of concern are induced events that are large enough to be noticed by the public, typically events larger than magnitude 3 (note the range earthquake sizes that are felt can widely vary depending on project location and site characteristics). Induced seismic activity has been described since at least the 1920s and attributed to various human activities including the impoundment of water reservoirs, controlled explosions related to mining and construction, underground nuclear tests, and energy technology developments that involve injection or withdrawal of fluids from the subsurface. Historically known induced seismicity has generally been small in both magnitude and intensity of ground shaking.