Induced seismicity caused by hydraulic fracturing are small earthquakes that typically happen deep underground where the rock is being fractured. In rare instances, seismic events create anomalous vibrations that are felt on the surface. These are called anomalous induced seismicity or “felt events.” The vast majority of induced seismicity caused by hydraulic fracturing result in magnitudes of less than 1 ML as measured on the Richter scale and are not felt.