The movement of sudden tectonic plates causes seismic activity underground.and seismic activity often happen with sudden movements underground with tectonic plates.
Seismographs are used by scientists to measure the time, location and strength of an earthquake. Magnitude illustrates the strength of an earthquake, according to AccuWeather. Following an earthquake, several seismic stations submit their readings to reach a consensus about the quake. The readings are communicated in terms of magnitude, and the intensity, based on the effects on people and structures, is communicated with the Modified Mercalli Intensity Scale.: These tend to be I-V on the MM scale. Anything in this intensity range does not generally cause considerable damage. On the higher end, shaking may be felt by many, and windows and dishes may break.