Coseismal is a rare term used to describe an earthquake that is felt only by a small number of people in a confined area and is not registered on seismographs. There are a few synonyms that can be used instead of coseismal, such as microseismic, which refers to any earthquake that measures less than 2.0 on the Richter scale. Another synonym is tectonic tremor, which describes a low-frequency seismic event that is caused by movement along fault zones. Additionally, foreshocks and aftershocks can be used to describe smaller earthquakes that occur before and after a larger, more significant earthquake.