Accelerometers are instruments that measure accelerations. Acceleration can be static as the earth's gravity pulling objects toward the earth, or dynamic as caused by oscillatory movements of the instrument.

NEPTUNE broadband Ocean Bottom Seismometers (OBS) include three components, with accelerometers as strong motion add-ons. The seismometer sensors (velocity) are more sensitive than the strong motion accelerometers, but ground shaking caused by strong local earthquakes exceeds their measurement range.