Generally, the size of an earthquake is called its magnitude.
Earthquake’s magnitude is defined as the measure of the amplitude of the seismic waves. A seismometer or seismographs are used to measure seismic waves. So, the statement describes one aspect of an earthquake’s magnitude is that Earthquake’s magnitude depends on the size of seismic waves.
Earthquake’s magnitude is measured by the Richter magnitude scale.
Hence, the correct answer is It is based on the size of seismic waves.
