Body wave magnitude () is a way of determining the size of an
earthquake, using the amplitude of the initial
P-wave to calculate the magnitude. The P-wave is a type of body wave that is capable of traveling through the earth at a velocity of around 5 to 8 km/s, and is the first
wave from an earthquake to reach a
seismometer. Because of this, calculating the body wave magnitude can be the quickest method of determining the size of an earthquake that is of a large distance from the seismometer.
Limitations in the calculation method mean that body wave magnitude saturates at around 6-6.5 , with the figure staying the same even when the
moment magnitude may be higher.