Seismic moment

The seismic moment is - like seismic energy or magnitude - a measure of the strength of an earthquake . ${\displaystyle M_{0}}$

It is calculated from

${\displaystyle M_{0}=\mu Au}$,

in which

• ${\displaystyle \mu }$the shear modulus of the rock along the fracture surface (usually 30 gigapascals)
• ${\displaystyle A}$ the area of ​​the fracture surface
• ${\displaystyle u}$ is the average displacement along the fracture surface A.

For historical earthquakes, the seismic moment can be calculated from geological estimates of the fracture surface and the displacement; for today's earthquakes, estimated values ​​are calculated from the seismograms within a short time .

The seismic moment is the basis of the moment magnitude scale , the measure commonly used in seismology today for the strength of an earthquake.