Moment Magnitude Scale Mw
The moment magnitude scale has become the more commonly used method for determining
the magnitude of large earthquakes. This is because it tends to take into account the
entire size of the earthquake. The first step in the calculation of the moment magnitude is
to calculate the seismic moment M0. The seismic moment can be determined from a seismogram
using very long-period waves for which even a fault with a very large rupture area
appears as a point source (Yeats et al. 1997). The seismic moment can also be estimated
from the fault displacement as follows (Idriss 1985):