The surface wave magnitude scale has an advantage over the local magnitude scale in
that it uses the maximum ground displacement, rather than the maximum trace amplitude
from a standard Wood-Anderson seismograph. Thus any type of seismograph can be used
to obtain the surface wave magnitude. This magnitude scale is typically used for moderate
to large earthquakes, having a shallow focal depth, and the seismograph should be at least
1000 km (622 mi) from the epicenter.