The first-order statistical moment of the seismic moment tensor

Summary. If a complex earthquake is assumed to be a set of individual, randomly oriented elementary pure double couple sources, the solution for the seismic moment of the complex event projected on the mean trend of the fault will perforce be comprised of sources of both double couple and compensated linear vector dipole (CLVD) types. We investigate the statistical properties of these two components of seismic sources in terms of the invariants of the seismic moment tensor of a realistic set of synthetic earthquakes. It is very likely that the size of the CLVD component is two to three orders of magnitude smaller than that of the double couple component.