On the determination of a global strain rate model

The objective of this paper is to outline the fundamental concepts underlyi ng the estimation of a global strain rate model. We use a variant of the me thod first introduced by Haines and Holt (1993) to estimate the strain rate tensor field within all of the Earth's deforming regions, Currently the ob servables used are similar to 1650 geodetic velocities, seismic moment tens ors from the Harvard CMT catalog, and Quaternary fault slip rate data. A mo del strain rate field and velocity field are obtained in a least-squares fi t to both the geodetic velocities and the observed strain rates inferred fr om fault slip rates. Seismic moment tensors are used to provide a priori co nstraints on the style and direction (not magnitude) of the model strain ra te field for regions where no fault slip rate data are available. The model will soon be expanded to include spreading rates, ocean transform azimuths , and more fault slip rate data. We present a first estimate of the second invariant of the global model strain rate field. We also present Euler pole s obtained by fitting geodetic vectors located on defined rigid plates. We find that 17% of the total model moment rate is accommodated in zones of (d iffuse) continental deformation.