INTERPRETING INTERSEISMIC OBSERVATIONS WITH MICROPLATE MOTION MODELS

A key step in assessing earthquakes hazard is the estimation of slip rates on seismically active faults. Space geodetic observations of interseismic behavior provide constraints for doing so by way of a plate tectonic framework called block modeling. Block models can be used to interpret interseismic geodetic surface velocity fields as comprising 1) rotation of tectonic microplates, 2) elastic strain accumulation about partially to fully coupled faults that bound the microplates, and 3) homogeneous deformation within microplates. Fault slip rates derived from a block model are kinematically consistent, as they are calculated directly from the estimated microplate rotations; inherently reflect the effects of mechanical interactions with neighboring structures; and can be compared to long-term slip rates inferred from geologic data. Recent applications of block modeling include 1) assessing the partitioning of relative plate motion between subduction zones and crustal faults in Japan, 2) estimating the relative magnitudes of deformation accommodated by major faults and more diffuse processes in the Tibetan Plateau, and 3) calculation of interseismic stressing rates on the San Andreas fault.