It is not clear over what depths locked and creeping portions of the Hayward fault extend, leading to substantial uncertainty about potential earthquake magnitudes and probabilities. Measurements of surface displacements surrounding a fault using GPS or terrestrial surveys can be used to compute models of the distribution of slip on a fault system. However, most precisely surveyed points near the Hayward fault are spaced more than 10 km apart and it is therefore difficult to determine a reliable slip estimate. This technique only provides measurements of one component of the displacement field along the look direction of the radar. Range changes are computed from InSAR interferogram by unwrapping angular phase delays and converting from phase delay to range change.
Good correlation occurs almost exclusively in urban areas.
We can now formally combine the two data sets in our model inversions. Additional GPS data and additional redundant InSAR data are required to better constrain our models. Results Measurements of active deformation along the northern Hayward fault consist of surface creep data at the active fault trace, GPS measurements of benchmark motions, and InSAR measurements of range change differences near the Hayward fault. We assume that the deformation has been steady and integrate creep rates from the last several decades with GPS derived displacements between 1993 and 1998, and InSAR measured range changes between 1992 and 1997. Discrete offsets due to aseismic creep at the surface are apparent along the trace of the actively creeping Hayward fault.