Seismic moment that accumulates on locked faults during the interseismic period must be released in large seismic events. Measurements of surface velocity from GPS and InSAR can be inverted for locked patches but the inverse problem has the same non-uniqueness and instability as gravity inversion. In this talk we show that moment accumulation rate can be measured from surface velocity without inversion. The accuracy of this measurement relies on the accuracy and spatial coverage of GPS and InSAR data. For example, space geodetic data suggest that significant moment is accumulating along the Creeping Section of the San Andreas Fault but the InSAR measurements must be improved to reduce the uncertainty. This will happen over the next 2 years with data being collected three new InSAR satellites ALOS-2, Sentinel-1A, and Sentinel-1B.