Clustering of major earthquakes over periods of years to decades is observed historically and in paleoseismic records. Seismic hazard forecasts may be improved by identifying a cluster in-progress and its relationship to fault loading processes. I present new long-term fault slip-rates from the Eastern California shear zone (ECSZ), where both paleoseismic and historic earthquake clusters are recognized, to test if the interseismic loading rate is transiently elevated during the present cluster of activity. The sum of six fault slip rates that average a few to several tens of earthquakes is 5.2±1.9 mm/yr. This long-term rate is only half the present-day loading rate of 12±2 mm/yr across the 60 km-wide shear-zone. This discrepancy began prior to the 1992 Mw 7.3 Landers earthquake, and its magnitude precludes residual post-seismic deformation following other large historic earthquakes in southern California. These observations support that significantly elevated regional strain accumulation rate may be characteristic of clustered earthquake activity, and that interseismic loading may oscillate between different fault sets within a hierarchal fault system.