Time-dependent inversion of three-component continuous GPS for steady and transient sources in northern Cascadia

An approach to invert GPS time series to estimate crustal block rotations, fault locking and strain rates while simultaneously solving for transient slow slip events is described and applied to the northern Cascadia subduction zone. The method can use continuous or survey mode GPS time series or both. I invert 5.6 years of 3-component continuous GPS time series at 53 sites from Cascadia to estimate simultaneously the block motions and strains, locking on the subduction zone and source parameters of the four most recent slow-slip events. Over the time period and section of the Cascadia margin sampled, the strain released in slow slip was 7 to 10% of the accumulated subduction strain but at the base of and immediately downdip of the locked zone beneath the Olympic Peninsula.