Source parameters and time-dependent slip distributions of slow slip events on the Cascadia subduction zone from 1998 to 2008

We invert for the time-dependent slip history of slow slip events on the Cascadia subduction zone using GPS data from 1998 to 2008. The 16 slip transients have sufficient station coverage to solve for the slip distribution on the plate interface. GPS time series are inverted for fault slip using the Extended Network Inversion Filter. Limited station coverage south of Portland (45.5 degrees N latitude) restricts our analysis to events on the northern half of the subduction zone. Slip is resolved at the base of the seismogenic zone and the slip distributions suggest a potential segment boundary near Seattle (47.6 degrees N) that correlates roughly with geologic and tectonic boundaries. Events that initiate to the north and south tend to overlap at about this latitude. We compile statistics on source parameters, such as propagation rate, recurrence interval, and stress drop, which can be used to constrain proposed models of the source mechanics. Over a 10 year period, total strain release from slow slip events is nonuniform along strike with the greatest cumulative slip (27 cm) centered beneath Port Angeles (48.1 degrees N). This slip patch also exhibits the most regular recurrence of Mw similar to 6 events relative to other locations along strike. The spatial extent of the slip patch beneath Port Angeles correlates with the along-strike bend of the Cascadia subduction zone in northwestern Washington, suggesting that plate geometry plays an important role in controlling the along-strike characteristics of slow slip.