SUMMARY

GPS studies of Guerrero, southern Mexico, have described large slow slip events on the Cocos-North American plate boundary in 1996, 1998 and 2002. In this study, we show that five smaller events occurred in 1999, 2000, 2001, 2003 and 2004. These eight events are quasi-periodic with a period of 12.00.3 months, similar to periodic slow slip else-where but with more variable moment release. Perhaps the most important application of GPS data is to seismic hazard, but transient slip complicates estimation of the to-tal strain moment available for seismic release. To examine seismic hazard in Guerrero, we model the slip deficit using two end-member representations of slow slip: (1) a single rectangular patch on the plate boundary, and (2) a 20-km-mesh discretization. The models yield very different estimates of slip location and moment release, but both models locate slow slip near the base of the seismogenic zone, and both require negligible slip during inter-event periods to surprising depth on the plate boundary. The discretized model con-2 A. R. Lowry et al. firms that slow slip can be driven by potential energy accumulated as slip deficit between events. Residual slip deficit accumulated during the 1992–2005 period of GPS observa