Analyzing slip events along the Cascadia margin using an improved subdaily GPS analysis strategy

A GPS analysis strategy that reduces the noise level of GPS-based subdaily strain measurements and improves subdaily resolution of positions enables the use of baseline estimates in the study of slow slip events along the northern Cascadia margin. We first evaluate this strategy's performance through comparisons of strain estimates at co-located GPS stations and borehole strainmetres, and then examine the strain migration during the 2008 May episodic tremor and slip (ETS) event. The temporal evolution of the ETS event is extracted from the GPS baseline analysis of the bidirectional propagation of the 2008 May event. These results establish the strain estimates from subdaily GPS baseline measurements as a reliable technique that can be used for mapping regional strain variations during episodic slip in regions where no laser or borehole strainmetres exist and GPS stations are abundant.