Geodetic Observations and Modeling of the 2010 Episodic Tremor and Slow Slip Event in the Cascadia Subduction Zone
Abstract
The Cascadia Subduction Zone (CSZ) is capable of producing large megathrust earthquakes and frequent slow slip events (SSE) accompanied by non-volcanic seismic tremor. This phenomenon is referred to as Episodic Tremor and Slow Slip (ETS). This thesis investigates the spatial and temporal relationship between tremor activity and GPS- inferred fault slip during SSE, focusing on the 2010 event. Static and time-dependent GPS data from the PANGA network, as well as tremor data from the Pacific Northwest Seismic Network (PNSN), are analyzed. Slip distributions are modeled using the Okada (1992) model, and tremor-derived slip is calculated using the seismic moment scaling from Aguiar et al. (2009). Results show that tremor- derived slip can reproduce surface deformation patterns observed by GPS with high consistency, with the total seismic moment differing by 18.5%. While GPS data yield a smoother displacement field, tremor-based modeling reveals more detailed and heterogeneous slip distributions, possibly capturing finer fault dynamics. Small differences in slip vector direction and magnitude may be attributed to data noise and methodological limitations, such as fitting offsets in noisy GPS signals. This work highlights the importance of combining geodetic and seismic observations to better understand subduction processes and improve earthquake hazard assessment in the CSZ.