Similarities and differences between natural and simulated slow earthquakes

Earthquakes are understood as frictional instabilities taking place in weak zones of the Earth crust called faults. On the one hand, the lengthy recurrence time of earthquakes makes numerical simulations an invaluable tool to study consecutive ruptures of a given fault. On the other hand, it makes a direct comparison with nature difficult, if not currently impossible. Slow earthquakes, exhibiting lower recurrence times, serve as a viable alternative for validating models against real-world observations. We investigate similarities and differences between natural and simulated slow earthquakes using nonlinear dynamical system tools. We focus on slow earthquakes derived from Global Navigation Satellite System (GNSS) position time series in Cascadia and numerical simulations intended to reproduce their pulse-like nature and scaling laws. We provide metrics to evaluate the accuracy of simulations in mimicking slow earthquake dynamics, and we investigate the influence of spatio-temporal coarsening as well as observational noise. Findings indicate that numerical simulations exhibit average properties akin to natural occurrences. In addition, despite the usage of many degrees of freedom in numerical simulations, we retrieve a low average dimension, like the one obtained for Cascadia slow earthquakes, suggesting that a reduced order model may be a viable representation of slow slip events. Time-dependent, instantaneous properties show strong dependence on the variable considered for the analysis for numerical simulations, but not for natural observations. Our exploration show a possible way to extract dynamic attributes from kinematic information, and enriches the picture that we have of natural-scale friction We propose to use the suggested metrics as an additional tool to narrow the divergence between slow earthquake observations and dynamical simulations.