Characterization of Seismicity Rates on the Megathrust and Sliver Fault in Southern Mexico with Potential Relationships to Aseismic Slip

The Mexican subduction zone is considered a natural laboratory for studying slip processes due to the relatively short (∼50 km) trench-to-coast distance which brings broad portions of the seismogenic and transition zones ∼250 km inland. Slow slip events (SSEs) have been identified to occur downdip of the megathrust seismogenic zone where the friction style changes from stick-slip to stable sliding. A recent study by Fasola et al. (2019) found that correlated SSEs and seismicity in the Oaxaca Region also occurred on a crustal sliver fault that accommodates the partitioning of oblique convergence in Mexico. Thus this region provides an opportunity to pursue a detailed characterization of potential relationships between the seismicity and aseismic slip on a complex fault plate boundary system. In this study, we investigate temporal variations in seismicity rates using template matching strategies to enhance seismic sequences cataloged over the years 2006-2022. Specifically, we use waveform correlation primarily focused on earthquake swarms to enhance the detection of smaller magnitude sequences not identified by the original catalog. This allows us to improve the detection of fluctuations in seismicity rates and their potential relationships to processes identified in geodetic data such as SSE or variations in interseismic coupling. Overall, this study not only aims to estimate variations in fault behavior during the earthquake cycle but also characterize the seismic hazards presented by SSEs and quantify how these hazards have varied through time in the Mexican subduction zone.