Improving resolution model of probable asperity distribution along southern Sumatra Subduction Zone using denser GPS stations

The southern Sumatra Subduction Zone (SSZ) is point outed as an area with seismic potential due to plate tectonic movement. To observe seismic activity in this region, Global Positioning System (GPS) networks can be used to monitor tectonic plate movement. We aim to determine the best resolution model of probable asperity zone in the southern SSZ by testing various slip patch models and using the GPS networks (SuGAr, InaCORS, SuMO, and UNIB networks) installed as synthetic data. This study provides a necessary resolution analysis and a validated methodology, providing a reliable foundation for future studies of interplate coupling models, interseismic deformation, and seismic potential. The testing of resolution model was conducted using a Checkerboard Resolution Test (CRT) through Akaike Bayesian Information Criterion (ABIC) inversion and a bicubic b-spline basis function to parametrize the slip velocity. The results show that utilizing a denser GPS station network by adding the SuMo and UNIB networks (47 stations) can improve resolution model from 40-70% to 80-100% in southern Sumatra near land areas. This enhancement confirms that the denser station distribution is crucial for resolving fine-scale slip heterogeneity. Consequently, the Bengkulu-Enggano segment can now be modeled with high fidelity, providing a reliable foundation for future studies of interplate coupling models, interseismic deformation, and seismic potential. • Denser GPS networks boost resolution from 40-70% to 80-100%. • Network density is key to resolving fine-scale fault asperities. • Land-based data has a critical blind spot offshore near the trench. • Seafloor geodetic stations crucial for resolving offshore seismic gaps. • Optimal 16-km spline interval ensures stable asperity modeling.