NEXTQUAKE: a MATLAB tool to transform an active fault database into seismic hazard input

Seismic hazard models increasingly rely on detailed active fault databases to explicitly represent earthquake sources and their complex geometries. However, transforming fault-based information into consistent and physically plausible inputs for probabilistic seismic hazard analysis (PSHA) remains a non-trivial and often fragmented task. We present NEXTQUAKE, a modular MATLAB tool designed to bridge this gap by converting an active fault database into a complete, internally consistent seismic hazard input. The first core component of NEXTQUAKE generates a comprehensive catalog of earthquake ruptures starting from the geometry of an active fault system. The algorithm constructs single-fault and multi-fault ruptures while enforcing physical plausibility through a fault-to-fault and subsection-to-subsection connectivity framework. Multi-fault ruptures are generated only among geometrically and kinematically connected faults, dramatically reducing the combinatorial space and ensuring realistic rupture scenarios. Each rupture is described in terms of geometry, area, and magnitude, and is encoded through a sparse subsection–rupture incidence matrix that enables efficient downstream processing. The second component performs an inversion to estimate the expected occurrence rates of all generated ruptures. The inversion integrates geological and geophysical constraints, such as long-term slip rates, and provides a self-consistent set of rupture rates compatible with the fault database. This step allows the direct use of fault-based information within probabilistic frameworks without relying on simplified or ad hoc assumptions. Finally, the third component of NEXTQUAKE translates the rupture catalog and associated rates into fully compliant input files for OpenQuake, enabling seamless integration with state-of-the-art PSHA engines. By automating the entire workflow, NEXTQUAKE offers a transparent, reproducible, and extensible framework for fault-based seismic hazard modeling. NEXTQUAKE is particularly suited for regional-scale applications and for exploring the impact of rupture connectivity assumptions on seismic hazard results.