Special Notice: ENERGY, DEPARTMENT OF is seeking Open Source Software: MASTODON for pioneering multi-hazard analysis for critical infrastructure. MASTODON is a cutting-edge software tool that offers a comprehensive solution for modeling stochastic nonlinear soil-structure interactions (NLSSI), bringing a new level of sophistication to dynamic probabilistic risk assessments. It is designed to simulate how structures like nuclear facilities, dams, and bridges respond to external hazards, including seismic events. MASTODON excels in the numerical modeling of seismic soil-structure interaction and sets a new benchmark in risk assessment tools. It offers advanced NLSSI modeling, enables precise risk analysis for critical infrastructure against multiple hazards, simulates the entire process from earthquake fault rupture to structural response with high fidelity, enhances the reliability of risk assessments by accurately quantifying uncertainties, and leverages the MOOSE framework for computational efficiency and flexibility. MASTODON is applicable to nuclear facilities, critical infrastructure, and facilitates dynamic probabilistic risk assessments for various external threats. Visit the GitHub page to learn more and download the software for evaluation.