Probabilistic tsunami hazard assessment and flood modeling: a case study of Manzanillo, Colima, Mexico

This study presents a site-specific seismic-source probabilistic tsunami hazard assessment for Manzanillo, Colima, a coastal city in Mexico vulnerable to local tsunamis due to its proximity to the subduction zone along the Mesoamerican Trench. Historical records show that the region has been affected by significant tsunamis, most notably in 1932 and 1995. Using stochastic earthquake source models and numerical simulations, we calculated tsunami inundation scenarios for different return periods (50, 100, and 500 years). The study employs the GeoClaw open-source software package, incorporating high-resolution topography and bathymetry, to simulate tsunami wave propagation and coastal inundation. Model validation using the 1995 Colima-Jalisco event demonstrates that the simulation correctly captures the observed tsunami characteristics. The results reveal that lowland areas, particularly near Manzanillo and Santiago Bays, and the Cuyutlán Lagoon, could experience inundation of several kilometers inland in a worst-case scenario. Exceedance probability curves indicate a high likelihood of moderate to significant tsunami wave heights within a 500-year time frame, underscoring the substantial hazard to the city. The main academic contribution of this study is the integration of stochastic seismic-source hazard modeling with local hydrodynamic inundation simulations, together with an explicit comparison between simplified elevation-based mapping and physics-based inundation modeling for a lagoon-influenced urban coast. The results also provide information relevant for hazard mapping and preparedness in Manzanillo. Manzanillo is a city on Mexico’s Pacific coast prone to tsunami events as it lies near a major seismic zone. In this study, we estimated how often tsunamis might flood the city and how far the water could go inland by using computer models to simulate many possible earthquakes on the ocean floor and the tsunamis those earthquakes would generate. To check that the models work, we first simulated the known tsunami from 1995 and found that the results matched the observations of the event. With this validated model we created maps showing which parts of Manzanillo would flood for events that might happen once in 50, 100, or 500 years. The maps show that areas near the coast and lagoons are the most exposed, and in the worst cases, water could travel a few kilometers inland. This information is very important for people in Manzanillo, as it can improve city planning, for example, by deciding where it’s safe to build, creating evacuation routes, and making sure everyone knows what to do if a tsunami is coming. By preparing now using these scientific results, Manzanillo can be safer in the future when a tsunami occurs. A Probabilistic Tsunami Hazard Assessment (PTHA) was conducted for Manzanillo, Mexico. Model validation aligns well with 1995 Colima-Jalisco tsunami observations. Santiago Bay, Manzanillo Bay, and Cuyutlán Lagoon face the highest inundation hazard. Findings support enhanced tsunami mitigation, zoning, and evacuation planning.