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The inland inundation of a tsunami is characterized by significant variations in speed. While open-ocean propagation can reach hundreds of kilometers per hour, upon making landfall, this velocity undergoes a substantial reduction. The precise rate of movement across terrestrial surfaces is contingent upon factors such as the bathymetry of the coastline, the slope of the land, the presence of obstructions like vegetation and buildings, and the volume of water involved. For instance, a large tsunami encountering a gently sloping coastal plain will advance more rapidly and farther inland than a smaller wave impacting a steep, rocky shoreline.

Understanding the rate at which a tsunami inundates coastal areas is paramount for effective hazard assessment and mitigation. Accurate velocity estimates allow for improved evacuation planning, informing the public about safe zones and the time available to reach them. Moreover, these data contribute to the refinement of predictive models, enabling more precise forecasts of inundation extent and depth. Historically, underestimation of inland surge speeds has led to inadequate response measures and increased devastation, underscoring the critical need for detailed analysis and modeling of onshore tsunami behavior.

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