Date of Award
2026
Degree Type
Dissertation
Degree Name
Doctor of Philosophy in Ocean Engineering
Department
Ocean Engineering
First Advisor
Stephan Grilli
Abstract
Tsunamis represent one of the most destructive natural hazards affecting coastal regions worldwide. Although they are much less often than storms or tides, their ability to generate rapid inundation, strong currents, and extreme forces over large spatial scales makes them particularly hazardous to coastal communities and critical infrastructure. The increasing concentration of population and assets along coastlines, combined with improved observational and numerical modeling capabilities, has underscored the need for comprehensive and physically based tsunami hazard assessments that extend beyond historically impacted regions.
In the United States, tsunami hazard has traditionally been associated primarily with the Pacific Ocean basin, where frequent seismic activity along subduction zones has produced numerous damaging events. In contrast, the U.S. East Coast (USEC) has long been perceived as relatively safe from tsunami impacts due to its lower level of regional seismicity. However, geological evidence, historical records, and recent modeling studies demonstrate that the USEC is vulnerable to tsunamis generated by a range of far-field and near-field sources located throughout the North Atlantic Ocean basin. These sources include large coseismic earthquakes, submarine mass failures, and volcanic flank collapses, each capable of producing tsunamis with potentially damaging coastal impacts.
This dissertation is motivated by the need to better quantify and understand tsunami hazards affecting the USEC by modeling tsunami generation, propagation, and coastal impact from extreme but realistic sources. The general goal of the thesis is to improve the scientific basis for tsunami hazard assessment by integrating physically based numerical simulations with hazard metrics that allow comparison across sources, regions, and return periods. The dissertation is structured as three journal articles, each addressing a complementary aspect of tsunami hazard, with increasing complexity in source characterization and analysis.
The first two papers, which form manuscripts 1 and 2 of this dissertation, focus on regional scale tsunami hazard assessment along the USEC from extreme seismic and non seismic sources in the North Atlantic. These manuscripts establish the methodological framework used throughout the thesis and provide the foundation upon which the third manuscript is built.
Manuscript 1 is based on the 2022 paper, which investigates tsunami coastal hazard along the USEC generated by coseismic sources located in the A¸cores Convergence Zone and the Puerto Rico Trench/Caribbean arc areas Tsunami coastal hazard 2022. In this study, a collection of large magnitude (M8-9) earthquake scenarios is parameterized using available seismo-tectonic and historical data. Tsunami generation and propagation are simulated using the fully nonlinear and dispersive model FUNWAVE-TVD, implemented through nested grids covering the North Atlantic basin and the USEC. Coastal hazard is quantified using four physically meaningful metrics maximum surface elevation, current velocity, momentum force, and tsunami arrival time computed along the 5-m isobath. These metrics capture different dimensions of the impact of the tsunami relevant to flooding, navigation, structural damage, and evacuation. A tsunami intensity index is then introduced to combine these metrics into a single comparative measure of hazard. This manuscript demonstrates that, despite the long propagation distances involved, far field coseismic sources can produce spatially coherent patterns of tsunami hazard along the USEC, strongly modulated by shelf bathymetry and wave refraction.
Manuscript 2 is based on the 2025 paper, which extends the regional hazard framework to include a broader range of extreme tsunami sources and introduces a limited probabilistic tsunami hazard analysis (PTHA) for the USEC Tsunami hazard assessment 2025. Building upon the deterministic modeling approach developed in the first paper, this study simulates tsunamis generated by fourteen probable maximum tsunami scenarios, including large earthquakes, submarine mass failures, and volcanic flank collapses distributed across the North Atlantic basin. Using consistent numerical models and nested grids, hazard metrics are computed and combined into integrated alongshore representations of tsunami impact. Estimated return-period ranges are then assigned to each source based on existing literature and expert judgment, enabling a first order probabilistic assessment of tsunami hazard along the USEC. The results highlight specific coastal regions where wave focusing consistently amplifies tsunami impacts across multiple sources, and they demonstrate how tsunami hazard increases with return period from negligible levels to impacts comparable to severe coastal storms. This chapter emphasizes both the feasibility and the necessity of moving toward comprehensive probabilistic tsunami hazard assessments for the USEC.
Across these two chapters, my primary contribution was the execution and analysis of the tsunami simulations for the selected sources. I was responsible for performing numerical simulations of tsunami generation and propagation using state of the art models, processing model output, and analyzing the resulting hazard metrics to assess spatial patterns of coastal impact. My work focused on ensuring physical consistency across simulations, combining results across multiple source types, and interpreting model outputs in the context of regional tsunami hazard assessment.
The third manuscript of the dissertation builds upon the methodologies and insights developed in the first two manuscripts by applying them to a historically documented and complex tsunami event: the 1883 Krakatau eruption. Unlike the regional hazard studies of the USEC, this manuscript focuses on reconstructing tsunami source processes associated with volcanic eruptions, including explosive activity, caldera collapse, and pyroclastic density currents. To generate and propagate the tsunamis, a combination of two numerical models is used: the three-dimensional non-hydrostatic wave model NHWAVE and the two-dimensional Boussinesq wave model FUNWAVE-TVD. Both models address the physics of wave frequency dispersion. By modeling tsunami generation mechanisms constrained by geological and historical observations, this final chapter extends the thesis from regional hazard assessment to a process based understanding of tsunami generation from volcanic sources. In this manuscript, my primary contribution consisted of performing the initial numerical simulations used to investigate tsunami generation mechanisms associated with the 1883 Krakatau eruption. I developed and implemented the first set of model simulations that explored the potential source processes and their resulting tsunami characteristics. These simulations served as the starting point for the modeling framework, which was later refined and expanded by other members of the research team using improved versions of the numerical models, including an updated implementation of NHWAVE. In addition to conducting the initial simulations, I contributed figures derived from the model results and assisted in preparing portions of the manuscript that describe the modeling methodology and results.
Together, the three manuscripts form an integrated set of work that advances tsunami science by linking detailed numerical modeling with hazard assessment across a spectrum of tsunami sources. The first two manuscripts establish a consistent framework for evaluating tsunami hazard at regional scales, while the third manuscript deepens the physical understanding of tsunami generation mechanisms. Collectively, this dissertation contributes to improving tsunami hazard assessment and preparedness for regions traditionally considered to be at low risk, while also demonstrating that tsunamis have occurred throughout history.
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.
Recommended Citation
Mohammadpour, Maryam, "NUMERICAL INVESTIGATION OF TSUNAMI GENERATION, PROPAGATION, AND COASTAL HAZARD FROM VOLCANIC AND TECTONIC SOURCES" (2026). Open Access Dissertations. Paper 4552.
https://digitalcommons.uri.edu/oa_diss/4552