Probabilistic Tsunami Hazard Assessment for Local and Regional Seismic Sources Along the Pacific Coast of Central America with Emphasis on the Role of Selected Uncertainties
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Historical data indicate that the Middle America subduction zone represents the primary tsunamigenic source that affects the Central American coastal areas. In recent years, the tsunami potential in the region has mainly been assessed using maximum credible earthquakes or historical events showing moderate tsunami potential. However, such deterministic scenarios are not provided with their adequate probability of occurrence. In this study, earthquake rates have been combined with tsunami numerical modeling in order to assess probabilistic tsunami hazard posed by local and regional seismic sources. The common conceptual framework for the probabilistic seismic hazard assessment has been adapted to estimate the probabilities of exceeding certain tsunami amplitudes along the Central American Pacific coast. The study area encompasses seismic sources related to the Central America, Colombia and Ecuador subduction zones. In addition to the classical subduction inter-plate events, this study also incorporates sources at the outer rise, within the Caribbean crust as well as intra-slab sources. The study yields conclusive remarks showing that the highest hazard is posed to northwestern Costa Rica, El Salvador and the Nicaraguan coast, southern Colombia and northern Ecuador. In most of the region it is 50 to 80% likely that the tsunami heights will exceed 2 m for the 500 year time exposure (T). The lowest hazard appears to be in the inner part of the Fonseca Gulf, Honduras. We also show the large dependence of PTHA on model assumptions. While the approach taken in this study represents a thorough step forward in tsunami hazard assessment in the region, we also highlight that the integration of all possible uncertainties will be necessary to generate rigorous hazard models required for risk planning.
KeywordsSeismic segmentation earthquake rates tsunami hazard Central America Colombia Ecuador subduction zones
This study was possible thanks to the financial support to NZ from the Helmholtz Association and the GeoSim Program and the GeoForschungsZentrum (GFZ-Potsdam). Deep thanks to B. Benito, Y. Torres, A. Rivas and R. García at the Politechnic of Madrid (UPM) for hosting NZ during the Central American PSHA Workshop held in 2011 and for the discussions on the probabilistic framework. Special acknowledge to W. Rojas, E. Molina, E. Camacho for discussions related to Central American seismic catalog and seismic rates of the region. M. Fernández is acknowledged for discussions of the Central America tsunami catalog. A. Hoechner is acknowledged for the fruitful discussions about PTHA uncertainties. M.Sørensen and L. Matias are acknowledged for comments on a first stage of the study. Most figures were drawn using the GMT software Wessel et al. (2013) and R-project (R Core Team 2014). We strongly appreciate the comments and suggestions of two anonymous reviewers and the guest editor of the special volume E. Okal.
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