Abstract
Abstract. This study investigates the issues related to underestimation of the earthquake source parameters in the context of tsunami early warning and tsunami risk assessment. The magnitude of a very large event may be underestimated significantly during the early stage of the disaster, resulting in the issuance of incorrect tsunami warnings. Tsunamigenic events in the Tohoku region of Japan, where the 2011 tsunami occurred, are focused on as a case study to illustrate the significance of the problems. The effects of biases in the estimated earthquake magnitude on tsunami loss are investigated using a rigorous probabilistic tsunami loss calculation tool that can be applied to a range of earthquake magnitudes by accounting for uncertainties of earthquake source parameters (e.g., geometry, mean slip, and spatial slip distribution). The quantitative tsunami loss results provide valuable insights regarding the importance of deriving accurate seismic information as well as the potential biases of the anticipated tsunami consequences. Finally, the usefulness of rigorous tsunami risk assessment is discussed in defining critical hazard scenarios based on the potential consequences due to tsunami disasters.
Highlights
Tsunami hazard maps and early warning systems are essential for mitigating the consequences of catastrophic tsunami disasters
Issuing accurate and prompt tsunami warnings is vital for reducing the potential consequences due to catastrophic tsunami disasters
Recognizing the unavoidable uncertainty in the estimation of earthquake information that is used for tsunami early warnings as well as the uncertainty of the earthquake rupture process, it is important to evaluate the effects of such uncertainties on the tsunami risk predictions quantitatively
Summary
Tsunami hazard maps and early warning systems are essential for mitigating the consequences of catastrophic tsunami disasters. By analyzing the estimated tsunami loss for coastal cities and towns in Miyagi Prefecture, potential biases due to underestimation of earthquake magnitude can be quantified These results provide useful insights regarding the importance of deriving accurate seismic information and can be compared with the effects due to uncertain source characteristics (e.g., geometry and spatial slip distribution) for given moment magnitudes, which is unavoidable in making risk predictions based on macroscopic earthquake parameters only. For this purpose, a new probabilistic tsunami loss model for large Mw8.0+ earthquakes in the Tohoku region of Japan is developed. Sub-fault size: 10 km by 10 km Shaded areas: Shallow segment (top-edge depth < 20 km)
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