Annualmeeting:2017 CSDMS meeting-042

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Observable tsunami deposit layers and tsunami inundation

Hui Tang, Virginia Tech Blacksburg Virginia, United States. tanghui@vt.edu
Robert Weiss, Virginia Tech Blacksburg Virginia, United States. weiszr@vt.edu


[[Image:|300px|right|link=File:]]Recent post-tsunami field surveys show that sandy tsunami deposits usually cannot cover all of the tsunami flow inundation areas. The difference between the sandy tsunami deposits inland extent and the flow inundation limit can be used to estimate tsunami magnitude. However, the relationship between tsunami deposit inland extent and inundation limit is still not fully understood. This paper focuses on studying the relationship and its control factors by using a parameter study and field measurements. Deposition ratio is a ratio between the sediment layer inland extent and the tsunami inundation limit to quantify this relationship. In the parameter study carried by a state-of-the-art sediment transport model (GeoClaw-STRICHE), we change grain size, offshore wave height, and onshore slope. The deposition ratio for tsunami deposit extent ($\xi_0$) is not sensitive to the grain size. However, the deposition ratios for observable sediment layer inland extent ($\xi_{0.5}$ and $\xi_{1}$) are affected by the grain size, offshore wave height, and onshore slope. The deposition ratios for a 0.5 cm thick sediment layer from parameter study are consistent with field measurements from the 2011 T\={o}hoku-oki tsunami on Sendai Plain. The topography, especially onshore slope, strongly influences the deposition ratio in this case. The combination of different deposition ratios can be used to estimate tsunami inundation area from tsunami deposits and improve tsunami hazard assessments.