Tsunami Mapping Project,
Department of Ocean & Resources Engineering,
School of Ocean and Earth Science and Technology (SOEST),
University of Hawaii at Manoa,
Honolulu, HI, USA,
Resonance amplification of tsunami waves over an insular shelf and fringing reefs:
The 2009 Samoa Tsunami resulted in severe damage and inundation at Tutuila, American Samoa. The disparity of the impact and the varying accounts of the tsunami along the coast remain one of the most intriguing aspects of the event. We utilize a non-hydrostatic, dispersive wave model with a 4-layer nested grid to reconstruct the tsunami from the earthquake source for understanding of the wave dynamics around Tutuila. After validation with water-level measurements, a Fast Fourier Transform of the computed surface elevation reveals coupled resonance oscillations between 3 and 18 min period over the insular slope and shelf as well as the fringing reefs. The resonance, which focuses energy according to shelf and embayment configurations, provides an explanation of the runup data and eyewitness accounts and identifies the coastal communities prone to tsunami hazards.
The 2009 Samoa Tsunami serves as a benchmark study of tsunami risks for island communities around the world. Though the western side of the island facing the tsunami source saw the highest runup, severe wave impact and destruction are evident along the eastern and northern shores of the island.
The shallow reefs, in some instances, provided little protection to the coastal communities and transformed the tsunami waves into more dangerous conditions. The knowledge of local wave resonance is of greater importance to hazard mitigation than the origin and direction of the tsunami. Even without detailed information of the tsunami source, implementation of the presented methodology with hypothetical events can provide insights of potential tsunami threats for emergency planning and management.
The animation shows the free surface elevation of the third layer with exaggerated vertical scale for illustration purposes.
The numerical model NEOWAVE, developed by Yamazaki et al. 2009, is used to update the tsunami evacuation maps around Hawaii and American Samoa. Further research with NEOWAVE is conducted in Puerto Rico and Chile.
More information on numerical models developed by the ORE Tsunami Mapping Project:
Roeber, V., K.F. Cheung, and M.H. Kobayashi (2010), Shock-capturing Boussinesq-type model for nearshore wave processes, Coastal Engineering, 57(4), 407-423.
Yamazaki, Y., Z. Kowalik, and K.F. Cheung (2009), Depth-integrated, non-hydrostatic model for wave breaking and runup, Int. J. Num. Meth. Fluids, 61(5), 473-497.
Yamazaki, Y., K.F. Cheung, and Z. Kowalik (2010), Depth-integrated, non-hydrostatic model with grid nesting for tsunami generation, propagation, and run-up, Int. J. Num. Meth. Fluids, in press.
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TSUNAMIby INGVterremoti38,858 views
if this is real..and i am on that island..i assure, i'm dead! nice sector of research!
happinesson 2 months ago
:O
MrCocaines 9 months ago