TRANSFORMATION OF TSUNAMIS IN A COASTAL ZONE

In order to obtain fundamental information to establish warning practices and effective countermeasures against the tsunamis on the coast, the authors have studied on refraction of the tsunamis propagating into Osaka Bay and on tsunami spectra. ^he refraction of the tsunami is studied by a numerical computation for a program of refraction and shoaling of small amplitude wave. An example is shown for Chilean Tsunami in I960 to reveal that the refraction is an important factor to study on the tsunami wave height distribution along the coast of Kii Peninsula and Shikoku Island. The mareograms of the tsunamis are analyzed to obtain power spectra to study on transformation of the tsunamis from the Pacific ocean to the head of Osaka Bay. The result suggests that it is necessary to be careful to study on transformation of the tsunamis with use of the refraction diagram because the tsunami is not a simple monochromatic and small amplitude plane wave. A brief remark is given for the analysis of the tsunami as non-stationary process.

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Tsunami Attack Evaluation and Countermeasures for Moored Small Ships in a Port

Volume 6: Ocean Engineering ◽

10.1115/omae2011-49800 ◽

2011 ◽

Author(s):

Eiichi Kobayashi ◽

Kouhei Yurugi ◽

Shunichi Koshimura

Keyword(s):

Ship Motions ◽

Mooring Lines ◽

Osaka Bay ◽

Small Vessels ◽

High Tension ◽

The Pacific ◽

Horizontal Flows ◽

The Face ◽

The Pacific Ocean ◽

Marine Disaster

There is increasing concern over the possibility of the occurrence of huge Toukai, Tonankai, and Nankai earthquakes in the Nankai Trough, located in the Pacific Ocean off Japan. It is estimated that there is a 50% probability of a tsunami being generated by an earthquake in this area over the next 30 years. A tsunami attack on the coast of Japan would not only increase the sea level, but would also create strong horizontal flows in bays and ports. In particular, along the coastal area of Osaka Bay, Japan, there are numerous small ports where pleasure ships and/or fishery boats are moored. Any small ships moored in these ports would be subject to violent motion by strong lateral flows, even if they are moored to each other. As a consequence, the mooring lines would be cut, ships would move uncontrollably, and causing damage to facilities. Thus, it is very important from the viewpoint of marine-disaster prevention to gain a better understanding of the motion of small vessels originating in tsunami flows and to develop countermeasures in the face of a tsunami attack. In this paper, basic analyses of the ship motions resulting from a tsunami attack are carried out, and possible countermeasures are investigated. First, we describe mathematical models approximating the flow of tsunami and the abrupt maneuvers of relatively small vessels while being moored. Next, numerical simulations of the lateral motion of moored ships resulting from a tsunami attack on a fishery port located in the Osaka Bay are carried out. Additionally, the possibility of relatively high tension to be generated along the mooring lines is evaluated. Finally, the results of computer simulations demonstrate that such hazardous phenomena can be addressed with appropriate countermeasures.

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A COMPARISON OF NATURE WAVES AND MODEL WAVES WITH SPECIAL REFERENCE TO WAVE GROUPING

Coastal Engineering Proceedings ◽

10.9753/icce.v17.177 ◽

1980 ◽

Vol 1 (17) ◽

pp. 177 ◽

Cited By ~ 2

Author(s):

Hans F. Burcharth

Keyword(s):

Phase Distribution ◽

Random Phase ◽

Power Spectra ◽

Height Distribution ◽

Wave Group ◽

Storm Waves ◽

Wave Height Distribution ◽

Storm Wave ◽

Wave Heights ◽

The Impact

This paper represents a comparative analysis of the occurrence of wave grouping in field storm waves and laboratory waves with similar power spectra and wave height distribution. Two wave patterns - runs of waves and jumps in wave heights - which have significant influence on the impact on coastal structures were included in the analysis of storm wave records off the coasts of Cornwall, U.K. and Jutland, Denmark. Two different laboratory wave generator systems, based on random phase distribution of component waves, were used. Within the limitations given by the relatively small number of analysed records it is shown that wave group statistics can be satisfactorily reproduced by random phase generators that are not based on a limited number of component waves, but for example based on filtering of white noise. It is also shown that the statistics of large waves and wave groups containing large waves depend on whether the waves are defined from zero-upcrossings or zero-downcrossings. Although very similar seas were chosen for the analysis it was found that significant differences in the wave group statistics from the two locations existed. Also a considerable scatter in the wave group statistics throughout the storms was found.

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FODBL STUDY OF TRANSFORMATION OP TSUNAMIS IN URADO BAT

Coastal Engineering Proceedings ◽

10.9753/icce.v12.126 ◽

1970 ◽

Vol 1 (12) ◽

pp. 126

Author(s):

Shigehisa Nakamura ◽

Yuichi Iwagaki ◽

Yoshito Tsuchiya

Keyword(s):

Experimental Study ◽

Pacific Ocean ◽

Hydraulic Model ◽

Horizontal Scale ◽

The Pacific ◽

The Pacific Ocean ◽

Chilean Tsunami ◽

The City

For the city and harbour of Kochi, including Urado Bay, facing the Pacific Ocean, an experimental study has teen carried out on the problem of protection from tsunami disasters, and future harbour planning; that is, dredging, reclamation and construction of breakwaters against tsunamis. A hydraulic model of horizontal scale 1/250 and vertical l/lOO was used according to Froud's similitude. The transformation of the design tsunami m the hay was studied to find the effect of the tsunami breakwaters, dredging and reclamations by use of the model which was able to reproduce the Chilean Tsunami.

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