ABSTRACT:

This paper aims to investigate the kinetic momentum of ice floe carried by tsunami through the experiments. In the experiment, two types of model slope were installed into the wave tank of 24m in length and solitary wave were generated. And the movement of model ice sheets was observed by video camera. The model ice sheets were made of polypropylene of which the friction coefficient against the bottom of model slope was about the same as that of ice floe and sandy beach.

INTRODUCTION

The Sea of Okhotsk coast of Hokkaido is covered with ice floes every year. Fig.1 shows the area covered by ice floes. In years when many ice floes exist, they reach the Pacific coast via the Nemuro Straits. On March 4, 1952, a large earthquake (M = 8.0) occurred and caused serious damage in the eastern part of Hokkaido. The earthquake is known as the Tokachi-oki Earthquake (Long. 143° 52' E, Lat. 42° 09'N). At the time of the Tokachi-oki Earthquake, tsunami of 1 to 3 m in wave height hit the entire coast extending from Hidaka Higashi Beach and Cape Erimo to Nemuro. The scale of tsunami was not very large and serious damage was not expected. Houses in Kiritappu Town were, however, hit by ice floes that ran up on land with the rise of water level by tsunami, due to the fact that the town is situated on a tombolo (Fig. 1) between Hamanaka and Biwase bays, its center is situated on lowland approximately 2 m above sea level and the tsunami coincided with the ice floe season in winter. Personal and physical damage was therefore increased. In the stricken Kiritappu area, breakwaters have now been established to prevent such damage in the future.

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