The assumed data on wave source used in the above simulation is as indicated in the following. Data is assumed based on the studies of past earthquakes and tsunami.
･Magnitude of the earthquake: M=7. 8 (the largest earth-quake which caused tsunami in the Sea of Japan.)
･Number of waves sources studied: 6
･After tsunami were simulated based on the 6 wave sources, the one with the largest calculated runup height was selected for use in the simulation examination.
(2) Mooring facilities as centers of marine transportation
When a disaster occurs, mooring facilities in the port play an important role in transporting emergency goods and marine transportation in the case of evacuation. Okushiri Port is not only the gateway to Okushiri Island, but also is particularly important as the key port for marine transportation during emergencies and disasters. The reinforcement and improvement of mooring facilities in the port is important to secure transportation, and it is necessary to reinforce and improve mooring facilities so that they can withstand earthquakes.
?Examination of key facilities for marine transportation during emergencies and disasters
The present layout of Okushiri Port is as indicated in Fig.
4- 1. Along with restoration construction, the present ferry quaywall (-5.0m) was improved to be more quakeand liquefaction- resistant. In addition, the quaywall, which is currently under construction, is being improved as an earthquake- resistant reinforced quaywall. Because of this, these 2 facilities should be regarded as the key facilities for marine transportation, and improvement of these facilities and their hinterland access roads should be promoted.
?Considerations for the entrance of emergency vessels immediately after an earthquake
Because tsunami waves flowed into the port during the Hokkaido Nansei- Oki Earthquake, which resulted in numerous objects floating and being submerged in the port and in front of the quaywalls, large rescue vessels could not enter the port until safety in the port was confirmed. This resulted in mooring these vessels offshore outside of the port and in transporting the evacuees by barge, which was very dangerous during embarking and disembarking. It is desirable, therefore, to establish measures to ensure rescue activities to be conducted within the port where the water is calm, at least temporarily, until sufficient water depth is confirmed at quaywalls and elsewhere. For this purpose, the outlying facilities established near the mouth of the port whose calmness is assured, which are believed to be least influenced by floating and submerged objects, and whose water depth required for mooring large vessels (3, 000- class) used for disaster recovery is readily secured, should be regarded as temporary mooring facilities at the time of emergency to be utilized effectively.
The facility areas which correspond with assumed ship dimensions are shown in Fig. 4-3.
?Consideration of the allocation of fenders
･Fenders should be allocated densely so that small vessels, including barges belonging to the Maritime Safety Agency and fishing boats, can be moored at earthquake- resistant quaywalls and other mooring facilities.
･Ramps should be placed so that several small vessels (each with a length of approximately 10m) can be moored together in order to enable smooth rescue operations.
Fig.4-3 Potential temporary mooring areas(current port layout)
