Measures against Earthquakes and Tsunamis in Okushiri Port
Hideyoshi Yanagida Hokkaido Development Bureau
Takashi Arata Cold Region Port and Harbor Engineering Research Center
Yuichi Kumashiro Public Consultants Co. Ltd.
Shuji Mifune Nihon Data Service Co., Ltd.
Masato Yoshiura North Japan Port Consultants Co., Ltd.
ABSTRACT
The Hokkaido Nansei- Oki Earthquake, which occurred at 22:17, July 12, 1993, caused serious damage on the southern shores of Hokkaido along the Sea of Japan, not only from the quake itself but also from large- scale tsunami. Okushiri Island, which was near the seismic center, had a particularly large number of casualties from the earthquake and tsunami (a record number for the island) and, in addition, people experienced serious disruption to their daily lives, including from damage to houses, roads, river and port facilities, and other lifelines. Many lost their lives and property. Furthermore, as many as 4 earthquakes, including the Hokkaido Nansei-Oki Earthquake, have struck Hokkaido in the past 2 years: the Kushiro-Oki Earthquake of January 15, 1993; the Hokkaido Toho- Oki Earthquake of October 4, 1994 and the Sanriku- Harukaoki Earth-quake of December 28, 1994. In addition to these earthquakes, the Hanshin- Awaji Great Earthquake, the largest earth- quake since World War II, struck the Hanshin- Awaji area on January 17, 1995. These serious earthquakes led us to recog- nize the importance of ports and harbors in times of disasters. The aim of this study is to build ports and harbors more resis- tant to disasters to achieve the following: to secure the safety and property of residents around Okushiri Port, which is the only local port and is "the gateway to the island;" to give suggestions regarding Okushiri's regional disaster- prevention plans for hi- ture improvement of ports and harbors and works in the surrounding areas (such as roads and seashores) based on concrete ex- aminations of the 3 areas, including disaster- prevention facilities, regional disaster- prevention plans and disaster- prevention systems; and to contribute to the improvement of safety of people who live on remote islands. It is also believed that the re- sults of this study will contribute greatly to people not only in Japan but also elsewhere when they establish measures against earthquakes and tsunami on remote islands.
1. Introduction
Okushiri Island, the westernmost island of Hokkaido, is an island in the Sea of Japan approximately 61km northwest of the town of Esashi, with a circumference of 84 km.
Okushiri Port, which is said to be "the gateway to Okushiri Island," was designated as a harbor of refuge in 19 51. Since then, it has served as the base of the fishing in- dustry in the Sea of Japan. Commercial activities such as un-loading related goods and shipping marine products have al-so developed. In 1966, the port was designated as a local port of the area. In 1967, the car ferry route was estab-lished, which contributed greatly to the development of the island and stable lives of the islanders as the commerce port for daily necessities of the residents of the remote islands and goods necessary for production and commercial activi-ties. Although the Hokkaido Nansei- Oki Earthquake of 1993 caused serious damage to the port and harbor facilities and interfered greatly with daily life and commercial activities on the island, immediate restoration activities allowed the ferry line to reopen only 4 days after the earthquake, and the port was completely restored in March 1995. The town of Okushiri finalized the Okushiri Port Marine Town Project (MTP) in March 1994. However, the project was not intended to improve the port in terms of earthquake and tsunami resistance, so fundamental re- examination is necessary before determining the 9th 5year port implementation plan.
In this study, ways to improve ports and harbors for greater resistance to disasters will be examined, items of note regarding disasters and their prevention measures will be suggested, and listed items concerning port and harbor disaster- prevention measures will be suggested regarding Okushiri Town's regional disaster- prevention plans.
2. Fundamentals of disaster-prevention measures against earthquakes and tsunamis
At present, the establishment of a set of comprehensive disaster- prevention measures is needed, which are based on the 3 pillars: disaster- prevention facilities, regional disaster- prevention plans and disaster- prevention systems.
Disaster- prevention facilities are those built to prevent tsunamis from coming inland or to reduce the degree of tsunamis striking inland. The limited effectiveness of suchfacilities, however, must be acknowledged.
The regional disaster- prevention plans are, in short, intended to make the town along the shore more disaster- resistant through a long-term project. Today, development of areas along the shore is progressing and even the topography of such areas greatly changes due to reclamation. In such cases, the predominant emphasis becomes "the creation of a town of convenience" and the goal of "making the town more disaster-resistant" is likely to become obscured.
Development and disaster prevention have to be 2 wheels on an axis in terms of the conditions for the existence of the urban areas along the shore.
The disaster- prevention system is intended to at least save all human lives by establishing a disaster- prevention culture to be handed to future generations, encourage residents to behave in accordance with tsunami forecasts and warnings and prepare residents in all possible ways so that immediate rescue operations can be possible in emergencies.
In this study, based on the aforementioned 3 pillars, problems relating to earthquake and tsunami disaster prevention were extracted from the present state of the earthquake condition, and reference materials, newspaper reports and hearings in the town regarding earthquake and tsunami disaster- prevention measures, Classified and summarized results are shown in Table 2- 1.
