博士 / 國立臺灣海洋大學 / 海洋環境資訊學系 / 96 / Abstract
The whole world has been shocked by the tsunami happened in South Asia in 2004 and eager to establish effective countermeasures. Few disastrous tsunamis ever occurred in Taiwan around one hundred years ago, the Coast Guard Administration thus bears the responsibility as the first-tier execution organization for disaster prevention and mitigation before and after the attack of a tsunami. For that, countermeasure policy must be drafted upon scientific knowledge. This dissertation accordingly reviews the related policies against tsunami in the U.S.A. and Japan, and then approaches upon science to how the Coast Guard cutters in our country react to a tsunami alarm. Finally, characters of cutters and their ports of call are analyzed to draft a principle of on-the-sea evacuation for reserving the capability of returned rescue along the coast. This work thus can be viewed as a model to establish the local tsunami countermeasure policy for various regions and harbors.
For those purposes, 51 severe earthquake events reached Richter 6.0 in and around Taiwan in 1990-2006 are inspected. Out of them, however, only 5 events were found to be associated with water level anomalies in the 6-minute tide data from several tidal gauges of the Central Weather Bureau and other institutes. Together with some other abnormal records for earthquakes in far Pacific Ocean, a total of 41 time series of tides has been processed for high passed signals of tsunami beings. Oscillations with periods of about 20 minutes might last for few hours and had amplitudes of around 60 cm for maximum and less than 20~30 cm mostly. Although those events had not reached a level of catastrophe, they provide valuable learning opportunity for tsunami propagating in Taiwan waters.
The 41 tsunami series can be divided into 3 categories upon epicenter of earthquake: (1) The 921 Chi-Chi earthquake on the central land of Taiwan causing a tsunami signal in Hualien in a time lag of about half hour would be an attractive but bizarre case. (2) The earthquakes in near sea mostly occurred in east of Taiwan, sometimes causing Tsunami only at part of the coast, sometimes spreading across the east coast to even detour around Eluanbi to the south of Taiwan Strait. Besides, wave reflection by Suao Ridge seemed happened. Twin earthquakes occurred in south of Taiwan in 2006, creating very unique characters of tsunami. The tsunami propagated in Taiwan Strait to Pong-hu ranked the simplest. (3) The far range earthquakes in Pacific Ocean could form a tsunami of 50cm. The wave propagation over the ocean might be related to the reflection of islands arc.
The COMCOT (Cornell Multi-grid Coupled Tsunami) Model is used to simulate tsunami waves propagating in the sea at north of Taiwan. The tsunami ripple expands from continental shelf to slope with amplitude declined by depth getting shallow, while on the contrary, the amplitude of the ripple in continental shelf may not be increased because the bottom friction effect overcomes the water shallowness, but would result in amplitude enhancement with energy gathered at underwater plateau indicated by protruding contours. Therefore the distribution of tsunami amplitudes at outer sea requires diversified simulations from various epicenters and scales of earthquake. The database thus provides the prompt information for Coast Guard cutters to decide an appropriate spot at sea to go within very limited time after a tsunami warning.
There is still short of complete contingency plan for tsunami attack by both our central and local governments, which is not as complete as established in the U.S.A. and Japan. The research and discussion of our tsunami disaster prevention plan is still unsatisfactory and need more attention and active effort. The contingency plans of the U.S.A., Japan and other countries are focused on prevention and mitigation of coastal community and lack of vessel contingency plan. The ROC Coast Guard has more than 170 various cutters. This dissertation in particular, is to analyze the mobility of those cutters, endurance and the environment of port of call, and to propose countermeasures of disaster prevention and relief for normal vessels and Coast Guard cutters with guidelines established as reference for related offices.
| Identifer | oai:union.ndltd.org:TW/096NTOU5282010 |
| Date | January 2008 |
| Creators | Lin, Ching-Long, 林欽隆 |
| Contributors | Hu, Jian-Hwa, Wu, Tong-Min, 胡健驊, 吳東明 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 313 |
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